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polymeric composite for the design of liquid storage tanks
Materials and Design 36 (2012) 847–853
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Materials and Design journal homepage: www.elsevier.com/locate/matdes
Suitability of using coir fiber/polymeric composite for the design of liquid storage tanks B.F. Yousif ⇑, H. Ku Centre of Excellence in Engineered Fiber Composites (CEEFC), Faculty of Engineering and Surveying, University of Southern Queensland, QLD 4350, Toowoomba, Australia
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Article history: Available online 17 March 2011 Keywords: Coir fiber Polyester Water Interfacial adhesion SEM and pull-out tests
a b s t r a c t Single fiber pull-out test is employed experimentally to model the interfacial adhesion characteristics of natural fibers with synthetic resin. The current study investigates the possibility of using coir fiber as reinforcements for polyester composites under aging process. The main application would be in designing tanks storage for different types of liquid. A single fiber pull out samples were soaked in seven different solutions (water, salt water, gasoline, diesel, break oil, engine oil, and power staring oil) for 6 months, and the pull-out tests were then carried out. Scanning electron microscopy (SEM) was used to examine the damage features on the samples. The results revealed that the highest amount of liquid absorbed was water, followed by salt water, which is due to the low viscosity of those liquids compared to other liquids. In spite of that, the highest interfacial adhesion property was found in samples soaked in salt water, which was about 120 MPa followed by water. SEM images showed that no pulling out process taking place during the test indicating high interfacial adhesion properties of coir fibers to the polyester. However, the differences in the interfacial adhesion properties are due to the deterioration in the fiber strength during the aging process. Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction Natural fibers are becoming an attractive alternative over synthetics fibers due to their advantages such as recyclability, biodegradability, renewability, low cost, light weight, high specific mechanical properties and low density [1–10]. Nowadays, applications of natural fibers reinforced polymeric composites can be found in housing construction material, industrial and automotive parts. From a mechanical point of view, natural fibers are good candidates for polymeric composites, i.e. low density, high strength, high flexural modulus, and high impact strength [2–7]. However, there is a limitation in the usage of natural fibers concerning their interfacial adhesion with matrix. Furthermore, it has been reported that interfacial adhesion of fiber to the matrix played the main role in controlling the mechanical properties of the composites [1,4,10– 14,19,20]. Untreated oil palm, jute, sugarcane, and banana fibers have very poor interfacial adhesion strength with polyester [1,18,19]. This poor interfacial adhesion is a result of foreign impurities/substances that prevents the matrix from bonding firmly with the fibers [1]. Single fiber or filament pull out technique has been used to model the failure of a composite material [15]. The interpretation of this model, however, varies between laboratories. Research, in the area of fiber pull out, has considered the fracture mechanics and shear stresses of fiber–matrix failure [15–17]. Var⇑ Corresponding author. E-mail addresses: [email protected] (B.F. Yousif), [email protected] (H. Ku). 0261-3069/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.matdes.2011.01.063
ious fiber/resin combinations and many sample configurations have been used in the single fiber models. ‘Fibers’ of interest embedded in matrices and subjected to tensile load [4]. Stress/ strain results indicate the interfacial adhesion characteristic of the fibers with the matrices. From the reported works, coir fibers showed very high interfacial adhesion properties under dry conditions. However, in real applications, products made of polymeric composite could be exposed to different environmental circumstances. For example, tanks could be filling in with water, salty water, gasoline, or other types of liquid. Understanding of the interaction and interfacial adhesion between the fibers and the matrix has not been explored yet. This motivates the current study on the interfacial adhesion characteristics of coir fiber with polyester matrix under different aging solutions. Furthermore, the potential application for such materials could be for vessels and tanks containing water, salty water, gasoline, diesel, brake oil, or power steering oil. Prepared single fiber pull out samples were immersed in different types of liquid for 6 months before being taken out for experiments. After this, samples were dried, tested, and then surface observations were conducted. 2. Materials and experimental details 2.1. Samples’ preparation Raw coconut fruit is obtained from a farm in Melaka state, Malaysia. The coconuts are taken during the dry session, where less
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rain occurs and moisture content for the coconuts is less. The outer layer shell or the mesocarp of the coconut is considered for the current work. The coconut gathered is from the Arecaceae family of palm, particularly cocus nucifera, Fig. 1a. The coconut fibers are firstly pulled out from the husk, Fig. 1b. Practically, husks were soaked in water to ease the extraction of the fibers. The extracted fibers were washed again to remove the embedded dirt between the fibers, Fig. 1c. Finally, the fibers were dried at ambient temperature (32 °C) for 48 h. Each single fiber was carefully picked and examined using an optical microscopy. The coir fibers having average diameter (320 lm) were carefully selected, Fig. 1d. The chemical composition of coir fiber is 45% lignin, 42% cellulose and 5% water. In the fabrication process of the single fiber pull out samples, aluminum mold (12.7 mm 12.7 mm 50 mm) was used. Two pieces of hard rubber (thickness of 3 mm) were cut and carefully fixed at both ends of the mold. One of the rubber pieces was punched in the center with a needle to insert the coir fiber. Before pouring the polymer mixture into the molds, the molds was first sprayed with release agent ‘Orelube Non Paintable Mold Release’ and was left to dry. The polyester resin, mixed with 2% hardener, was carefully poured in the mold. All the prepared samples after pouring the polyester were kept at the same room temperature (24 °C) for 24 h. Due to the difficulties in controlling the fiber position, a stainless steel needle was used to hold the fiber until the mixture get into jelly conditions. Moreover, to avoid any errors in the test which could occurs due to the fabrication process, several samples were fabricated and then examined by naked eyes. The samples having any defects, due to the fabrication process, were eliminated. The bonding between the fiber and the matrix could be chemical and/or mechanical bonding [22]. For the current work, the bonding area between the fiber and the matrix was examined. Fig. 2b and c shows the surface of the fiber interaction with the matrix. The high intimate contact between the fibers and the matrix indicates chemical bonding. Moreover, in Fig. 2c, it seems that the fiber is filled by polyester which indicates a mechanical bonding between the fiber and the matrix, i.e. interlock. In other words, both types of bonding took place between the fiber and the matrix.
