Formability of Metal Foam Cored Sandwich Steel Sheets

Available online at www.sciencedirect.com

ScienceDirect Materials Today: Proceedings 5 (2018) 25255–25264

www.materialstoday.com/proceedings

IConAMMA_2017

Formability of Metal Foam Cored Sandwich Steel Sheets Arjun Ramesh*1, Samanyu Sathian and V. Satheeshkumar 1

Department of Mechanical Engineering,Amrita School of Engineering,Coimbatore, Amrita Vishwa Vidyapeetham,Amrita University, India, 641112

Abstract

The sandwich sheets categorized under tailor made blanks are widely used in the aircrafts, automobiles, and ship structures. Metal foam used in the sandwich sheets influences the mechanical properties of sandwich sheets. Since the sandwich sheets are used as formed parts in most of the manufacturing applications, it is curious to study on the formability of sandwich sheets fabricated with the influence of metal foam properties and choosing suitable properties. The main objective of the present work is to investigate the influence of metal foam properties on the formability of sandwich steel sheets. Comparison is drawn between bonded sheets, foam cored bonded sheets and foam cored reinforced bonded sheets. The tensile test was carried to evaluate the results like % elongation, strain hardening exponent (n), and limit strain in the base material constituting sandwich sheets for basic characterization of formability of sandwich sheets. The results show that there is a moderate improvement in overall formability of sandwich sheets. This is due to the improved ductility of adhesive which is rich in formulation of hardener reinforced with high ductile copper foam in the presence of interface bonding between base materials and reinforced adhesive layer. It is concluded that low ductile adhesive layer reinforced with high ductile metal foam material improves the formability of sandwich sheets. © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Advances in Materials and Manufacturing Applications [IConAMMA 2017]. Keywords:Adhesive bonded sheets, Foam cored, Reinforced,Epoxy,Foam *

corresponding author Tel:+919656415658 E-mail address: [email protected]

2214-7853© 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Advances in Materials and Manufacturing Applications [IConAMMA 2017].

25256

Arjun Ramesh et al., / Materials Today: Proceedings 5 (2018) 25255–25264

Nomenclature DD deep drawing quality SS stainless steel 1. Introduction In current scenario there is increased demand of technology that meets requirements of light weighting, better surface attributes, mechanical and functional properties [1]. Adhesive bonding unlike other joining methods do not involve conditions of stress concentration and high temperature. It provides better joint efficiency, economic viability and dissimilar material joining [1]. Adhesive bonding helps in manufacturing lighter and cost effective aircraft components without compromising the structural strength and performance. The intermediate adhesive layer property improves the galvanic corrosion resistance and vibration damping thereby increasing the lifespan of the component [2]. Dissimilar materials with a low melting point can be effectively joined with the use of adhesive bonding. Sandwich sheet come under category of tailor made blanks. Metal foams can be defined as a two phase compound of a solid and gas with physical and mechanical properties which are very interesting. It possesses properties such as very low density, good rigidity, energy absorption characteristics, vibration damping [3]. Metal foams are made by either a direct foaming process or using a precursor. The produced metallic foam have inherent property of the parent metal from which they are made. The structural property of a typical foam is represented by its pore size, number intersection of pores and the thickness of the foam material[3]. Metallic foam can be categorized into twonamely open cell metallic foam and closed cell metallic foam Open cell foam is characterized by their high porosity [4]. The properties of metallic foam are dependent on the material of which it is made and structure of the pores. Whenever there is a structural application, the usage of metal foam is limited. That is where the foam cored sandwich sheets come into picture. In sandwich panels the foam is glued to cover sheets with adhesive. The limitation of using metallic foam in application is that whichever structure that it is used for, is made by foaming process. Further steps of shaping are limited. Therefore studying how the formability of foam cored sandwich panels depends on foam properties is curious case of study. Foam cored sandwich structure comprises of a low weight foam core in between with two face sheets having good strength and stiffness. Foam cored sandwich steel panels comprises of very high porous metallic foam between two steel face sheet Bare foam has poor tensile properties [4]. Contorno [5] demonstrated a simple forming process for manufacturing of foam cored sandwich panels. The formability was found to be dependent on the thickness of foam used as the core. Urso[6] studied the formability of foam cored sheets manufactured by different methods. Out of all the formability was better when it the foam core was glued to skin sheets. The foam is bonded to the face sheets by a suitable adhesive there by giving combination of high strength and elongation. Santos [7] observed that the yielding of the global structure is pivotal in the formability of the composite sandwich panel. Yielding was observed wherever the pore had larger dimensions. Satheeshkumar and Ganesh Narayanan investigated how adhesive properties influence formability of dissimilar steel sheets [8]. They were able to demonstrate an increased formability which can be attributed to a increased hardener/resin ratio. . The value of strain hardening exponent increases with increase in hardener/epoxy ratio as demonstrated [8] .The formability of less formable material Deep drawing quality steel can be improved using a high formable material like SS316L and improved hardener/resin ratio. The formability of adhesive bonded thin sheets reinforced with metallic wires was investigated by Satheeshkumar and Ganesh Narayanan. The results showed significant improvement in ductility, limit strains and draw ability [9].. The tensile testing results reported that a considerable increase in bond strength compared with non-reinforced adhesive. Ravi Kant and Narayanan [10] have investigated the role of adhesive thickness bond width on formability of adhesive bonded dissimilar sheets. Higher bonding width improved the total elongation of the bonded sheets and reduced extension at failure There are some evidences in the literature that the metal foam used in the sandwich sheets influences the mechanical properties of sandwich sheets. Since the sandwich sheets are used as formed parts in most of the manufacturing applications, it is curious to study on the formability of sandwich sheets fabricated with the influence of metal foam properties and choosing suitable properties. The main objective of the present work is to investigate

