Prediction of in-plane stiffness of multi-material 3D printed laminate parts fabricated by FDM process using CLT and its mechanical behaviour under tensile load

Journal Pre-proof Prediction of in-plane stiffness of multi-material 3D printed laminate parts fabricated by FDM process using CLT and its mechanical behaviour under tensile load Pradeep Kumar Mishra, Senthil P

PII:

S2352-4928(20)30228-2

DOI:

https://doi.org/10.1016/j.mtcomm.2020.100955

Reference:

MTCOMM 100955

To appear in:

Materials Today Communications

Received Date:

5 July 2019

Revised Date:

9 December 2019

Accepted Date:

21 January 2020

Please cite this article as: Kumar Mishra P, P S, Prediction of in-plane stiffness of multi-material 3D printed laminate parts fabricated by FDM process using CLT and its mechanical behaviour under tensile load, Materials Today Communications (2020), doi: https://doi.org/10.1016/j.mtcomm.2020.100955

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Prediction of in-plane stiffness of multi-material 3D printed laminate parts fabricated by FDM process using CLT and its mechanical behaviour under tensile load

Pradeep Kumar Mishra, Senthil P*

Department of Production Engineering, National Institute of Technology, Tiruchirappalli, 620015, India

Corresponding Author: [email protected]

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Graphical abstract

Abstract

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The use of fused deposition modeling (FDM) process in the making of the multi-material 3D printed part is adding a new dimension in the area of additive manufacturing technology. This

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paper highlights the procedures to print bi-material laminate parts with different raster orientation by applying FDM technique and describe its mechanical behaviour using classical laminate theory (CLT). For excellent thermal diffusion and substantial functionalities, polylactic acid (PLA) and polylactic acid carbon black (PLA CB) were selected as feedstock materials for printing bi-material structure. The theoretical in-plane stiffness of 3D printed bimaterial laminate parts was calculated by using the philosophy of CLT, and the result was validated against experimental value. Fourier-transform infrared spectroscopy (FTIR) study on feedstock filament materials and 3D printed samples ascertained the cause for molecular

degradation in printed parts. Furthermore, at different raster orientation, the average tensile properties like tensile stiffness, ultimate tensile strength(UTS) and breaking strain of 3D printed bi-material laminate parts were investigated and compared with mono-material laminate models. Fractography analysis of failure surfaces of bi-material laminates was done by scanning electron microscope(SEM) to explore the nature of failure under tensile loading.

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Abbreviation

additive manufacturing

FDM

fused deposition modeling

3D

three-dimensional

ABS

acrylonitrile–butadiene styrene

PC

polycarbonate

PLA

polylactic acid

CB

carbon black

CLT

classical laminate theory

FTIR

fourier-transform infrared spectroscopy

DSC

differential scanning calorimetry

UTS

ultimate tensile strength

SEM

scanning electron microscope

STL

standard triangle language

ASTM

american society for testing and materials

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AM

Keywords: Additive manufacturing; Multi-material printing; Fused Deposition Modelling; Classical Laminate Theory

1. Introduction Additive manufacturing(AM) process presents a cutting edge technology in the area of prototyping and product development process in the current manufacturing trend. To meet the objectives of industry 4.0 revolution, both in the academic and industrial unit, the demand for AM is growing exponentially to utilize the advantages of the process. Using additive manufacturing process, it is now possible to build the geometry of the complicated structure, which was quite tedious in the subtractive manufacturing process. The AM defines as the process in which the 3D CAD model is made into the part by depositing material layer by

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layer[1]. Polymers, metals, alloys, and ceramics are used as feedstock material for the AM process and met design criteria successfully[2]. Among all types of the AM process, FDM

weighs more in terms of applications and functionality drew the attention of researchers and manufacturers. In the FDM process, the raw material feed to liquefier in the form of wire where it melts partially and then deposited over the build- plate through the help of a

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nozzle[3]. The common feedstock materials for fused deposition process are acrylonitrile butadiene styrene(ABS), PLA, polycarbonate(PC) and many more. Among them, PLA is

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hugely used in the research community, which carries excellent biodegradability quality and possesses good biocompatibility[4]. Ceramics like lead-zirconate-titanate, lead-magnesium-

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niobate ceramic, and alumina used in fused deposition ceramic process to fabricate net shape electro-mechanical components, photonic bandgap structure and transducers[5].

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The structural application of the FDM process is evolving rapidly in the area of automobile, aerospace, robotics because of its capabilities in making the complicated and versatile parts [6][7]. Aerospace manufacturing companies are utilizing topology optimization technique to

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reduce the weight of polymeric structural components and implementing FDM technology to print those optimized parts using composite filament as feedstock material[8]. Many

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researchers studied the effect of FDM process parameters like build orientation[9], raster angle[10], printing temperature[11], infill density, and deposition velocity on tensile characteristics of printed parts using PLA and ABS as feedstock material [12] [13]. Specifically, Hongbin et al.[14] observed that layer thickness played a predominant role in deciding the tensile strength of part as compared with other factors like infill density and deposition velocity. J.M. Chacón et al.[15] found out the up-right orientation had less tensile and bending strength as compared with on-edge and flat orientation. In addition to that, it was found that ductility of part decreases as layer thickness and feed-rate increases.

Various investigators studied the constitutive modelling[16][17], and inelasticity behaviour of 3D printed parts using the elasto-plastic[18] and hyperelastic-viscoplastic material model[19] with including the effect of material anisotropy, pressure sensitivity, and strain rate. Researchers also examined the yield criteria of the printed part using Hill- Tsai[23], and TsaiWu[21] failure model and the theoretical models were adequately validated with experimental data[20] [22]. The CLT model was used to predict tensile and bending stiffness of different laminate configurations printed using FDM technology and the results showed a good agreement with the test results[24][25]. Rodriguez and Thomas proposed an analytical model based on the mean void size of mesostructure of the printed part to predict in-plane

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stiffness and same was validated against homogenization model[26]. Orthotropic properties of ABS and PLA used separately in CLT model to predict in-plane stiffness of respective

laminate models, and it was reported that 4.7% to 6.6% variation is coming in between model output and experimental result[27].

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Introduction of new 3D printing techniques like multi-material stereolithography process and Multi-technology hybrid stereolithography process opened a new dimension in multi-material

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printing segment[28][29]. It is now easy to combine different materials for tailoring the Poisson ratio from positive to a negative value with the help of multi-material printing[30].