(a)
(c)
Twenty-eight specimens were selected, divided equally and immersed into seven containers containing seven different solutions. The solutions used were engine oil (Petronas MACH 5 SAE 40), power steering oil (BS Power Steering Fluid), brake oil (Petronas Brake and Clutch Fluid DOT 3), diesel (Petronas), gasoline (Petronas), water, and salt water (25% salt). The specimens were left in the solutions for 6 months at atmospheric temperature and pressure [5–8]. From the supplier database, the viscosity of the solutions is provided in Table 1. After aging process (6 months), the samples were taken out from the containers and dried under the sun for 8 h. The weights of each of the samples were measured before and after the aging using an electric weighing scale (±0.1 mg). 2.2. Experimental details It seems to be no standard of measuring the interfacial adhesion of fiber with matrix. However, every laboratory, thus, has developed their own methods with essentially the same idea and different procedures [20]. The current work based on the most common technique in the literature [1,4,10–14,19,20]. The interfacial adhesion characteristics of the coir fiber with polyester matrix are investigated using single fiber pull out technique, Fig. 2. In the experiments, Universal Tensile Test Machine Q100 was used for the pull out process. In the test, the polyester end of the sample was rigidly fixed on the machine. The second end of the sample (fiber) was tapped and then gripped in the machine with a gauging length of 20 mm. The pulling rate was set to be 1 mm/min and continued until the failure. For each aging condition (solution), the test was repeated four times and the average associated with maximum and minimum values are determined. The error percentage of the collected data is presented in Fig. 3. 3. Results and discussions The results of the current work are summarized in four subsections as: liquid absorption, pull-out results, SEM observations, and discussions.
(b)
(d)
Fig. 1. The extraction of the coir fibers process.
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(a)
(c)
(b)
Fig. 2. Schematic illustration of single coconut fiber pull-out test sample and micrographs of the fiber/polyester bonding area.
Table 1 Average viscosity of selected solutions.
Liquid absorption Viscosity (Centistokes)
Water Salt water Gasoline Diesel Brake oil Engine oil SAE 30-50
0.80 0.82 0.95 5.50 12.00 135.00
3
Grams
Solutions
3.5 2.5 2 1.5 1 0.5 0
16 14
Fig. 4. Liquid absorption of the samples.
12 10
% 8 6 4 2 0
Brake oil
Diesel Power steering oil
Gasoline
Engine Saltwater Water oil
Fig. 3. Error percentage between the peak values of all the specimens.
3.1. Liquid absorption Fig. 4 shows the liquid absorption for each of the seven (28 in total) samples. It can be found that the highest amount of liquid absorbed is water, followed by salt water. These are followed by
brake oil, gasoline, diesel, engine oil and power steering oil. It is important to be noted that the absorption rate is influenced by the solution type. Besides, the physical appearance of the fiber is affected by the long time immersing in the solution. It is observed, by the naked eyes, that the fiber color has faded especially in the case of water and salt water aging. For other solution, the fiber becomes dark brownish and split of fiber can be observed. It can be argued that the liquid absorption was inversely proportional to the density of the liquid. In addition, it seems that the viscosity of the solution plays a role in influencing the absorption rate of the samples. In other words, the lower the viscosity is the higher the absorption rate (cf. Table 1 and Fig. 4). Such differences in the absorption rate associated with some interaction between the fiber and the solution could result in remarkable differences in the put out results.
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3.2. Pull-out tests Fig. 5 illustrates the maximum stresses of the specimens soaked in different types of liquid of the pull-out tests. The highest ones were samples soaked in salt water (120 MPa); this was followed by water, diesel, engine oil, brake oil, power steering oil and gasoline (75 MPa). It can be found that there is no correlation between the amounts of liquid absorbed by the samples to the maximum stresses of the samples (Fig. 4). However, water and salt water topped the lists. This implied that though water and salt water are likely to bring least damaged to the material of the tanks even they are absorbed most. It can be argued that not much chemical attack has been made to the material by water and salt water. On the other hand, some chemical damages might have been done on the material by other types of liquid. This will be furthermore discussion in the SEM observation section. Fig. 6a shows the graph for the specimens soaked in brake oil. In general, the graph shows varied trends of pulling out for all specimens. The peak values of the tensile stress are between 80 MPa and 130 MPa. This large difference in peak values resulted in the large standard deviation for specimens in brake oil as compared to the specimens in the other solutions. Out of the four specimens, one specimen had a broken fiber and the fibers of the remaining three specimens were pulled out completely. The broken fiber might be due to a weak point in the fiber. For the pulled-out fibers, the curves show a repeated fluctuating pattern until the fibers were completely pulled out. This may be due to the fluctuating grip between the rough surface of the coir fiber and the polymer during the pull out process. Fig. 6b illustrates the curves for the specimens soaked in diesel, which shows a consistent trend for every specimen. There was a small fluctuation for two of the samples before reaching the peak value which might be because of the fluctuating grip between the coir fiber and the polymer during pull out. The peak values of the tensile stress lay between 100 MPa and 120 MPa. The consistency in the trend resulted in the lowest standard deviation for the specimens soaked in diesel as compared to specimens soaked in the other solutions. Fig. 6c shows the curves for the specimens soaked in gasoline. The trend of these specimens was almost similar to that of the specimens soaked in diesel; three of the specimens had their stressed increased gradually until the peak value was reached and then dropped down, indicating the complete pull out. The remaining one specimen fluctuated around the peak value until the fiber got completely pulled out. The peak values of the tensile stress of the specimens soaked in gasoline lie between 65 MPa and 90 MPa. Fig. 6d shows the graph for the specimens soaked in engine oil. Two of the specimens showed a gradual increase in tensile stress until the fiber broke, which was indicated by the sudden drop in the tensile stress after peak value. The fibers of the remaining two specimens were completely pulled out. The peak values for
Maximum stress, MPa
140 120 100 80 60 40 20 0
Brake oil Power Diesel steering oil
Gasoline Engine Saltwater Water oil
Fig. 5. Maximum stresses of samples.
the tensile stress of the specimens soaked in engine oil lay between 98 MPa and 118 MPa. Fig. 6e shows the graph for the specimens in soaked power steering oil. The peak values of the four specimens were between 74 MPa and 96 MPa. Out of the four specimens, the fibers of the three were completely pulled out, and the remaining one specimen had a broken fiber after reaching the peak value. For the pulled out specimens, two of them showed a sudden drop in tensile stress after peak value and the other one specimen showed a fluctuating decrease in the tensile stress. This might be due to the fluctuating grip between the rough surface of the coir fiber and the polymer during the pull out process. Fig. 6f illustrates the graph for the specimens soaked in saltwater. The peak values of the tensile stress for all four samples lay between 108 MPa and 132 MPa. All of the fibers of the four specimens were pulled out completely. Two of the specimens showed a fluctuating decrease in the tensile stress, which might be due to the previously mentioned fluctuating grip of the coir fiber on the polymer. Fig. 6g shows the curves for the specimens soaked in tap water. From the graph, it can be found that all the fibers of the four specimens were completely pulled out, with a fluctuating decrease in tensile stress. All the specimens soaked in tap water reached a peak value of tensile stress between 100 MPa and 120 MPa. The above results could be due to two reasons. Either there is a chemical reaction between the fiber and the solution which led to the deterioration of the fibers or weakening in the fiber due to the absorption of the solution. From Table 1, the lower viscosity of solutions was in the water, i.e. high absorption of solution occurs when the samples immersed in water. However, the pull-out results indicated that the maximum interfacial adhesion property took place when the samples immersed in water compared to other solution. In other words, it can be concluded that amount of adsorption does not highly influences the interface adhesion property of the fibers with the matrix compared to the type of the solution. From the information given above, it can be found that the composites of coir fibers and polyester is generally suitable for manufacturing the body of tanks for storing different types of liquid except gasoline, power steering oil and brake oil as indicated by the lower pull-out stresses. This will be further confirmed in the SEM observation section.