Arjun Ramesh et al.., / Materials Today: Proceedings 5 (2018) 25255–25264

25257

the influence of metal foam properties on the formability of sandwich steel sheets. Comparison is drawn between bonded sheets, foam cored bonded sheets and foam cored reinforced bonded sheets. The tensile test is carried out. The results like load- extension, stress-strain behavior, strain hardening exponent and limit strains in the base materials are monitored in the tensile test. 2. Methodology 2.1Experimental materials and mechanical properties A pair of cold rolled DDQ (DDQ CR2) steel sheets and SS202 sheets is used as outer layer for adhesive bonding. The base material sheets with 0.6mm thickness are cut based on ASTM E646-98 standard with the help of water jet cutting. Around 48 samples are cut from different locations including rolling direction to ensure the repeatability of the data.The foam used is open celled copper foam of thickness 2mm.The open cell copper foam was cut by ASTME646-98. The base material sheets are washed in the soap solution and final cleaning is done with acetone. After drying the samples circular grids are imprinted on the gauge length area of DDQ and SS202 in order to evaluate the limit strains. About 60 circles are measured using profile projector and an average diameter of 60 circles 2.421±0.05mm is found .SEM EDAX analysis was done on copper foam to understand about its purity with regards to copper and determine chemical composition shown in figure1.The chemical compositions of cold rolled DDQ steel, sheet stainless steel 202 and copper foam are tabulated in Table 1.The dimensions of the tensile samples used for testing (ASTM E646-98) are shown in figure 1(a). The thickness of base materials is 0.6 mm each. The tensile tests are carried out at an average room temperature of 25-degree Celsius on Tinius Olsen H25KT (capacity =25KN) with cross head speed of 1mm/min.The load extension plots are recorded with the help of QMAT Professional software. Four samples from each base material are tested to ensure the repeatability of the plot. Out of four samples if more than one sample shows dissimilarity one more sample is tested to ensure repeatability in the result. Figure 3(a), (b) represents the load extension plot of deep drawing quality CR2 , SS202 and copper foam respectively. The deep drawing quality steel showed a most repeatable plot with an elongation of 31±1%.The stainless steel sheet (SS202) showed a higher elongation value of 37±1% compared to deep drawing quality steel. The elongation of copper foam was 10±0.3%.The engineering stress-stain curves are plotted from load-extension curve and mechanical properties such as total elongation, ultimate tensile strength ,and yield strength are extracted. To assess the values of strain hardening exponent (n) and strength coefficient (K) based on Holliman’s law (σ=Kεn) true stress-strain curves are plotted from engineering stress-strain plots. The mechanical properties are tabulated in table 2. Table 1 Chemical composition of base materials . materials C% Si% Mn%

(a)

S%

O%

Al%

P%

Cr%

N%

Ni%

Cu%

Fe%

DDQ

0.1

0.12

0.600

0.035

-

-

0.040

-

-

-

-

remaining

SS202

≤0.15

≤1

7.50-10

≤0.030

-

-

≤0.060

17-19

≤0.25

4-6

-

68

Cu Foam

-

-

-

1.25

9.21

0.64

-

-

-

-

-

88.54

(a)