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Rupinder et al. [31]investigated various tensile characteristics of multi-material printed structure using the FDM process. Investigators reported that the design and manufacturing freedom of multi-material 3D printing process helped them in the making of functionally

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graded material[32][33] [34], low-cost multifunctional bio-prostheses[35], and soft robotic parts[36]. Among them, Sachin et al.[35] highlighted the use of PLA and conductive PLA in the printing of multifunctional prosthetic finger, where the PLA resist the external load and

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conductive PLA act as a capacitive sensor for touch screen application. Anthony R Demario[36] in his thesis demonstrated the use of conductive PLA in the making of the

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flexible joint in the legs of a miniature robot. The conductive PLA acted as a fulcrum when it was excited by the external voltage source due to its low glass transition temperature. Similarly, Mohamed Al-Rubaiai et al.[37] demonstrated the use of conductive PLA to prepare a soft actuator, where its flexibility was control by the variable stiffness mechanism. Conductive nature of the material helped to propagate thermal activation through joule heating in the actuator. This mechanism supported the actuator to tune its stiffness in the range of 1GPa at 25o C to 13.6 MPa at 80o C according to demand for holding and releasing the object. Rajendra et al.[38] explained the use of PLA in the fabrication of medical

implants, tissue engineering, orthopedic devices and its different applications in clinical usage. The striking characteristic features of PLA material like biodegradability, biocompatibility, non-toxicity, and eco-friendly made it viable for many engineering applications[39][40].

The reported literature discloses that many investigations have been done in the past to print multi-material part using different AM process and its applications to technological usage. But minimal works have been done regarding analytical modelling of tensile stiffness of multi-material 3D printed part manufactured by the FDM process and its validation. As many

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applications are focused on making the functional part using PLA and PLA conductive material, so there is a likelihood to take the advantages of both materials in a common

structure, which can meet both mechanical and functional requirements. In this paper, thrust

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is given to the following research goals :

Study the consonance of CLT in PLA/PLA CB bi-material laminate for the evaluation

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of in-plane stiffness and to validate same with experimental data. Study the average tensile properties of 3D printed specimens and laminates by

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eliminating the wall line bead or raster in printed structure. Investigate the molecular degradation of functional groups of feedstock material during the printing process by using the FTIR study. Study the influence of raster orientation on tensile properties of printed laminate parts

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and compare the average tensile properties of mono-material and bi-material 3D 

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printed laminate parts.

Investigate the fracture surfaces of bi-material laminates using scanning electron

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micrographs.

2. Analytical modelling of 3D printed laminate part using CLT In this investigation, the laminate part fabricated by the FDM process is considered as stacking of orthotropic laminas, as shown in (Fig. 1a). Where the X and Y-axis denote the orthotropic loading axis. The axis ‘1’ represents the longitudinal axis or raster axis, which indirectly describes filament extrusion direction and axis ‘2’ denotes transverse direction. The raster orientation with respect to the X-axis is indicated by angle ′𝜃′.

The relation between stress(𝜎) and strain(𝜖) for linearly orthotropic material is given by 𝑄11 𝜎11 𝑄21 𝜎22 𝜎33 𝑄31 𝜏12 = 0 𝜏13 0 {𝜏23 } [ 0

𝑄12 𝑄22 𝑄32 0 0 0

𝑄13 𝑄23 𝑄33 0 0 0

0 0 0 𝑄44 0 0

0 0 0 0 𝑄55 0

𝜖11 0 𝜖 0 22 𝜖33 0 𝜖12 0 𝜖13 0 𝑄66 ] {𝜖23 }

(1)

As in the case of CLT, in-plane orthotropic properties required to carry out the calculation of laminate mechanics, the above constitutive model (equation-1) modified to plane stress state (𝜎33 = 0, 𝜏13 = 0 &𝜏23 = 0). So the relationship between stress and strain reduced as 𝑄12 𝑄22 0

𝜖1 0 0 ] { 𝜖2 } 𝑄33 𝛾12

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𝜎1 𝑄11 { 𝜎2 } = [𝑄12 𝜏12 0

(2)

or

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{𝜎}1,2 = [𝑄]{𝜖}1,2

(3)

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In the above-said relationship between stress(𝜎) and strain(𝜖) , the [𝑄]matrix is known as reduced stiffness matrix and [𝑄] = 𝑓(𝐸1 , 𝐸2 , 𝐺12 & 𝜗12 ). Where 𝐸1 , 𝐸2 , 𝐺12 & 𝜗12 represents

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longitudinal Young's modulus along direction 1, transverse Young's modulus along direction 2, shear modulus and Poisson ratio in-plane orthotropic properties of lamina respectively as

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shown in (Fig. 1b).

The individual element in the[Q] matrix is given as follows: 𝐸

𝜗 𝐸1

𝑄11 = 1−𝜗 1 𝜗 ,𝑄12 = 𝑄21 = 1−𝜗21

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12 21

12 𝜗21

𝐸

𝜗

,𝑄22 = 1−𝜗 2 𝜗 ,𝑄33 = 𝐺12 & 𝐸12 = 12 21

1

𝜗21 𝐸2

(4)

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Stresses in orthotropic loading axis X and Y given by the relation ̃]{𝜎}1,2 {𝜎}𝑋,𝑌 = [T

(5)

̃] is known as the transformation matrix. [T or 𝜎𝑋 𝑐𝑜𝑠 2 𝜃 { 𝜎𝑌 } = [ 𝑠𝑖𝑛2 𝜃 𝜏𝑋𝑌 𝑠𝑖𝑛𝜃𝑐𝑜𝑠𝜃

𝑠𝑖𝑛2 𝜃 𝑐𝑜𝑠 2 𝜃 −𝑠𝑖𝑛𝜃𝑐𝑜𝑠𝜃

𝜎1 −𝑠𝑖𝑛(2𝜃) 𝜎 𝑠𝑖𝑛(2𝜃) ] { 2 } 𝑐𝑜𝑠 2 𝜃 − 𝑠𝑖𝑛2 𝜃 𝜏12

(6)

For a lamina that occupies the kth position in the laminate, the relationship between stress and strain given by {𝜎}𝑘 = [𝑄̅ ]𝑘 {𝜖}𝑘

(7)

or ̅ 11 𝜎𝑥 𝑘 Q ̅ 21 { 𝜎𝑦 } = [Q 𝜏𝑥𝑦 ̅ 31 Q

̅ 12 Q ̅ 22 Q ̅ 32 Q

̅ 13 𝑘 𝜖𝑥 𝑘 Q ̅ 23 ] { 𝜖𝑥 } Q 𝛾𝑥𝑦 ̅ 33 Q

(8)

Where {𝜎}𝑘 = Stress in the kth lamina

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[𝑄̅ ]𝑘 = Transformed reduced stiffness matrix for the kth lamina Moreover, for the whole laminate 𝑛

𝑛

∑{𝜎} = ∑[𝑄̅ ]𝑘 {𝜖}𝑘 ; n indicates no. of lamina in laminate 𝑘

𝑘=1

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𝑘=1

(9)

The individual coefficients in the transformed reduced stiffness matrix are follows (10)

̅ 12 = Q ̅ 21 = (Q11 + Q22 − 4Q33 )cos2 θsin2 θ + Q12 (cos 4 θ + sin4 θ) Q

(11)