3.3. Scanning Electron Microscope (SEM) observations The pull-out results can be explained with the assistance of Scanning Electron Microscope (SEM) micrographs [9]. It should be mentioned here that no SEM image analysis could be performed with specimens soaked in brake oil because severe chemical reaction occurred between the polyester and the brake oil. Therefore, further study is recommended. In Fig. 7a, the micrograph of the sample soaked in diesel shows that failure occurred due to fiber breakage of fiber rather than pull out of fiber. This indicated that the coir fibers have very high interfacial adhesion properties to the polyester despite being immersed in the diesel. This supported the results displayed in Fig. 6b. Fig. 7b, the micrograph of the sample soaked in gasoline, illustrates that failure was also due to the breakage in fiber. However, the fiber breakage occurred further than the bonding area; the fiber broke inside the polyester. This could be due to a weak point in the fiber, which broke when the pulling out process was going on. Fig. 7c, the micrograph of specimen soaked in engine oil, shows that there was debonding, but no pull out. The failure in pull out occurred because there was an empty gap between the polymer and the coir fiber. The empty gap resulted in low interfacial adhesion between the polyester and the coir fiber. The reason for this empty gap could be due to improper preparation of the specimen
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(a) Brake oil Brake oil 1 Brake oil 2 Brake oil 3 Brake oil 4
100
120 100
Stress, MPa
120
Stress, MPa
(b) Diesel
140
140
80 60
80 Diesel 1 Diesel 2 Diesel 3 Diesel 4
60
40
40
20
20 0
0 0
10
20
30
0
40
2
4
6
8
10
Displacement, mm
Displacement, mm
(d) Engine oil
(c) Gasoline 100
140
90 120
70
100
Stress, MPa
Stress, MPa
80 60 50 40 Gasoline 1 Gasoline 2 Gasoline 3 Gasoline 4
30 20
80
40 20
10 0
0
2
4
Engine oil 1 Engine oil 2 Engine oil 3 Engine oil 4
60
0
8
6
0
1
2
3
4
6
5
7
Displacement, mm
Displacement, mm
(e) Power steering oil
(f) Saltwater
8
9
10
11
100 90
140
80
120
Stress , MPa
Stress, MPa
70 60 50 40 30 20 10 0
0
2
4
100 80 60
Saltwater 1 Saltwater 2 Saltwater 3 Saltwater 4
40
Power steering oil 1 Power steering oil 2 Power steering oil 3 Power steering oil 4 8 6
20 0
12
10
0
5
10
Displacement, mm
15
20
25
30
35
40
Displacement, mm
(g) Water 140
Water 1 Water 2 Water 3 Water 4
Stress, MPa
120 100 80 60 40 20 0
0
5
10
15
20
25
30
35
40
Displacement, mm Fig. 6. Graphs for the pull-out test.
in the mold. The presence of bubbles during preparation could also have caused the empty gap.
Similar to the specimen in Fig. 7c, the micrograph of specimen soaked in power steering oil, Fig. 7d shows that there was debond-
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Fig. 7. Scanning Electron Microscope images of samples.
ing, but no pulls out. The failure in pull out occurred because there was an empty gap between the polymer and the coir fiber. The empty gap resulted in low interfacial adhesion between the polyester and the coir fiber. The reason for this empty gap could be because of improper preparation of the specimen in the mold. The presence of bubbles during preparation could also have caused the empty gap. Fig. 7e, the micrograph of sample soaked in salt water, illustrates that there was complete pull out of inner fiber. Although the fiber was pulled out, not the entire bundle was successfully pulled out. There were some remaining fibers stuck to the polyester. This indicated that the coir fibers had very high interfacial adhesion properties despite being soaked in the salt water. This supported the results in Fig. 7e. In Fig. 7f, the micrograph of specimen soaked in tap water shows that there was an incomplete pull out of inner fiber. Although the fiber was pulled out partially, there was still some fiber stuck to the polyester. This indicated that the coir fibers had very high interfacial adhesion properties despite being immersed in the tap water. This supported the results in Fig. 7f. Yousif et al. fabricated a polyester composite based on betelnut fibers and measured the tensile strength of the fibers in dry and wet conditions using pull-out tests. They found that the maximum stress for the dry fiber was 180 MPa while that of the wet one was 158 MPa. Under wet condition, the tensile strength of the fiber was reduced by about 17% compared to the dry one. However; the wet fiber had higher strain than the dry one by about 26%. Under dry condition, the interfacial adhesion of the fiber was high compared to the wet, i.e. there was no pull out but debonding only. There was
a strong interlock between the fiber and the matrix [10]. Based on the case of betelnut fibers, dry coir fibers were therefore used in the manufacture of composites in this study as it can be argued that dry coir fiber would be stronger than the wet one. This would improve the suitability of the composites for manufacturing the body of tanks. Yousif et al. fabricated a new epoxy composite based on treated and untreated betelnut fibers and measured the tensile strength of the fibers using pull-out tests. The fibers were treated with NaOH solution. Before treating the fiber, a lot of foreign substances are trapped on the fiber surface. However the surface of the treated betelnut fiber is rougher than the untreated one and free from foreign substances. Nirmal et al. used treated betelnut fibers (in the mat form) as reinforcement in polyester composites and measured the tensile strength of the fibers using pull-out tests in dry/wet conditions. There was no pull out of fiber that took place during the test. Moreover, the strength was also the same as the single tensile result. This showed that the interfacial adhesion of the treated fiber under dry/wet conditions was very high, thereby preventing the pulling out process. Tanaka et al. carried out single fiber pull-out tests to investigate the influence of water absorption on the interfacial properties of aramid/epoxy composite. The fiber/matrix interfacial strength was severely decreased between 4 and 7 week immersion time in deionized water at 80 °C, and thereafter showed a plateau. This change with immersion time did not correspond with that of the water gain of the pull-out specimens, because the water gain did