Figure 1 a) tensile samples of base materials

(b)

(b)

Figure 1b) SEM EDAX of Cu foam

25258

Arjun Ramesh et al., / Materials Today: Proceedings 5 (2018) 25255–25264

Figure 2(a)

Figure 2(b)

Figure 2(c) Figure 2(d) Figure 2 Dimensions of tensile testing specimen (a) ASTM E646-98 specimen (b)ASTM D638-1 epoxy testing specimen (C) bonded sheets (d) foam cored with and without adhesive reinforcement(2mm foam thickness filled with adhesive) Table 2 Mechanical properties of base materials material

Yield strength

Ultimate tensile

(MPa)

strain

Strength

elongation(%) in 82-

hardening

mm gauge length

coefficient(n)

coefficient(k)

DDQ steel

185±5

290±5

31±1

0.226±0.02

504±10

SS202

275±5

540±5

37±1

0.346±0.02

1721±10

Cu foam

8.3±0.15

13.25±1.5

10.6±0.3

-

-

14

7000

SS202

12

5000

DDQ

4000

10

DDQ single sheet SS202 single sheet

3000

Load in N

6000

Load in N

Total

strength(MPa)

8 cu foam 6

2000

4

1000

2

0

0 0

5

10

15

20

25

30

35

0

2

Extension in mm

4

6

8

10

Extension in mm

Figure 3 Load Vs Extension (a) DDQ and SS202 single sheet (b)Copper foam

2.2 Evaluation of tensile properties of the epoxy-based adhesive system The adhesive tensile samples are prepared according to ASTM D638-1 figure2(b) and tensile tests are carried out in same Tinius Olsen H25KT tensile testing machine. Epoxy based adhesive system with hardener resin ratio of 1:1 is preferred for preparing tensile samples. Satheeshkumar and Ganesh Narayanan [8] investigated the relationship between hardener resin ratio and formability of adhesive bonded steel sheets. The results show that increasing the hardener resin ratio improves the formability of the adhesive bonded sheet. This study suggested an optimum hardener resin ratio of 1:1 for maximum elongation of the bonded sheet. Adhesive samples are made with the help of a fabricated mold setup. The ASTM D638-1 samples are cut out from a 6mmm thick steel plate the left over steel plate is used for preparing the samples. Hardener and resin of epoxy (H/R 1:1) adhesive were poured into a container

Arjun Ramesh et al.., / Materials Today: Proceedings 5 (2018) 25255–25264

25259

and mixed thoroughly until a homogenous mixture is formed. A thin film of grease or oil is coated on the walls of the mold before pouring the mixture to prevent adhesion between wall and the specimen. The extra adhesive mixture is wiped out with a steel ruler. After 24 hours setting time at room temperature, the specimens are taken out and ensured dimensional accuracy. The thickness of the samples is measured and found to be 5.0±0.05mm.The loadextension curves are plotted by testing the samples in Tinius Olsen H25KT tensile testing machine with a cross head speed of 1mm/min at room temperature. The engineering stress-strain curves are plotted from the load-extension curve and mechanical properties of the adhesive samples are evaluated. The repeatability is maintained by testing a sufficient number of samples. The figure 4 shows the load extension plot of ASTM D638-1 adhesive sample. 1600 1400

Load in N

1200 1000 800 600 EPOXY with H/R ratio 1:1

400 200 0 0

1

2

3

4

5

6

7

Extension in mm

Figure 4 Load Vs Extension for epoxy with H/R=1:1

2.3 Tensile testing of bonded sheets, bonded sheets with foam core non reinforced and reinforced with epoxy-based adhesive system To understand how the formability of a foam cored sandwich sheet is dependent on metal foam a set of 3 samples in each case were prepared that is bonded sheets, bonded sheets with foam core non reinforced with adhesive and bonded sheets with foam core reinforced with adhesive. In case of bonded sheets with foam core non reinforced a adhesive thickness of 0.9 mm was maintained above and below the foam core with help of shim sheets. Inbonded sheets with foam core reinforced with adhesive a similar thickness was maintained but the pores was completely reinforced with adhesive.Prior to fabrication of samplesthe base material sheets are washed in the soap solution and final cleaning is done with acetone.A homogenous epoxy adhesive is prepared with 1:1 hardener resin ratio. Uniform thickness of the adhesive is maintained in between the base materials with the help of shim sheets. In all the different specimens prepared for comparison the total thickness was 5.0±0.05mm.Circular grids are imprinted on the gauge length area in order to evaluate the limit strains.Tensile tests are carried out in same Tinius Olsen H25KT tensile testing machine with a cross head speed of 1mm/min at room. The dimensions of the specimens are shown in fig 2(d) and 2(e). (a)