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̅ 11 = Q11 cos 4 θ + Q22 sin4 θ +2(Q11 + Q33 )cos 2 θsin2 θ Q

(12)

̅ 23 = Q ̅ 32 = (Q11 − Q12 − 2Q33 )cosθsin3 θ − (Q22 − Q12 − 2Q33 )cos 3 θsinθ Q

(13)

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̅ 13 = Q ̅ 31 = (Q11 − Q12 − 2Q33 )cos3 θ sin θ − (Q22 − Q12 − 2Q33 )cosθsin3 θ Q

̅ 33 = (Q11 − Q12 − 2Q12 − 2Q33 )cos2 θsin2 θ + Q33 (cos4 θ + sin4 θ) Q

(14)

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The resultant force and moment acting on the 3D printed laminate calculated by integrating the stress function in each layer of laminate, as shown in (Fig. 2) through the thickness ′𝑡 ′ is

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given as

t

⁄2 zk n Nx σx σx k [ Ny ] = ∫ [ σy ] dz = ∑ ∫ [ σy ] dz Nxy −t⁄ τxy k=1 zk−1 τxy

(15)

2

t

⁄2 zk n Mx σx σx k [ My ] = ∫ [ σy ] z dz = ∑ ∫ [ σy ] z dz Mxy −t⁄ τxy k=1 zk−1 τxy 2

(16)

The relation between applied resultant force N and moment M and the mid-plane strain (𝜖 0 ) and curvature (𝑘 0 ) given by the following single equation as N A B ϵ0 { }=[ ]{ } M B D k0

(17)

or A13 A23 A33 B13 B23 B33

B11 B21 B31 D11 D21 D31

B12 B22 B32 D12 D22 D32

ϵ0x B13 ϵ0y B23 0 B33 γxy D13 k 0x D23 k 0y D33 ] 0 {k xy }

(18)

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A12 A22 A32 B12 B22 B32

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Nx A11 Ny A21 Nxy A = 31 Mx B11 My B21 [ B31 {Mxy }

Where n

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̅ 𝑖𝑗 k (zk − zk−1 ) Aij (the extensional stiffness matrix) = ∑ Q

(19)

k=1

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1 2 ̅ 𝑖𝑗 k (zk2 − zk−1 Bij (bending − extension stiffness matrix) = ∑ Q ) 2

(20)

k=1

n

Dij (bending stiffness matrix) =

1 3 ̅ 𝑖𝑗 k (zk3 − zk−1 ∑Q ) 3

(21)

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k=1

Using the stiffness coefficients of extensional stiffness matrix (𝐴𝑖𝑗 ) the effective in-plane stiffness (𝐸𝑒𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒 ) of laminate part can be evaluated as

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(22)

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E𝑒𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒

A11 A22 − A212 = A22

3. Experimental procedure 3.1 Equipment & Materials In this work, the Ultimaker-3 extended 3D printer was used, which mainly consists of a build plate, dual extrusion head, and X-Y-Z control mechanism. The printer can print of maximum build volume 215 x 215 x 300 mm3, printing layer resolution up to 20 µm and extruder temperature ranges from 180o C to 280o C. PLA and PLA CB filament having 2.85 mm diameter was being used for the fabrication of individual tensile, shear specimens and

laminates. The detail picture of the feedstock filaments and 3D printer shown in (Fig. 1c & 1d).

3.2 Fabrication of tensile and shear specimens The primary input parameters to CLT theory are the magnitude of orthotropic properties of the individual lamina(𝐸1 , 𝐸2 , 𝐺12 & 𝜗12). Thus to investigate the individual in-plane orthotropic properties of PLA and PLA CB, these materials were separately fed to the printer with the appropriate printing parameters as shown in Table-1. The tensile specimens were printed according to ASTM-638 type-IV standard for the measurement of longitudinal Young's modulus(E1) and transverse Young's modulus(E2 ) and Poisson’s ratio(𝜗12 ).

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Similarly, to measure the shear modulus( 𝐺12 ) specimens were printed according to ASTM D3518-94 standard. In the slicing software CURA, while designing the specimen, wall line bead or raster is appearing around the periphery of the model, as shown in (Fig. 1e). The presence of the wall line bead in the model structure is going to influence the tensile

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properties of the model. Therefore to know the effect of raster orientation on tensile

properties, it was removed from the structure of the model. The detail of printing specimens

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and the geometrical dimension of models shown in (Fig. 3a, b, c, d, e & f).

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3.3 Fabrication of individual and composite laminates

The mono-material PLA and PLA CB filament were loaded in the 3D printer at extruder-1 and extruder-2. Then individual mono-material laminates of different raster designs were

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printed using the corresponding extruder using the printing process parameter shown in Table-1. Similarly, here also the wall line thickness value made to zero to avoid the load sharing problem of wall line with infill line. As in the present investigation, the bi-material

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tensile stiffness is going to be investigated. Therefore, it is necessary to describe the procedures to design the bi-material laminate structure in slicing software. According to the

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ASTM 3039-95A standard, the dimension of laminate is 90mm x 25mm x 3.04mm, and the laminate consists of eight (8 no.s) of the lamina. Using the solid modelling software ‘ANSYS Space Claim’ first, the individual lamina model of dimension 90mm x 25mm x 0.38mm were built. Then the corresponding STL file opened in slicing software CURA and alternatively PLA and PLA CB material was assigned by selecting extruder-1 and extruder-2. After that, the individual models merged to a single model using ‘merge option’ in CURA slicing software as shown in (Fig. 4). The printing process parameters for bi-material laminate is given in Table-1. The thermal compatibility between PLA and PLA CB material

is confirmed from differential scanning calorimetry (DSC) plot, as shown in (Fig. 5). The plot is reflecting the closeness of glass transition temperature (Tg) and melting temperature (Tm) for PLA and PLA CB material, which makes them suitable for bi-material printing. The details of materials used in laminate printing and lamina/layer orientations presented in Table-2.