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not reflect the one in the fiber/matrix interface. The interfacial strength of aramid/epoxy composite was decreased by 26% after 7 week immersion time in deionized water at 80 °C [13]. As a result of the degradation of the fiber/matrix interfacial strength, the pulled-out fiber surfaces of 7, 10 and 13 week wet specimen were smooth and were fractured by adhesive failure with interfacial crack and the fiber surface looked smooth. On the contrary, for dry and 4 week wet specimens the crack propagated in the matrix and much more matrix was found on the fiber, compared to the 7, 10 and 13 week wet ones. This difference of the fracture morphology corresponded to that of the interfacial strength. The fiber fracture load decreased by 37% for 7 week immersion time and showed almost constant thereafter [13]. In this study, duration of immersion of the samples was made 6 months and it can be argued that this might be over killed. In future studies, shorter immersion time could be used. Banholzer et al. proposed a numerical solution routine to provide a simple and straightforward analytical method to evaluate the prevailing bond characteristics of a composite by means of a bond stress versus slip relation s(s) using experimental data from pull-out tests. Time consuming and sometimes nonconvergent optimization procedures which had been used so far to determine pull-out strengths could be avoided. The proposed solution routine was applied and validated using experimental data from pull-out tests which were carried out at steel fiber/concrete systems. It was also shown that the underlying bond stress versus slip relation s(s) was a material parameter, since it was not dependent on geometric factors of fiber and matrix, for example fiber diameter and embedded length [14]. It can be argued that the authors need to do modelling to see whether the experimental results obtained in this study match those of simulation. Since 1960, attempts have been made to replace the steel storage tanks with reinforced plastic tanks [6,21]. Some of the storage tanks are exposed to different environments such as tap water, sea water, or chemical solutions. The most common reinforced plastic tank is the glass fiber reinforced polymer [6]. From the literature [6], the mechanical properties of such composite have been tested under seawater immersion conditions. In that work, it has been reported that interfacial adhesion of the glass fiber with different types of polymer is the main factor influencing the mechanical properties. In particular, 15–21% reduction in the strength of glass/polyester composites has been found after immersing the composites. The reduction in the strength seems to be due to the high reduction in the interlaminate shear strength, i.e. interfacial adhesion. In the current work, saltwater should very no effect on the interfacial adhesion of the coir fiber to the polyester matrix compared to other solutions. In other words, coir/polyester has high resistance to degradation (immersing process) compared to the glass fiber. 4. Conclusions As the interfacial adhesion between coir fibers and polyester is very high, the composite can be used in the design and manufac-
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ture the body of liquid storage tanks, particularly for storing water, salt water, diesel and engine oil. In order to improve the durability of the tanks manufactured. References [1] Nirmal U, Yousif BF, Rilling D, Breverna PV. Effect of betelnut fibres treatment and contact conditions on adhesive wear and frictional performance of polyester composites. Wear 2010;268:1354–70. [2] Arbelaiz A, Fernandez B, Ramos JA, Retegi A, Llano-Ponte R, Mondragon I. Mechanical properties of short flax fiber bundle/polypropylene composites: influence of matrix/fiber modification, fiber content, water uptake and recycling. Compos Sci Technol 2005;65:1582–92. [3] Sreekala MS, Thomas S. Effect of fiber surface modification on water-sorption characteristics of oil palm fibers. Compos Sci Technol 2003;63:861–9. [4] DiFrancis C, Ward T, Claus R. The single-fibre pull-out test. 1: Review and interpretation. Composites Part A 1996;27:597–612. [5] Hodzic A, Kim JK, Lowe AE, Stachurski ZH. The effects of water aging on the interphase region and interlaminar fracture toughness in polymer–glass composites. Compos Sci Technol 2004;64:2185–95. [6] Gellert EP, Turley DM. Seawater immersion ageing of glass–fiber reinforced polymer laminates for marine applications. Composites: Part A 1999;30:1259–65. [7] Tsotsis TK, Keller S, Lee K, Bardis J, Bish J. Aging of polymeric composite specimens for 5000 h at elevated pressure and temperature. Compos Sci Technol 2001;61:75–86. [8] Benavente J, Vazquez MI. Effect of age and chemical treatments on characteristic parameters for active and porous sublayers of polymeric composite membranes. J Colloid Interf Sci 2004;273:547–55. [9] Cervenka AJ, Young RJ, Kueseng K. Micromechanical phenomena during hygrothermal ageing of model composites investigated by Raman spectroscopy. Part II: Comparison of the behavior of PBO and M5 fibers compared with Twaron. Composites: Part A 2005;36:1020–6. [10] Yousif BF, Lau STW, McWilliam S. Polyester composite based on betelnut fiber for tribological applications. Tribol Int 2010;43:503–11. [11] Yousif BF, Nirmal U, Wong KJ. Three-body abrasion on wear and frictional performance of treated betelnut fibre reinforced epoxy (T-BFRE) composite. Mater Des 2010;31:4514–21. [12] Nirmal U, Yousif BF, Rilling D, Breverna PV. Effect of betelnut fibers treatment and contact conditions on adhesive wear and frictional performance of polyester composites. Wear 2010;268:1354–70. [13] Tanaka K, Minoshima K, Grela W, Komai K. Characterization of the aramid/ epoxy interfacial properties by means of pull-out test and influence of water absorption. Compos Sci Technol 2002;62:2169–77. [14] Banholzer B, Brameshuber W, Jung W. Analytical evaluation of pull-out tests the inverse problem. Cem Concr Compos 2006;28:564–71. [15] Yousef Payandeh, Fodil Meraghni, Etienne Patoor, André Eberhardt. Debonding initiation in a NiTi shape memory wire–epoxy matrix composite, Influence of martensitic transformation. Mater Des 2010;31(3):1077–84. [16] Khalid M, Ratnam CT, Chuah TG, Salmiaton Ali, Choong Thomas SY. Comparative study of polypropylene composites reinforced with oil palm empty fruit bunch fiber and oil palm derived cellulose. Mater Des 2008;29(1):173–8. _ [17] Onur Çoban, Mustafa Özgür Bora, Tamer Sinmazçelik, Ismail Cürgül, Volkan Günay. Fracture morphology and deformation characteristics of repeatedly impacted thermoplastic matrix composites. Mater Des 2009;30(3):628–34. [18] Hashmi SAR, Dwivedi UK, Chand Navin. Graphite modified cotton fibre reinforced polyester composites under sliding wear conditions. Wear 2007;262(11–12):1426–32. [19] Wong KJ, Zahi S, Low KO, Lim CC. Fracture characterisation of short bamboo fibre reinforced polyester composites. Mater Des 2010;31(9):4147–54. [20] Yang L, Thomason JL. Interface strength in glass fibre–polypropylene measured using the fibre pull-out and microbond methods. Compos Part A: Appl Sci Manuf 2010;41(9):1077–83. [21] McConnell Vicki P. Global underground: the state of composite storage tanks. Reinf Plast 2007;51(6):26–7. 29–31. [22] Chung Deborah DL. Carbon fiber composites. Butterworth-Heinemann: Reed Elsevier group; 1994.