(b)

(c)

(d)

(e) Foam core non reinf orced

(f) Foam core reinfo rced

Figure 5 a) mold for bonded specimen b) bonded sheets(ABB) c) bonded sheets with foam core non reinforced d) bonded sheets foam core reinforced (ABB) e) bonded sheets foam core non reinforced f)bonded sheets foam core reinforced (ABBERF)

25260

Arjun Ramesh et al., / Materials Today: Proceedings 5 (2018) 25255–25264

3. Results and Discussion 3.1 Influence of foam in adhesive bonded sheets Failure pattern analysis of bonded sheets with foam cored non reinforced and reinforced.The failure pattern of different layers of the adhesive bonded sheet is analyzed. Failure of each layer is monitored visually during tensile testing and from load extension data. (c)

(b)

(a)

Adhesive failure

Multiple location Adhesive failure back to back

Adhesive failure at one location

Figure 6 (a) failure of the adhesive (middle portion) (b) adhesive failure in foam cored non reinforced(c) adhesive failure in foam cored reinforced

Failure of intermediate adhesive layer In tensile testing the failure initially occurs in the adhesive layer. This is owing to the less ductility. Generally in bonded sheets after adhesive failure the relative motion occurs between base materials during deformation. But in bonded sheets with foam cored reinforced even after failure of adhesive layer, bonding was still visible between the base materials. A trend can be witnessed that reinforced foam reduces delamination. In foam cored reinforced bonded sheets reinforced first failure occurred only at one location. The second failure was when the DDQ failure took place. But it was observed in 6(b) that failure occurred at multiple locations back to back after first failure. It can be said that though the ductility of adhesive layer improved, the improvement in ductility of the adhesive layer is more when the pores are reinforced with adhesive than a foam core that is not filled with adhesive. Failure of DDQ steel sheets After the failure of the intermediate adhesive layer, the tensile load is shared by base materials alone. Less formable deep drawing quality steel sheet fails after adhesive failure. The failure of both adhesive layer and DDQ sheet are observed on the gauge length region. Failure of DDQ in foam cored bonded sheets with reinforcement was closer to the region where the reinforced foam core failed. Failure of SS202 sheet Due to high formability of the stain less steel base material the failure of SS202 happens at last. The same failure pattern is observed in all adhesive bonded specimens.

Arjun Ramesh et al.., / Materials Today: Proceedings 5 (2018) 25255–25264

25261

3.2Comparison between bonded sheets, without foam core reinforcement and with foam core reinforcement 10000

.

9000

ABBERF

8000

Load in N

7000 6000 5000

ABBF

4000

ABB

ABB

ABBF

3000

Global behaviour of bonded sheets

2000

forming behaviour of DDQ+SS202

1000

ABBERF forming behaviour of SS202

0 0

5

10

15

20

25

30

35

40

45

Extension in mm

Figure 7 Load Vs Extension for bonded samples DDQ: deep drawing quality steel, SS: Stainless steel, ABB: adhesive bonded blanks, ABBF: adhesive bonded blanks foam core non reinforced, ABBERF- adhesive bonded blanks foam core reinforced.

From load extension data it can be witnessed that the bonded sheets with foam core non reinforced (ABBF) though exhibited an increase in ductility of adhesive layer it does no good to improvement in ductility of DDQ steel. The failure also occurred at multiple locations. But in case of bonded sheets with foam core reinforced (ABBERF), there is improvement in all failure regions. The foam increases the ductility of adhesive layer and also that of DDQ. It was clearly evident from load extension behaviour bonded sheets with foam core reinforced with adhesive was showing added extension during global behaviour which is absent bonded sheets foam cored without reinforcement. Table 3 Comparison of total extension with respect to bonded sheets Bonded sheets ABBF

% increase in total extension till DDQ failure -8.5

% increase in total extension till SS202 failure -1

ABBERF

3.79

22

% total extension = (extension of bonded sheets with reinforced foam core/non reinforced till failure of DDQ/SS202- extension of bonded sheets till failure of DDQ/SS202)/ (extension of bonded sheets till failure of DDQ/SS202). Table 4 Total extension with respect to single sheets Bonded sheets