4. Results & Discussion 4.1 In-plane orthotropic properties of PLA and PLA CB specimen The longitudinal Young's modulus (𝐸1 ) and the transverse Young's modulus (𝐸2 ) is measured

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by performing a tensile test on 0o degree specimen and 90o raster angle specimen with a crosshead speed of 5 mm/min in UTM. The average shear modulus (𝐺12 ) of PLA and PLA CB found to be 800 MPa and 650 MPa respectively by performing the tensile test on the

shear specimen with a crosshead speed of 2 mm/min. The Poisson ratio (𝜗12 ) measured from strain gauge outputs, which were mounted in the longitudinal and transverse direction of

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ASTM D-638 standard of PLA and PLA CB sample. The corresponding value for Poisson

ratio found to be 0.3 and 0.32 for PLA and PLA CB material. The PLA 0o specimen is having

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a combination of both ductile and brittle mode of failure. The fracture area displays abrupt changes in surface area, which contains opened-up crazes and elongated beads, as shown in

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(Fig. 6a). On the other hand, the 90o specimen experienced the pure brittle mode of fracture as the failure area was flat in shape, as shown in (Fig. 6b). The details of average tensile

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properties of PLA and PLA CB presented in Table-3. By comparing the results shown in Table-3 following points can be made such as the PLA 0o specimen is 15.63% less stiff, 17.02% less strength and mainly 71.43% less ductile as

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compared with PLA feedstock filament. Similarly, PLA 90o samples is having 44.45% less strength and 85.72% less ductile as compared with parent homogeneous PLA feedstock

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filament. A similar trend also experienced in PLA CB specimens along with the average tensile properties reduced sharply. The tensile stiffness of PLA CB 0o specimen reduced by 9.69% followed by PLA CB 90o of 29.59% as compared to PLA CB feedstock filament stiffness.The strength of PLA CB 0o specimen reduced by 27.48%, ductility by 75% as compared with PLA CB feedstock filament tensile properties. Similarly, PLA CB 90o specimen showed 48.84% less strength and 85% less ductile as compare with parent PLA CB material. The tensile stiffness value for PLA CB feedstock filament reduced by 19.35%,

strength by 19.15% and breaking strain by 14.29% concerning PLA feedstock filament tensile properties. This investigation also reflects raster angle has a significant influence on the average tensile properties of the samples. The details of stress and strain behaviour for PlA and PLA CB filament materials and tensile specimens presented in (Fig. 7a & 7b). 4.2 FTIR study on feedstock filament materials and 3D printed Samples Fourier-transform infrared spectroscopy (FTIR) study is a non-destructive testing technique used to identify functional groups in the polymer, to study process-induced molecular degradation and chemical changes in microstructure. FTIR study also indirectly links microscopic examination with mechanical properties of filament materials and their 3D

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printed parts. In this investigation, the FTIR study carried out on filament materials and 3D printed samples to visualise the behaviour of different functional groups and measure their peak transmittance magnitude. To do this, filament materials and printed samples undergo FTIR testing using Thermo Scientific Nicolet iS5 spectroscope fitted with iD5 attenuated

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total reflection (ATR) detector, equipped with diamond internal reflection element. FTIR

spectra, in transmittance mode, were detected using a scanning resolution 2 cm-1 and 32 scans

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for each sample in the range of 4000-400 cm-1.

The FTIR study indicates there is less absorption of radiation energy in the functional group

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of the 3D printed sample, as shown in (Fig. 8a & 8b). The absorption peak reduction ratio for 3D printed samples and filament feedstock materials given in Table-4, which showed nearly 1% less absorption in 3D printed molecular structure. This reduction probably leads to

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polymer chain scission and crosslinking, which eventually leads to inconsistency in the microstructure. This complex phenomenon, coupled with microvoid presence in mesostructure, reduced the intra and interlayer strength in PLA 3D printed specimens, as

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shown in Table-3.

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4.3 Experimental Campaigning on laminates The models were tested in UTM machine with a crosshead speed of 2 mm/min for the measurement of Young's modulus, UTS and breaking strain. The details of average tensile properties of all models shown in Table-5. The laminate models [08]T, [(0/90)4]T& [(±45)4]T are designated as A1, A2 and A3, respectively.

4.3.1 Average tensile properties of A1, A2 and A3 model Comparisons among different model were investigated as follows. First, we compared theoretical estimation of in-plane stiffness of A1, A2 & A3 model by classical laminate theory (CLT) with experimental results. Next, we compared UTS (𝜎𝑢 ) of A1, A2 &A3 model among themselves. Finally, the breaking strain (𝜖𝑢 ) was compared among the configuration of A1, A2 & A3. 4.3.2 Comparative analysis between CLT and experimental results To know the validity of the CLT model for in-plane stiffness prediction of the 3D printed part, the following comparisons are made with different raster configuration of 3D printed

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laminate. 4.3.2.1 Laminate with 0o raster orientation

The PLA 0o specimen is having 9.1% mean variation in tensile stiffness measurement as

compared with the theoretical result by CLT. Similarly, for PLA CB 0o mean variation rose to

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11.84% and mean deviation for PLA/PLA CB composite leads to highest (14. 88%). The reason behind the increase in mean error value indicates the presence of material

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inhomogeneity and inconsistency in the microstructure of PLA by the introduction of carbon black to its phase.

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4.3.2.2 Laminate with 0o/90o raster orientation

The 0o/90o specimen of pure PLA showed 11.4 % mean variation in tensile stiffness

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measurement concerning result projected by CLT. At the same time, the mean deviation for PLA CB and PLA/PLA CB composite estimated to be 6.54% and 6.28%. This data reflects both raster orientation at different layer and the presence of carbon black mutually affect the

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tensile stiffness of the laminate.

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4.3.2.3 Laminate with 45o/-45o raster orientation This set of laminate showed minimum mean variation in PLA and PLA CB individual model and maximum mean variation in the composite model as compared with A1, A2 model. The mean variations are 0.94%, 0.3% and 19.75 % for PLA, PLA CB and PLA/PLA CB composite respectively. In this model, the composite specimen type presents the lowest tensile stiffness value as compare with PLA and PLA CB specimen individually. The reason for this cause and the excess mean variation of composite laminate (19.75%) is due to improper adhesion between PLA and PLA CB material, which fundamentally down rate the

assumptions of the classical laminate theory. This observation indicates theoretical modelling to in-plane stiffness using CLT highly depend upon raster angle, and nature bonding between 3D printed individual lamina. The detail comparisons for theoretical prediction by CLT and experimental result for all sample of A1, A2 & A3 model and error plot shown in (Fig. 9a, b & c and Fig. 10a, b & c). The investigation reflects CLT is an appropriate model to predict in-plane stiffness of 3D printed laminate made from both mono-material and bi-material with an overall average error of 9% with experimental results. The trend in error plot shows 0o and 0o/90o is having minimal standard deviation among their respective individual repetitive models. The 45o/-45o

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laminate model reflects highest in standard deviation value for their repetitive individual specimens, as shown in (Fig. 10 c).

4.3.3 Comparison among UTS of 3D printed laminates A1, A2 & A3

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The average UTS for the A1 model is highest followed by A3 and A2 model, which is

indicating raster orientation parallel to loading direction yields maximum strength. This

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inference shows that the raster orientation of individual layer of corresponding laminate plays a dominant role in determining UTS. The average UTS of PLA/PLA CB composite laminate for all model showed an intermediate result between PLA and PLA CB model. This inference

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indicates the 3D printed laminate structure follows strength prediction by the rule of the mixture used for tensile strength prediction of fibre reinforced composite. Among all the

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model A1, A2 and A3 higher amount of standard deviation shown by A2 model followed by A1 and A3 as shown in (Fig. 11a, b & c).