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Suitability of using coir fiber/polymeric composite for the design of liquid storage tanks B.F. Yousif ⇑, H. Ku Centre of Excellence in Engineered Fiber Composites (CEEFC), Faculty of Engineering and Surveying, University of Southern Queensland, QLD 4350, Toowoomba, Australia
a r t i c l e
i n f o
Article history: Available online 17 March 2011 Keywords: Coir fiber Polyester Water Interfacial adhesion SEM and pull-out tests
a b s t r a c t Single fiber pull-out test is employed experimentally to model the interfacial adhesion characteristics of natural fibers with synthetic resin. The current study investigates the possibility of using coir fiber as reinforcements for polyester composites under aging process. The main application would be in designing tanks storage for different types of liquid. A single fiber pull out samples were soaked in seven different solutions (water, salt water, gasoline, diesel, break oil, engine oil, and power staring oil) for 6 months, and the pull-out tests were then carried out. Scanning electron microscopy (SEM) was used to examine the damage features on the samples. The results revealed that the highest amount of liquid absorbed was water, followed by salt water, which is due to the low viscosity of those liquids compared to other liquids. In spite of that, the highest interfacial adhesion property was found in samples soaked in salt water, which was about 120 MPa followed by water. SEM images showed that no pulling out process taking place during the test indicating high interfacial adhesion properties of coir fibers to the polyester. However, the differences in the interfacial adhesion properties are due to the deterioration in the fiber strength during the aging process. Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction Natural fibers are becoming an attractive alternative over synthetics fibers due to their advantages such as recyclability, biodegradability, renewability, low cost, light weight, high specific mechanical properties and low density [1–10]. Nowadays, applications of natural fibers reinforced polymeric composites can be found in housing construction material, industrial and automotive parts. From a mechanical point of view, natural fibers are good candidates for polymeric composites, i.e. low density, high strength, high flexural modulus, and high impact strength [2–7]. However, there is a limitation in the usage of natural fibers concerning their interfacial adhesion with matrix. Furthermore, it has been reported that interfacial adhesion of fiber to the matrix played the main role in controlling the mechanical properties of the composites [1,4,10– 14,19,20]. Untreated oil palm, jute, sugarcane, and banana fibers have very poor interfacial adhesion strength with polyester [1,18,19]. This poor interfacial adhesion is a result of foreign impurities/substances that prevents the matrix from bonding firmly with the fibers [1]. Single fiber or filament pull out technique has been used to model the failure of a composite material [15]. The interpretation of this model, however, varies between laboratories. Research, in the area of fiber pull out, has considered the fracture mechanics and shear stresses of fiber–matrix failure [15–17]. Var⇑ Corresponding author. E-mail addresses: [email protected] (B.F. Yousif), [email protected] (H. Ku). 0261-3069/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.matdes.2011.01.063
ious fiber/resin combinations and many sample configurations have been used in the single fiber models. ‘Fibers’ of interest embedded in matrices and subjected to tensile load [4]. Stress/ strain results indicate the interfacial adhesion characteristic of the fibers with the matrices. From the reported works, coir fibers showed very high interfacial adhesion properties under dry conditions. However, in real applications, products made of polymeric composite could be exposed to different environmental circumstances. For example, tanks could be filling in with water, salty water, gasoline, or other types of liquid. Understanding of the interaction and interfacial adhesion between the fibers and the matrix has not been explored yet. This motivates the current study on the interfacial adhesion characteristics of coir fiber with polyester matrix under different aging solutions. Furthermore, the potential application for such materials could be for vessels and tanks containing water, salty water, gasoline, diesel, brake oil, or power steering oil. Prepared single fiber pull out samples were immersed in different types of liquid for 6 months before being taken out for experiments. After this, samples were dried, tested, and then surface observations were conducted. 2. Materials and experimental details 2.1. Samples’ preparation Raw coconut fruit is obtained from a farm in Melaka state, Malaysia. The coconuts are taken during the dry session, where less
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rain occurs and moisture content for the coconuts is less. The outer layer shell or the mesocarp of the coconut is considered for the current work. The coconut gathered is from the Arecaceae family of palm, particularly cocus nucifera, Fig. 1a. The coconut fibers are firstly pulled out from the husk, Fig. 1b. Practically, husks were soaked in water to ease the extraction of the fibers. The extracted fibers were washed again to remove the embedded dirt between the fibers, Fig. 1c. Finally, the fibers were dried at ambient temperature (32 °C) for 48 h. Each single fiber was carefully picked and examined using an optical microscopy. The coir fibers having average diameter (320 lm) were carefully selected, Fig. 1d. The chemical composition of coir fiber is 45% lignin, 42% cellulose and 5% water. In the fabrication process of the single fiber pull out samples, aluminum mold (12.7 mm 12.7 mm 50 mm) was used. Two pieces of hard rubber (thickness of 3 mm) were cut and carefully fixed at both ends of the mold. One of the rubber pieces was punched in the center with a needle to insert the coir fiber. Before pouring the polymer mixture into the molds, the molds was first sprayed with release agent ‘Orelube Non Paintable Mold Release’ and was left to dry. The polyester resin, mixed with 2% hardener, was carefully poured in the mold. All the prepared samples after pouring the polyester were kept at the same room temperature (24 °C) for 24 h. Due to the difficulties in controlling the fiber position, a stainless steel needle was used to hold the fiber until the mixture get into jelly conditions. Moreover, to avoid any errors in the test which could occurs due to the fabrication process, several samples were fabricated and then examined by naked eyes. The samples having any defects, due to the fabrication process, were eliminated. The bonding between the fiber and the matrix could be chemical and/or mechanical bonding [22]. For the current work, the bonding area between the fiber and the matrix was examined. Fig. 2b and c shows the surface of the fiber interaction with the matrix. The high intimate contact between the fibers and the matrix indicates chemical bonding. Moreover, in Fig. 2c, it seems that the fiber is filled by polyester which indicates a mechanical bonding between the fiber and the matrix, i.e. interlock. In other words, both types of bonding took place between the fiber and the matrix.