% increase in total extension till

% increase in total extension till

ABB

DDQ single sheet failure 6.4

SS202 single sheet failure 11

ABBF

-2.08

10

10.3

35 ABBERF % total extension = (extension of bonded sheets with reinforced foam core/non reinforced/epoxy bonded sheets till failure of DDQ/SS202/extension till failure of DDQ/SS202 single sheet)/( extension of till failure of DDQ/SS202 single sheet), DDQ: deep drawing quality steel, SS: Stainless steel, ABB: adhesive bonded blanks, ABBF: adhesive bonded blanks foam core non reinforced, ABBERF- adhesive bonded blanks foam core reinforced

25262

Arjun Ramesh et al., / Materials Today: Proceedings 5 (2018) 25255–25264

From the above table 4 it can be concluded that the foam enriched with adhesive contributes to more ductility to DDQ. There is a increase of about 4% in total extension in DDQ in bonded sheet whereas in bonded sheets with foam core non reinforced there is no improvement. Foam enhances ductility of adhesive layer but the ductility of DDQ only when its pores are enriched with adhesive. Higher bonding width improved the total elongation of the bonded sheets[10] more in foam enriched with adhesive (ABBERF) than foam core non reinforced (ABBF). Table 5 Comparison of % increase in total elongation results of DDQ and SS202 in bonded sheets with respect to single sheets Bonded sheets

%Increase in total elongation in 82mm

%Increase in total elongation in 82mm

gauge length in DDQ steel

gauge length in SS202

ABB

6.26

12.9

ABBF

-2.80

11.5

ABBERF

10.30

37.15

% total elongation = (elongation of bonded sheets with reinforced foam core/non reinforced/epoxy bonded sheets till failure of DDQ/SS202)elongation till failure of DDQ/SS202 single sheet)/( elongation of till failure of DDQ/SS202 single sheet) DDQ: deep drawing quality steel, SS: Stainless steel, ABB: adhesive bonded blanks, ABBF: adhesive bonded blanks foam core non reinforced, ABBERF- adhesive bonded blanks foam core reinforced

The % total elongation when compared to single sheet is more for adhesive bonded blanks foam core reinforced (ABBERF) than other two. 140

Failure of adhesive layer

Failure of DDQ

Engineering stress in MPa

120 100 Failure of SS202

80

ABBF ABBERF

60

ABBERF

ABB

40

ABB ABBF

20

Region 1

Region 3

Region 2

0 0

0.1

0.2

0.3

0.4

0.5

0.6

Engineering strain

Figure 8 Engineering stress- strain curve DDQ: deep drawing quality steel, SS: Stainless steel, ABB: adhesive bonded blanks, ABBF: adhesive bonded blanks foam core non reinforced, ABBERF- adhesive bonded blanks foam core reinforced

Region 1 represents the global forming behavior of adhesive bonded sheets. In the case of bonded sheets (ABB) without foam it is adhesive layer along with DDQ steel and SS202, in bonded sheets foam cored (ABBF)it is the foam -adhesive ,along with DDQ and SS202 and in bonded sheets in bonded sheets foam cored reinforced(ABBERF) foam -adhesive ,along with DDQ and SS202. Region 2 represents forming behavior of DDQ

Arjun Ramesh et al.., / Materials Today: Proceedings 5 (2018) 25255–25264

25263

steel sheet and SS202 in bonded sheets(ABB), bonded sheets with (ABBERF)and without reinforcement(ABBF). Region 3 represents the forming behavior of SS202 in bonded sheets (ABB), bonded with (ABBERF) and without foam cored reinforced (ABBF). Strain hardening exponent (n) determines the value of forming behavior [. Strain hardening exponent values are determined from and tabulated below in table 6 for different regions. Table 6 Strain hardening exponent Material

Region I

Region II

Region III

Bonded sheets

0.261

0.368

0.554

Bonded sheets with foam non reinforced

0.271

0.214

0.512

Bonded sheets with foam reinforced

0.297

0.377

0.594

In all three regions of bonded sheet foam cored with adhesive reinforcement (ABBERF) there is a increase in n value. The high ductile foam increases the formability in all regions. On comparison of ABBF with ABBERF with regards to n value in second region it can be said that the foam when enriched with adhesive not only increases formability of adhesive layer but also the less formable DDQ. 3.3Influence of metal foam on limit strain 0.7