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4.3.4 Comparison among the braking strain of 3D printed laminates A1, A2 & A3 The laminate model A1 and A3 showed more ductility as compared with A2 model. All the

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laminates coming under the A2 model showed an average breaking strain of 1.4%, which indirectly hint this model will not be helpful for high toughness applications. The reason behind this phenomenon is the presence of 90o raster in the laminate, which is having less breaking strain for both PLA and PLA CB as described in stress-strain behaviour model (Fig. 7a & 7b). A brittle mode of failure found on all specimens of the A2 model. The pure PLA has maximum breaking strain in all the model followed by PLA/PLA CB composite and PLA CB specimen. The PLA 45o/- 45o showed highest (4.89%) breaking strain among all

individual models of A1, A2 and A3 model. The details of the error plot for breaking strain for all the models shown in (Fig. 12a, b & c).

4.4 Comparison among tensile properties of bi-materials of different raster configuration The tensile properties like elastic modulus, UTS and breaking strain of 3D printed bi-material laminates showed a greater dependence with the raster orientation in the laminate as projected in (Fig. 13a, b & c). The elastic modulus of [(0/90)4]T model reported 28.44% higher than [(±45)4]T model followed by model [08]T of 12.12% and the model elastic

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modulus magnitude enhanced at the cost of its ductility. This inference implies that the model will offer higher resistance to static load and best suit to low-strain rate applications. Among all the bi-material model, the [08]T model displayed maximum tensile strength followed by [(±45)4]T and [(0/90)4]T model. The reason behind this inference is the proper diffusion

bonding between beads of the layer of printed laminate at 0o raster orientation, which allowed

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induced stress to distribute uniformly among the beads of the laminate. The [(±45)4]T model produced 218.3% higher breaking strain than [(0/90)4]T model followed by [08]T model of

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9.7% and this property of [(±45)4]T model makes it suitable for high-strain rate applications.

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5. Fractography analysis of fracture surfaces of bi-material laminates The study of fractography analysis plays a vital role in disclosing various failure modes of fracture surfaces of specimens under different loading conditions and gives more insightful

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information for failure analysis for researchers. The fracture surfaces of 3D printed pure ABS and ABS composites specimens under tensile load were studied using SEM, and the fractography images revealed the changes in failure modes due to the presence of

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additives[41]. Similarly, here the fracture surfaces of 3D printed bi-material laminates were analysed along its fracture cross-section, and electron micrographs of failure surfaces of all

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three laminate configurations ( [08]T, [(0/90)4]T& [(±45)4]T ) showed different failure behaviours as shown in (Fig. 14a, b & c). In the [08]T laminate model PLA constituent demonstrated the presence of many opened-up crazes, quasi-cleavage facets, micro river lines, which implies both brittle and ductile mode of failures in PLAconstituent. But in the same model, thePLA CB constituent failed purely in brittle mode, which confirmed by the presence of multiple craters (Fig. 14a) in the micrographs. The presence of multiple craters in PLA CB phase arose due to the presence of carbon black in the PLA phase, which acts as a stress concentrator and eventually reduced the ductility. The carbon black in the PLA phase

blocked the prolongation of microfractures produced during plastic deformation of the models and therefore, obstruct the deformation propagation in PLA CB constituent. The [(0/90)4]T laminate model showed pure brittle fracture (Fig. 14b) as both PLA and PLA CB constituent displayed flat surface. Moreover, the PLA constituent in the model demonstrated smooth cleavage, and PLA CB constituent showed flat craters along with micro porosities at the fracture surfaces. The same model displayed the highest tensile stiffness (Fig. 13a) among all the bi-material laminate models at the cost of ductility. In the [(±45)4]T laminate model, the PLA constituent showed the number of micro dimples and curved cleavages (Fig. 14c), which eventually increased the breaking strain (Fig. 13c) of the model. On the other hand, the

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PLA CB constituent displayed multiple craters and microvoids at the failure surfaces.

6. Conclusion

In this paper, in-plane orthotropic properties(𝐸1 , 𝐸2 , 𝐺12 & 𝜗12 ) of 3D printed PLA and PLA CB specimens were calculated and used for primary input data to the CLT model. All the

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specimens and laminates were printed by removing the wall line thickness. This mechanism of wall line removal eliminated its load-bearing effect on properties of a 3D printed structure.

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Therefore, it pushed the pre-set orientated roads of a 3D printed structure solely to bear the load. This modification in design process brought robustness in 3D printed material testing

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procedures for the FDM process in a structural application. The methods for printing bimaterial demonstrated by using advanced options of slicer software CURA which will be stepping stone for new investigation in multilateral printing through the FDM process. Use of

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CLT to predict the in-plane stiffness for both mono-material and bi-material 3D printed laminate structure showed excellent validation with the experimental result except a small deviation for PLA CB mono-material structure. So this confirms the use of CLT as an

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analytical tool can be suggested to predict the in-plane stiffness of the 3D printed bi-material laminate too.

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The raster/layer orientations of the laminates demonstrated greater importance in measuring average tensile properties of laminates. Among all the laminate model ([08]T, [(0/90)4]T& [(±45)4]T ), the [08]T model exhibited better tensile properties (mean in-plane stiffness of 1807.64 MPa, mean UTS of 32.65 MPa and mean breaking strain of 4.05% ) can be considered to be a good elastic structure for tensile load-bearing applications. The PLA [(±45)4]T laminate model showed a greater amount of toughness, which can be considered as good design for high strain applications. The bi-material laminate with raster configuration [(0/90)4]T produced the highest tensile stiffness among bi-material laminate models. At the

other hand, the same [(0/90)4]T configuration showed minimum UTS (19.94 MPa) and breaking strain (1.42%) among all the bi-material models. The [(±45)4]T bi-material laminate model performed better in terms of breaking strain as compare with other models. Hence, these findings confirmed raster orientation and material nature plays a dominant role in predicting average tensile properties of the 3D printed laminate part. FTIR investigation confirmed the molecular degradation of the functional groups present in 3D printed samples by comparing the energy absorption level band with its feedstock filament material. This molecular degradation, coupled with the presence of the microvoids in mesostructure of the part caused the reduction in the mechanical properties of 3D printed

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parts. The fractography analysis on fracture surfaces of bi-material parts was investigated to understand the mode of failures and its impact on mechanical properties. It was revealed that the PLA constituent in the [08]T and [(±45)4]T bi-material model showed both modes of

failure (brittle and ductile). Whereas, the PLA CB constituent displayed a brittle mode of

fracture in all model due to the presence of the carbon black in the PLA phase. Among all the

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bi-material models, the [(±45)4]T model demonstrated several opened-up crazes and micro dimples, which eventually failed with tear fracture. These findings indicate that the

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designers/researchers need to be very careful while choosing the raster angle configuration and feedstock materials for the designing of functional polymer composite laminate using the

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FDM process.