(a)
(c)
Twenty-eight specimens were selected, divided equally and immersed into seven containers containing seven different solutions. The solutions used were engine oil (Petronas MACH 5 SAE 40), power steering oil (BS Power Steering Fluid), brake oil (Petronas Brake and Clutch Fluid DOT 3), diesel (Petronas), gasoline (Petronas), water, and salt water (25% salt). The specimens were left in the solutions for 6 months at atmospheric temperature and pressure [5–8]. From the supplier database, the viscosity of the solutions is provided in Table 1. After aging process (6 months), the samples were taken out from the containers and dried under the sun for 8 h. The weights of each of the samples were measured before and after the aging using an electric weighing scale (±0.1 mg). 2.2. Experimental details It seems to be no standard of measuring the interfacial adhesion of fiber with matrix. However, every laboratory, thus, has developed their own methods with essentially the same idea and different procedures [20]. The current work based on the most common technique in the literature [1,4,10–14,19,20]. The interfacial adhesion characteristics of the coir fiber with polyester matrix are investigated using single fiber pull out technique, Fig. 2. In the experiments, Universal Tensile Test Machine Q100 was used for the pull out process. In the test, the polyester end of the sample was rigidly fixed on the machine. The second end of the sample (fiber) was tapped and then gripped in the machine with a gauging length of 20 mm. The pulling rate was set to be 1 mm/min and continued until the failure. For each aging condition (solution), the test was repeated four times and the average associated with maximum and minimum values are determined. The error percentage of the collected data is presented in Fig. 3. 3. Results and discussions The results of the current work are summarized in four subsections as: liquid absorption, pull-out results, SEM observations, and discussions.
(b)
(d)
Fig. 1. The extraction of the coir fibers process.
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(a)
(c)
(b)
Fig. 2. Schematic illustration of single coconut fiber pull-out test sample and micrographs of the fiber/polyester bonding area.
Table 1 Average viscosity of selected solutions.
Liquid absorption Viscosity (Centistokes)
Water Salt water Gasoline Diesel Brake oil Engine oil SAE 30-50
0.80 0.82 0.95 5.50 12.00 135.00
3
Grams
Solutions
3.5 2.5 2 1.5 1 0.5 0
16 14
Fig. 4. Liquid absorption of the samples.
12 10
% 8 6 4 2 0
Brake oil
Diesel Power steering oil
Gasoline
Engine Saltwater Water oil
Fig. 3. Error percentage between the peak values of all the specimens.
3.1. Liquid absorption Fig. 4 shows the liquid absorption for each of the seven (28 in total) samples. It can be found that the highest amount of liquid absorbed is water, followed by salt water. These are followed by
brake oil, gasoline, diesel, engine oil and power steering oil. It is important to be noted that the absorption rate is influenced by the solution type. Besides, the physical appearance of the fiber is affected by the long time immersing in the solution. It is observed, by the naked eyes, that the fiber color has faded especially in the case of water and salt water aging. For other solution, the fiber becomes dark brownish and split of fiber can be observed. It can be argued that the liquid absorption was inversely proportional to the density of the liquid. In addition, it seems that the viscosity of the solution plays a role in influencing the absorption rate of the samples. In other words, the lower the viscosity is the higher the absorption rate (cf. Table 1 and Fig. 4). Such differences in the absorption rate associated with some interaction between the fiber and the solution could result in remarkable differences in the put out results.
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3.2. Pull-out tests Fig. 5 illustrates the maximum stresses of the specimens soaked in different types of liquid of the pull-out tests. The highest ones were samples soaked in salt water (120 MPa); this was followed by water, diesel, engine oil, brake oil, power steering oil and gasoline (75 MPa). It can be found that there is no correlation between the amounts of liquid absorbed by the samples to the maximum stresses of the samples (Fig. 4). However, water and salt water topped the lists. This implied that though water and salt water are likely to bring least damaged to the material of the tanks even they are absorbed most. It can be argued that not much chemical attack has been made to the material by water and salt water. On the other hand, some chemical damages might have been done on the material by other types of liquid. This will be furthermore discussion in the SEM observation section. Fig. 6a shows the graph for the specimens soaked in brake oil. In general, the graph shows varied trends of pulling out for all specimens. The peak values of the tensile stress are between 80 MPa and 130 MPa. This large difference in peak values resulted in the large standard deviation for specimens in brake oil as compared to the specimens in the other solutions. Out of the four specimens, one specimen had a broken fiber and the fibers of the remaining three specimens were pulled out completely. The broken fiber might be due to a weak point in the fiber. For the pulled-out fibers, the curves show a repeated fluctuating pattern until the fibers were completely pulled out. This may be due to the fluctuating grip between the rough surface of the coir fiber and the polymer during the pull out process. Fig. 6b illustrates the curves for the specimens soaked in diesel, which shows a consistent trend for every specimen. There was a small fluctuation for two of the samples before reaching the peak value which might be because of the fluctuating grip between the coir fiber and the polymer during pull out. The peak values of the tensile stress lay between 100 MPa and 120 MPa. The consistency in the trend resulted in the lowest standard deviation for the specimens soaked in diesel as compared to specimens soaked in the other solutions. Fig. 6c shows the curves for the specimens soaked in gasoline. The trend of these specimens was almost similar to that of the specimens soaked in diesel; three of the specimens had their stressed increased gradually until the peak value was reached and then dropped down, indicating the complete pull out. The remaining one specimen fluctuated around the peak value until the fiber got completely pulled out. The peak values of the tensile stress of the specimens soaked in gasoline lie between 65 MPa and 90 MPa. Fig. 6d shows the graph for the specimens soaked in engine oil. Two of the specimens showed a gradual increase in tensile stress until the fiber broke, which was indicated by the sudden drop in the tensile stress after peak value. The fibers of the remaining two specimens were completely pulled out. The peak values for
Maximum stress, MPa
140 120 100 80 60 40 20 0
Brake oil Power Diesel steering oil
Gasoline Engine Saltwater Water oil
Fig. 5. Maximum stresses of samples.
the tensile stress of the specimens soaked in engine oil lay between 98 MPa and 118 MPa. Fig. 6e shows the graph for the specimens in soaked power steering oil. The peak values of the four specimens were between 74 MPa and 96 MPa. Out of the four specimens, the fibers of the three were completely pulled out, and the remaining one specimen had a broken fiber after reaching the peak value. For the pulled out specimens, two of them showed a sudden drop in tensile stress after peak value and the other one specimen showed a fluctuating decrease in the tensile stress. This might be due to the fluctuating grip between the rough surface of the coir fiber and the polymer during the pull out process. Fig. 6f illustrates the graph for the specimens soaked in saltwater. The peak values of the tensile stress for all four samples lay between 108 MPa and 132 MPa. All of the fibers of the four specimens were pulled out completely. Two of the specimens showed a fluctuating decrease in the tensile stress, which might be due to the previously mentioned fluctuating grip of the coir fiber on the polymer. Fig. 6g shows the curves for the specimens soaked in tap water. From the graph, it can be found that all the fibers of the four specimens were completely pulled out, with a fluctuating decrease in tensile stress. All the specimens soaked in tap water reached a peak value of tensile stress between 100 MPa and 120 MPa. The above results could be due to two reasons. Either there is a chemical reaction between the fiber and the solution which led to the deterioration of the fibers or weakening in the fiber due to the absorption of the solution. From Table 1, the lower viscosity of solutions was in the water, i.e. high absorption of solution occurs when the samples immersed in water. However, the pull-out results indicated that the maximum interfacial adhesion property took place when the samples immersed in water compared to other solution. In other words, it can be concluded that amount of adsorption does not highly influences the interface adhesion property of the fibers with the matrix compared to the type of the solution. From the information given above, it can be found that the composites of coir fibers and polyester is generally suitable for manufacturing the body of tanks for storing different types of liquid except gasoline, power steering oil and brake oil as indicated by the lower pull-out stresses. This will be further confirmed in the SEM observation section.