True major strain

0.6 0.5 0.4 0.3 DDQ1 DDQ3 SS202-1 SS202-3

DDQ2 DDQ4 SS202-2 SS202-4

0.2 0.1 0

-0.5

-0.4

-0.3

-0.2

-0.1

0

Figure 9 Comparison of limit strain[DDQ-1(DDQ single sheet),DDQ-2(bonded sheets),DDQ3(DDQ in bonded sheets foam non reinforced),DDQ-4 (DDQ in bonded sheets foam reinforced ),SS202-1( SS202 single sheet ),SS202-2( SS202 in bonded sheet) ,SS202-3(SS202 bonded sheets foam non reinforced),SS202-4(SS202 bonded sheets foam reinforced)

True minor strain

In order to arrive at a reason for improvement in limit strain observed in bonded sheets with foam core compared to bonded sheets with no foam and single sheet, it can be related with the n values. The global formable behavior of DDQ steel sheet shows value of 0.297 in region 1 in bonded sheets with foam core reinforced, whereas it is 0.261 in region 1 in bonded sheets without foam and 0.271 is foam core non reinforced. In DDQ steel single sheet it is 0.224. This indicates that DDQ in foam cored reinforced bonded sheets has deformed more plastically. Likewise in region 2 in foam cored bonded sheets n value of DDQ is greater on comparison with that of DDQ in region 2 on bonded sheets without foam and DDQ single sheet. The plastic deformation caused by the global behavior of foam cored bonded sheets has led to an increase in the limit strain in base materials. This is due to the high ductile copper foam.. The improvement in limit strain value of DDQ is mainly due to the foam reinforced with epoxy. The standard deviation true major strain in SS202 in three cases is0.0073, 0.0036 and 0.012. In DDQ steel it is 0.0083, 0.0034, and 0.0071. The deviation was calculated to avoid error in manual measurement of limit strains 4. Conclusions The following conclusions are drawn from the study.  The elongation of sandwich sheets fabricated with copper foam reinforced adhesive increases as compared to unreinforced adhesive bonded sheets.

25264

  

Arjun Ramesh et al., / Materials Today: Proceedings 5 (2018) 25255–25264

There is a significant improvement in ductility of less formable DDQ single sheet which is due to foam reinforced with epoxy and also the more formable SS202 The limit strains of base materials constituting sandwich sheets with copper foam reinforced adhesive increase as compared to unreinforced adhesive bonded sheets. The overall formability of sandwich sheets improves with adhesive layer reinforced by high ductile metal foam material.

References [1] Martin Hornung and Michael Hajj, structural bonding for lightweight construction , Materials Science Forum Vols.618-619(2009) pp 495681-7764-495-5(2003) [2] ShantanuBhowmik, Benedictus, R., and Dan, Y Adhesive Bonding Technology, in Handbook of Manufacturing Engineering and Technology, Springer, 2014, pp. 765–784 [3] J.Banhart,Aluminum Foam for lighter vehicles, International Journal of Vehicle Design 37,114-125(2005) [4]S.Shima and M.Oyane, Plasticity Theory for Porous Metals, International Journal of MechanicalSciences, Vol 18 pp 285-991(1976) [5]D. Contorno , L. Filice , L. Fratini ,F. Micar, Forming of Aluminum sandwich panels, Journal Materials Processing Technology 177 (2006) [6]Gianluca D Urso, Giancarlo Maccarini, Formability of aluminum foam sandwich panels,International Journal Material Forum 5:243257(2012) [7]A.Santos,H.Mata,A.AFernandes, Study of Formability of Sandwich steel sheels with metal foam core,Key Engineering Materials Vols 554557(2013) [8]V.Satheeshkumar and Ganesh Narayanan R, Prediction of formability of adhesive bonded steel sheets, archives of civil and mechanical engineering 30 – 41 (2015) [9]V.Satheeshkumar and Ganesh Narayanan R, Forming performance of adhesive bonded steel sheets reinforced with metallic wires, 59:883900,weld world(2015) [10] Ravi Kant and Ganesh Narayanan.(2012), In-Plane Testing Behavior of Adhesive-Bonded Steel Sheets: Influence of Sheet Surface Roughness, Adhesive Thickness, and Bonding Width, Journal of Testing and Evaluation, Vol. 40 (2), pp. 97-106.