7. Future scope

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The researchers can attempt to print the part with more numbers of materials and design the functional part with the flexibility of the FDM process. More detail experimental campaigning can be done by varying other process parameters of the FDM like layer height,

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raster angle, nozzle temperature, nozzle flow rate, etc. For better accuracy, an analytical model can be proposed to predict tensile properties of the FDM part using advanced

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composite laminate mechanics and thermal diffusion theory of polymer. Acknowledgements We are thankful to the Department of Metallurgical and Materials Engineering, Energy and Environment and Chemistry of National Institute of Technology, Trichy for extending their help in terms of testing specimens and material characterisations.

References [1]

ASTM INTERNATIONAL, ASTM F2792-12a, Rapid Manuf. Assoc. (2013) 1–3. doi:10.1520/F2792-12A.2.

[2]

S. Singh, S. Ramakrishna, R. Singh, Material issues in additive manufacturing: A review, J. Manuf. Process. 25 (2017) 185–200. doi:10.1016/j.jmapro.2016.11.006.

[3]

X. Yan, P. Gu, A review of rapid prototyping technologies and systems, CAD Comput. Aided Des. 28 (1996) 307–318. doi:10.1016/0010-4485(95)00035-6.

[4]

B. Stephens, P. Azimi, Z. El Orch, T. Ramos, Ultrafine particle emissions from

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desktop 3D printers, Atmos. Environ. 79 (2013) 334–339. doi:10.1016/j.atmosenv.2013.06.050. [5]

A. Safari, Processing of advanced electroceramic components by fused deposition

[6]

-p

technique, Ferroelectrics. 263 (2001) 45–54. doi:10.1080/00150190108225177.

S. Peters, M.O. Us, J.E. Polus, Honeycomb Cores for Aerospace Applications, 2004.

re

https://patentimages.storage.googleapis.com/3e/3e/19/f5468b0ffa5cd5/US2004004802 7A1.pdf.

Stratasys, 3D Printing a Space Vehicle, Strat. News. (2013).

lP

[7]

https://www.stratasys.com/-/media/files/casestudies/aerospace/cs_fdm_ae_nasa.pdf%0A. M.M. Mark Cotteleer, Jonathan Holdowsky, The 3D opportunity primer, March 06.

na

[8]

(2014) 20. https://www2.deloitte.com/insights/us/en/focus/3d-opportunity/the-3d-

[9]

ur

opportunity-primer-the-basics-of-additive-manufacturing.html. R.J. Zaldivar, D.B. Witkin, T. McLouth, D.N. Patel, K. Schmitt, J.P. Nokes, Influence

Jo

of processing and orientation print effects on the mechanical and thermal behavior of 3D-Printed ULTEM ® 9085 Material, Addit. Manuf. 13 (2017) 71–80. doi:10.1016/j.addma.2016.11.007.

[10] S.R. Rajpurohit, H.K. Dave, Effect of process parameters on tensile strength of FDM printed PLA part, Rapid Prototyp. J. 24 (2018) 1317–1324. doi:10.1108/RPJ-06-20170134. [11] B. Wittbrodt, J.M. Pearce, The effects of PLA color on material properties of 3-D

printed components, Addit. Manuf. 8 (2015) 110–116. doi:10.1016/j.addma.2015.09.006. [12] G.A. Ferraro, A. Corcione, G. Nicoletti, F. Rossano, A. Perrotta, F. D’Andrea, Blepharoplasty and otoplasty: Comparative sedation with remifentanil, propofol, and midazolam, Aesthetic Plast. Surg. 29 (2005) 181–183. doi:10.1007/s00266-004-00282. [13] Y. Song, Y. Li, W. Song, K. Yee, K.Y. Lee, V.L. Tagarielli, Measurements of the mechanical response of unidirectional 3D-printed PLA, in: Mater. Des., 2017: pp.

ro of

154–164. doi:10.1016/j.matdes.2017.03.051. [14] H. Li, T. Wang, J. Sun, Z. Yu, The effect of process parameters in fused deposition

modelling on bonding degree and mechanical properties, Rapid Prototyp. J. 24 (2016) 80–92.

-p

[15] J.M. Chacón, M.A. Caminero, E. García-Plaza, P.J. Núñez, Additive manufacturing of PLA structures using fused deposition modelling: Effect of process parameters on

doi:10.1016/j.matdes.2017.03.065.

re

mechanical properties and their optimal selection, Mater. Des. 124 (2017) 143–157.

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[16] M. Somireddy, A. Czekanski, C.V. Singh, Development of constitutive material model of 3D printed structure via FDM, Mater. Today Commun. 15 (2018) 143–152.

na

doi:10.1016/j.mtcomm.2018.03.004.

[17] M. Domingo-Espin, J.M. Puigoriol-Forcada, A.A. Garcia-Granada, J. Llumà, S. Borros, G. Reyes, Mechanical property characterization and simulation of fused

ur

deposition modeling Polycarbonate parts, Mater. Des. 83 (2015) 670–677.

Jo

doi:10.1016/j.matdes.2015.06.074. [18] Y. Xia, K. Xu, G. Zheng, R. Zou, B. Li, P. Hu, Investigation on the elasto-plastic constitutive equation of parts fabricated by fused deposition modeling, Rapid Prototyp. J. 25 (2019) 592–601. doi:10.1108/RPJ-06-2018-0147.

[19] P. Zhang, A.C. To, Transversely isotropic hyperelastic-viscoplastic model for glassy polymers with application to additive manufactured photopolymers, Int. J. Plast. 80 (2016) 56–74. doi:10.1016/j.ijplas.2015.12.012.

[20] M. Somireddy, A. Czekanski, Characterization of Material Behavior of the Fused Deposition Modeling Processed Parts, in: Proc. ASME 2017 12th Int. Manuf. Sci. Eng. Conf. MSEC2017 June 4-8, 2017. doi:10.1115/msec2017-2949. [21] S.H. Ahn, C. Baek, S. Lee, I.S. Ahn, Anisotropic Tensile Failure Model of Rapid Prototyping Parts - Fused Deposition Modeling (FDM), Int. J. Mod. Phys. B. 17 (2003) 1510–1516. doi:10.1142/s0217979203019241. [22] G. Alaimo, S. Marconi, L. Costato, F. Auricchio, Influence of meso-structure and chemical composition on FDM 3D-printed parts, Compos. Part B Eng. 113 (2017)

ro of

371–380. doi:10.1016/j.compositesb.2017.01.019. [23] T. Yao, Z. Deng, K. Zhang, S. Li, A method to predict the ultimate tensile strength of 3D printing polylactic acid (PLA) materials with different printing orientations,

Compos. Part B Eng. 163 (2019) 393–402. doi:10.1016/j.compositesb.2019.01.025.

-p

[24] L.C. Magalhães, N. Volpato, M.A. Luersen, Evaluation of stiffness and strength in fused deposition sandwich specimens, J. Brazilian Soc. Mech. Sci. Eng. 36 (2014)

re

449–459. doi:10.1007/s40430-013-0111-1.