3.3. Scanning Electron Microscope (SEM) observations The pull-out results can be explained with the assistance of Scanning Electron Microscope (SEM) micrographs [9]. It should be mentioned here that no SEM image analysis could be performed with specimens soaked in brake oil because severe chemical reaction occurred between the polyester and the brake oil. Therefore, further study is recommended. In Fig. 7a, the micrograph of the sample soaked in diesel shows that failure occurred due to fiber breakage of fiber rather than pull out of fiber. This indicated that the coir fibers have very high interfacial adhesion properties to the polyester despite being immersed in the diesel. This supported the results displayed in Fig. 6b. Fig. 7b, the micrograph of the sample soaked in gasoline, illustrates that failure was also due to the breakage in fiber. However, the fiber breakage occurred further than the bonding area; the fiber broke inside the polyester. This could be due to a weak point in the fiber, which broke when the pulling out process was going on. Fig. 7c, the micrograph of specimen soaked in engine oil, shows that there was debonding, but no pull out. The failure in pull out occurred because there was an empty gap between the polymer and the coir fiber. The empty gap resulted in low interfacial adhesion between the polyester and the coir fiber. The reason for this empty gap could be due to improper preparation of the specimen
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(a) Brake oil Brake oil 1 Brake oil 2 Brake oil 3 Brake oil 4
100
120 100
Stress, MPa
120
Stress, MPa
(b) Diesel
140
140
80 60
80 Diesel 1 Diesel 2 Diesel 3 Diesel 4
60
40
40
20
20 0
0 0
10
20
30
0
40
2
4
6
8
10
Displacement, mm
Displacement, mm
(d) Engine oil
(c) Gasoline 100
140
90 120
70
100
Stress, MPa
Stress, MPa
80 60 50 40 Gasoline 1 Gasoline 2 Gasoline 3 Gasoline 4
30 20
80
40 20
10 0
0
2
4
Engine oil 1 Engine oil 2 Engine oil 3 Engine oil 4
60
0
8
6
0
1
2
3
4
6
5
7
Displacement, mm
Displacement, mm
(e) Power steering oil
(f) Saltwater
8
9
10
11
100 90
140
80
120
Stress , MPa
Stress, MPa
70 60 50 40 30 20 10 0
0
2
4
100 80 60
Saltwater 1 Saltwater 2 Saltwater 3 Saltwater 4
40
Power steering oil 1 Power steering oil 2 Power steering oil 3 Power steering oil 4 8 6
20 0
12
10
0
5
10
Displacement, mm
15
20
25
30
35
40
Displacement, mm
(g) Water 140
Water 1 Water 2 Water 3 Water 4
Stress, MPa
120 100 80 60 40 20 0
0
5
10
15
20
25
30
35
40
Displacement, mm Fig. 6. Graphs for the pull-out test.
in the mold. The presence of bubbles during preparation could also have caused the empty gap.
Similar to the specimen in Fig. 7c, the micrograph of specimen soaked in power steering oil, Fig. 7d shows that there was debond-
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Fig. 7. Scanning Electron Microscope images of samples.
ing, but no pulls out. The failure in pull out occurred because there was an empty gap between the polymer and the coir fiber. The empty gap resulted in low interfacial adhesion between the polyester and the coir fiber. The reason for this empty gap could be because of improper preparation of the specimen in the mold. The presence of bubbles during preparation could also have caused the empty gap. Fig. 7e, the micrograph of sample soaked in salt water, illustrates that there was complete pull out of inner fiber. Although the fiber was pulled out, not the entire bundle was successfully pulled out. There were some remaining fibers stuck to the polyester. This indicated that the coir fibers had very high interfacial adhesion properties despite being soaked in the salt water. This supported the results in Fig. 7e. In Fig. 7f, the micrograph of specimen soaked in tap water shows that there was an incomplete pull out of inner fiber. Although the fiber was pulled out partially, there was still some fiber stuck to the polyester. This indicated that the coir fibers had very high interfacial adhesion properties despite being immersed in the tap water. This supported the results in Fig. 7f. Yousif et al. fabricated a polyester composite based on betelnut fibers and measured the tensile strength of the fibers in dry and wet conditions using pull-out tests. They found that the maximum stress for the dry fiber was 180 MPa while that of the wet one was 158 MPa. Under wet condition, the tensile strength of the fiber was reduced by about 17% compared to the dry one. However; the wet fiber had higher strain than the dry one by about 26%. Under dry condition, the interfacial adhesion of the fiber was high compared to the wet, i.e. there was no pull out but debonding only. There was
a strong interlock between the fiber and the matrix [10]. Based on the case of betelnut fibers, dry coir fibers were therefore used in the manufacture of composites in this study as it can be argued that dry coir fiber would be stronger than the wet one. This would improve the suitability of the composites for manufacturing the body of tanks. Yousif et al. fabricated a new epoxy composite based on treated and untreated betelnut fibers and measured the tensile strength of the fibers using pull-out tests. The fibers were treated with NaOH solution. Before treating the fiber, a lot of foreign substances are trapped on the fiber surface. However the surface of the treated betelnut fiber is rougher than the untreated one and free from foreign substances. Nirmal et al. used treated betelnut fibers (in the mat form) as reinforcement in polyester composites and measured the tensile strength of the fibers using pull-out tests in dry/wet conditions. There was no pull out of fiber that took place during the test. Moreover, the strength was also the same as the single tensile result. This showed that the interfacial adhesion of the treated fiber under dry/wet conditions was very high, thereby preventing the pulling out process. Tanaka et al. carried out single fiber pull-out tests to investigate the influence of water absorption on the interfacial properties of aramid/epoxy composite. The fiber/matrix interfacial strength was severely decreased between 4 and 7 week immersion time in deionized water at 80 °C, and thereafter showed a plateau. This change with immersion time did not correspond with that of the water gain of the pull-out specimens, because the water gain did