[25] M. Somireddy, D.A. De Moraes, A. Czekanski, Flexural Behavior of FDM Parts:

lP

Experimental, Analytical and Numerical Study, in: Solid Free. Fabr. Symp., 2017: pp. 992–1004.

na

http://sffsymposium.engr.utexas.edu/sites/default/files/2017/Manuscripts/FlexuralBeha viorofFDMPartsExperimentalAnal.pdf. [26] J.F. Rodríguez, J.P. Thomas, J.E. Renaud, Mechanical behavior of acrylonitrile

ur

butadiene styrene fused deposition materials modeling, Rapid Prototyp. J. 9 (2003)

Jo

219–230. doi:10.1108/13552540310489604. [27] C. Casavola, A. Cazzato, V. Moramarco, C. Pappalettere, Orthotropic mechanical properties of fused deposition modelling parts described by classical laminate theory, Mater. Des. 90 (2016) 453–458. doi:10.1016/j.matdes.2015.11.009.

[28] R.B. Wicker, E.W. MacDonald, Multi-material, multi-technology stereolithography: This feature article covers a decade of research into tackling one of the major challenges of the stereolithography technique, which is including multiple materials in one construct, Virtual Phys. Prototyp. 7 (2012) 181–194.

doi:10.1080/17452759.2012.721119. [29] R.R. Ma, J.T. Belter, A.M. Dollar, Hybrid Deposition Manufacturing: Design Strategies for Multi-material Mechanisms Via Three-Dimensional Printing and Material Deposition, J. Mech. Robot. 7 (2015) 021002. doi:10.1115/1.4029400. [30] D. Chen, X. Zheng, Multi-material Additive Manufacturing of Metamaterials with Giant, Tailorable Negative Poisson’s Ratios, Sci. Rep. 8 (2018) 1–8. doi:10.1038/s41598-018-26980-7. [31] R. Singh, R. Kumar, I. Farina, F. Colangelo, L. Feo, F. Fraternali, Multi-material

(Basel). 11 (2019) 1–14. doi:10.3390/polym11010062.

ro of

additive manufacturing of sustainable innovative materials and structures, Polymers

[32] Y. Yang, Y. Chen, Y. Li, Z. Wang, Y. Li, Novel Variable-Stiffness Robotic Fingers with Built-In Position Feedback, Soft Robot. 4 (2017) 338–352.

-p

doi:10.1089/soro.2016.0060.

re

[33] B. Nicholas, W., T. Michael, T., O. Johannes, T., B., W. James, C., M. Bobak, B. Katia, W. George, M., W. Robert, J., A 3D-printed, functionally graded soft robot

lP

powered by combustion, Science (80-. ). 349 (2015). doi:10.1126/science.aac5894. [34] K. Zhang, M.H. Ge, C. Zhao, Z.C. Deng, X.J. Xu, Free vibration of nonlocal Timoshenko beams made of functionally graded materials by Symplectic method,

na

Compos. Part B Eng. 156 (2019) 174–184. doi:10.1016/j.compositesb.2018.08.051. [35] S. Bijadi, E. De Bruijn, E.Y. Tempelman, J. Oberdorf, Application of multi-material

ur

3D printing for improved functionality and modularity of open source lowcost prosthetics - A case study, Front. Biomed. Devices, BIOMED - 2017 Des. Med.

Jo

Devices Conf. DMD 2017. (2017) 2017–2019. doi:10.1115/DMD2017-3540. [36] A.R. Demario, Submitted by In partial fulfillment of the requirements For the Degree of Master of Science Colorado State University Fort Collins , Colorado Summer 2018 Master ’ s Committee Advisor : Jianguo Zhao Mitchell Stansloski Anthony Maciejewski, Colorado State University, 2018. https://mountainscholar.org/bitstream/handle/10217/191249/DeMario_colostate_0053 N_14715.pdf?sequence=1.

[37] M. Al-Rubaiai, T. Pinto, C. Qian, X. Tan, Soft actuators with stiffness and shape modulation using 3D-printed conductive polylactic acid material, Soft Robot. 6 (2019) 318–332. doi:10.1089/soro.2018.0056. [38] R.P. Pawar, S.U. Tekale, S.U. Shisodia, J.T. Totre, A.J. Domb, Send Orders for Reprints to [email protected] Biomedical Applications of Poly(Lactic Acid), Rec. Pat. Regen. Med. 4 (2014) 40–51. https://www.ingentaconnect.com/contentone/ben/rpgm/2014/00000004/00000001/art0 0004?crawler=true.

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[39] V. Nagarajan, A.K. Mohanty, M. Misra, Perspective on Polylactic Acid (PLA) based Sustainable Materials for Durable Applications: Focus on Toughness and Heat Resistance, ACS Sustain. Chem. Eng. 4 (2016) 2899–2916. doi:10.1021/acssuschemeng.6b00321.

-p

[40] S. Farah, D.G. Anderson, R. Langer, Physical and mechanical properties of PLA, and their functions in widespread applications — A comprehensive review, Adv. Drug

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Deliv. Rev. 107 (2016) 367–392. doi:10.1016/j.addr.2016.06.012. [41] A.R. Torrado Perez, D.A. Roberson, R.B. Wicker, Fracture surface analysis of 3D-

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printed tensile specimens of novel ABS-based materials, J. Fail. Anal. Prev. 14 (2014)

Jo

ur

na

343–353. doi:10.1007/s11668-014-9803-9.

List of figures

(a)

Y

Filament

Z(3) Head

T(2)

L(1)

Heater Nozzle Platform

Deposit

X

(c)

(b) T(2)

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Y

Z(3)

L(1)

Cross-sectional area of bead

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Printed bead

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X

(e)

Wall line

Wall line direction

Raster direction Loading direction

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(d)

Fig. 1. (a) Process modelling of FDM technique and laminate model of FDM part showing orthotropic axis,longitudinal axis, transverse axis and raster orientation, (b) an individual layer of FDM part represents as the orthotropic lamina, (c) feedstock filament materials, (d) 3D printer and (e) printed specimen with and without wall line.

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Fig. 2. Stacking of individual printed layers and their position with respect to the mid-plane

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re

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axis.

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Fig. 3. (a) PLA & PLA CB 0o specimen, (b) PLA & PLA CB 90o specimen, (c) PLA & PLA CB 45o /-45o specimen, (d) dimension of laminate model, (e) dimension of shear specimen

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8 layers

Fig. 4. Slicing model of bi-material part and 3D printed bi-material part.

8 layers

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and (f) dimension of tensile specimen.

PLA filament

22

Melting zone

Heat flow [MW]

21.5

𝛿𝑇𝑚 ≅ 15°𝑐

𝛿𝑇𝑔 ≅ 5°𝑐

21

PLA CB filament

Glass Transition zone

20.5 20 19.5 19

Crstalization zone

18.5 0

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300

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Temperatue [oc]

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Fig. 5. Differential scanning calorimetry (DSC) plot for PLA and PLA CB filament.