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not reflect the one in the fiber/matrix interface. The interfacial strength of aramid/epoxy composite was decreased by 26% after 7 week immersion time in deionized water at 80 °C [13]. As a result of the degradation of the fiber/matrix interfacial strength, the pulled-out fiber surfaces of 7, 10 and 13 week wet specimen were smooth and were fractured by adhesive failure with interfacial crack and the fiber surface looked smooth. On the contrary, for dry and 4 week wet specimens the crack propagated in the matrix and much more matrix was found on the fiber, compared to the 7, 10 and 13 week wet ones. This difference of the fracture morphology corresponded to that of the interfacial strength. The fiber fracture load decreased by 37% for 7 week immersion time and showed almost constant thereafter [13]. In this study, duration of immersion of the samples was made 6 months and it can be argued that this might be over killed. In future studies, shorter immersion time could be used. Banholzer et al. proposed a numerical solution routine to provide a simple and straightforward analytical method to evaluate the prevailing bond characteristics of a composite by means of a bond stress versus slip relation s(s) using experimental data from pull-out tests. Time consuming and sometimes nonconvergent optimization procedures which had been used so far to determine pull-out strengths could be avoided. The proposed solution routine was applied and validated using experimental data from pull-out tests which were carried out at steel fiber/concrete systems. It was also shown that the underlying bond stress versus slip relation s(s) was a material parameter, since it was not dependent on geometric factors of fiber and matrix, for example fiber diameter and embedded length [14]. It can be argued that the authors need to do modelling to see whether the experimental results obtained in this study match those of simulation. Since 1960, attempts have been made to replace the steel storage tanks with reinforced plastic tanks [6,21]. Some of the storage tanks are exposed to different environments such as tap water, sea water, or chemical solutions. The most common reinforced plastic tank is the glass fiber reinforced polymer [6]. From the literature [6], the mechanical properties of such composite have been tested under seawater immersion conditions. In that work, it has been reported that interfacial adhesion of the glass fiber with different types of polymer is the main factor influencing the mechanical properties. In particular, 15–21% reduction in the strength of glass/polyester composites has been found after immersing the composites. The reduction in the strength seems to be due to the high reduction in the interlaminate shear strength, i.e. interfacial adhesion. In the current work, saltwater should very no effect on the interfacial adhesion of the coir fiber to the polyester matrix compared to other solutions. In other words, coir/polyester has high resistance to degradation (immersing process) compared to the glass fiber. 4. Conclusions As the interfacial adhesion between coir fibers and polyester is very high, the composite can be used in the design and manufac-
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ture the body of liquid storage tanks, particularly for storing water, salt water, diesel and engine oil. In order to improve the durability of the tanks manufactured. References [1] Nirmal U, Yousif BF, Rilling D, Breverna PV. Effect of betelnut fibres treatment and contact conditions on adhesive wear and frictional performance of polyester composites. Wear 2010;268:1354–70. [2] Arbelaiz A, Fernandez B, Ramos JA, Retegi A, Llano-Ponte R, Mondragon I. Mechanical properties of short flax fiber bundle/polypropylene composites: influence of matrix/fiber modification, fiber content, water uptake and recycling. Compos Sci Technol 2005;65:1582–92. [3] Sreekala MS, Thomas S. Effect of fiber surface modification on water-sorption characteristics of oil palm fibers. Compos Sci Technol 2003;63:861–9. [4] DiFrancis C, Ward T, Claus R. The single-fibre pull-out test. 1: Review and interpretation. Composites Part A 1996;27:597–612. [5] Hodzic A, Kim JK, Lowe AE, Stachurski ZH. The effects of water aging on the interphase region and interlaminar fracture toughness in polymer–glass composites. Compos Sci Technol 2004;64:2185–95. [6] Gellert EP, Turley DM. Seawater immersion ageing of glass–fiber reinforced polymer laminates for marine applications. Composites: Part A 1999;30:1259–65. [7] Tsotsis TK, Keller S, Lee K, Bardis J, Bish J. Aging of polymeric composite specimens for 5000 h at elevated pressure and temperature. Compos Sci Technol 2001;61:75–86. [8] Benavente J, Vazquez MI. Effect of age and chemical treatments on characteristic parameters for active and porous sublayers of polymeric composite membranes. J Colloid Interf Sci 2004;273:547–55. [9] Cervenka AJ, Young RJ, Kueseng K. Micromechanical phenomena during hygrothermal ageing of model composites investigated by Raman spectroscopy. Part II: Comparison of the behavior of PBO and M5 fibers compared with Twaron. Composites: Part A 2005;36:1020–6. [10] Yousif BF, Lau STW, McWilliam S. Polyester composite based on betelnut fiber for tribological applications. Tribol Int 2010;43:503–11. [11] Yousif BF, Nirmal U, Wong KJ. Three-body abrasion on wear and frictional performance of treated betelnut fibre reinforced epoxy (T-BFRE) composite. Mater Des 2010;31:4514–21. [12] Nirmal U, Yousif BF, Rilling D, Breverna PV. Effect of betelnut fibers treatment and contact conditions on adhesive wear and frictional performance of polyester composites. Wear 2010;268:1354–70. [13] Tanaka K, Minoshima K, Grela W, Komai K. Characterization of the aramid/ epoxy interfacial properties by means of pull-out test and influence of water absorption. Compos Sci Technol 2002;62:2169–77. [14] Banholzer B, Brameshuber W, Jung W. Analytical evaluation of pull-out tests the inverse problem. Cem Concr Compos 2006;28:564–71. [15] Yousef Payandeh, Fodil Meraghni, Etienne Patoor, André Eberhardt. Debonding initiation in a NiTi shape memory wire–epoxy matrix composite, Influence of martensitic transformation. Mater Des 2010;31(3):1077–84. [16] Khalid M, Ratnam CT, Chuah TG, Salmiaton Ali, Choong Thomas SY. Comparative study of polypropylene composites reinforced with oil palm empty fruit bunch fiber and oil palm derived cellulose. Mater Des 2008;29(1):173–8. _ [17] Onur Çoban, Mustafa Özgür Bora, Tamer Sinmazçelik, Ismail Cürgül, Volkan Günay. Fracture morphology and deformation characteristics of repeatedly impacted thermoplastic matrix composites. Mater Des 2009;30(3):628–34. [18] Hashmi SAR, Dwivedi UK, Chand Navin. Graphite modified cotton fibre reinforced polyester composites under sliding wear conditions. Wear 2007;262(11–12):1426–32. [19] Wong KJ, Zahi S, Low KO, Lim CC. Fracture characterisation of short bamboo fibre reinforced polyester composites. Mater Des 2010;31(9):4147–54. [20] Yang L, Thomason JL. Interface strength in glass fibre–polypropylene measured using the fibre pull-out and microbond methods. Compos Part A: Appl Sci Manuf 2010;41(9):1077–83. [21] McConnell Vicki P. Global underground: the state of composite storage tanks. Reinf Plast 2007;51(6):26–7. 29–31. [22] Chung Deborah DL. Carbon fiber composites. Butterworth-Heinemann: Reed Elsevier group; 1994.