Fig. 6. SEM image of the fracture surfaces of tensile specimens. (a) 0o raster angle and (b)

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90o raster angle.

(b)

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(a)

Fig. 7. Stress-strain behaviour of filament materials and tensile specimens. (a) PLA and (b)

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PLA CB.

(b)

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(a)

Fig. 8. Comparision of Fourier-transform infrared (FTIR) spectra between (a) PLA CB filament & PLA CB 3D printed Sample and (b) PLA filament & PLA 3D printed sample.

(c)

(b)

In-plane stiffness (MPa)

(a)

PLA

PLA CB

PLA / PLA CB

PLA

PLA CB

PLA / PLA CB

PLA

PLA / PLA CB

450/- 450 laminate

00/900 laminate

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00 laminate

PLA CB

Fig. 9. Comparision between CLT value and mean experimental value for different lamina orientation (a) [08]T lamina orientation, (b) [(0/90)4]T lamina orientation and (c) [(±45)4]T

(a)

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lamina orientation.

(c)

PLA

na

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re

In-plane stiffness (MPa)

(b)

PLA CB

PLA/ PLA CB

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00 laminate

PLA

PLA CB

PLA/ PLA CB

00/900 laminate

PLA

PLA CB

450/- 450 laminate

Fig. 10. Error plot for experimental stiffness value (a) [08]T lamina orientation, b) [(0/90)4]T

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lamina orientation and (c) [(±45)4]T lamina orientation.

PLA/ PLA CB

(b)

(c)

UTS (MPa)

(a)

PLA

PLA CB

PLA/ PLA CB

PLA

00 laminate

PLA CB

PLA

PLA/ PLA CB

PLA CB

PLA/ PLA CB

450/- 450 laminate

00/900 laminate

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Fig. 11. Error plot for experimental UTS value (a) [08]T lamina orientation b) [(0/90)4]T lamina orientationand (c) [(±45)4]T lamina orientation.

(c)

(b)

PLA

PLA CB

PLA/ PLA CB

na

00 laminate

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re

-p

Breaking strain (%)

(a)

PLA

PLA CB

PLA/ PLA CB

00/900 laminate

PLA

PLA CB

450/- 450 laminate

Fig. 12. Error plot for experimental braking strain value (a) [08]T lamina orientation, b)

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[(0/90)4]T laminaorientation and (c) [(±45)4]T lamina orientation.

PLA/ PLA CB

(c)

UTS (MPa)

Breaking strain (%)

(b)

In-plane stiffness (MPa)

(a)

PLA/ PLA CB 00

PLA/ PLA CB 00/900

PLA/ PLA CB 450/- 450

PLA/ PLA CB 00

PLA/ PLA CB 00/900

PLA/ PLA CB 450/- 450

PLA/ PLA CB 00

PLA/ PLA CB 00/900

Fig. 13. Overall mechanical properties of bi-material laminate models. (a) stiffness plot, b)

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UTS plot and (c) breaking strain plot.

Fig. 14. SEM images of the fractures of the 3D printed bi-material laminate models. (a) [08]T lamina orientation, b) [(0/90)4]T lamina orientation and (c) [(±45)4]T lamina orientation.

PLA/ PLA CB 450/- 450

List of tables

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Table 1. FDM process parameters for printing of specimens and laminates

Mono-material laminate

Tensile and shear specimen PLA Shear specimen

Tensile specimen

Layer thickness (mm)

0.4

0.35

0.4

Road width (mm)

0.4

0.4

Infill pattern

0.38

0.4

0.4

0.4

0.4

0.35

lP

0.4

0

0

0

0

0

100

100

100

100

100

100

Lines

Lines

Lines

Lines

Lines

Lines

Lines

200

200

210

210

200

210

210

Build plate temperature (oC)

70

70

70

70

70

70

70

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Printing temperature (oC)

100

0.38

PLA laminate

0

na

Infill density (%)

0.38

Shear specimen

re

Tensile specimen

Number of wall line 0 count

PLA CB laminate

Bimaterial laminate

PLA CB

-p

Process parameters

70

70

70

70

70

70

70

Print speed (mm/s)

Table 2. Different laminate configurations and their feedstock material Serial no.

Material used in laminate printing

Layer/Lamina orientations

1

PLA

[08]T, [(0/90)4]T& [(±45)4]T

2

PLA CB

[08]T, [(0/90)4]T& [(±45)4]T

3

PLA & PLA CB

[08]T, [(0/90)4]T& [(±45)4]T

Average tensile properties of PLA and PLA CB specimens UTS

[MPa]

[MPa]

PLA feedstock filament

2430

42.3

PLA 0o

2050

35.1

PLA 90o

1460

1770

PLA CB 90o

1380

lP

PLA CB 0o

Table 4.

[mm/mm] 0.14 0.04

23.5

0.02

34.2

0.12

24.8

0.03

17.5

0.018

re

PLA CB feedsock filament 1960

Breaking Strain

-p

Young’s modulus

Specimen type

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Table 3.

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Reduction in the intensity of the absorption band at different wavenumbers of feedstock material and 3D printed specimen

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Reduction ratio in the

intensity of the Absorption Band

Reduction

Reduction ratio in the

Reduction

ratio

intensity of the Absorption

ratio

Band 1.17

I1749 PLA 3D printed Sample I1749 PLA filament

1.018

I1179 PLA CB 3D printed Sample I1179 PLA CB filament

1.14

I1181 PLA 3D printed Sample I1181 PLA filament

1.017

I1079 PLA CB 3D printed Sample I1079 PLA CB filament

1.15

I1083 PLA 3D printed Sample I1083 PLA filament

1.012

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I1747 PLA CB 3D printed Sample I1747 PLA filament

*I1750indicates the magnitude of Transmittance (%) at 1750 cm-1 wave number in the FTIR spectrum

Table 5.

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Average tensile properties of mono and bi-material laminates at different raster angle Young’s modulus [MPa]

UTS [MPa]

Breaking Strain [%]

PLA 0o

2236.49 ± 45.09

41.47 ± 2.18

4.49 ± 0.35

PLA CB 0o

1560.42 ± 61.59

21.36 ± 1.45 35.09 ± 4.56

4.12 ± 0.10

Specimen type

PLA /PLA CB Composite 0o

-p

A1 model

3.56 ± 0.07

1959.47 ± 47.02

21.13 ± 5.28

1.49 ± 0.21

1680.19 ± 10.08

15.23 ± 0.26

1.34 ± 0.06

1823.91 ± 66.54

19.93 ± 1.79

1.41 ± 0.06

38.22 ± 1.79

4.89 ± 0.30

21.43 ± 1.74

3.69 ± 0.27

re

1625.99 ± 77.94

lP

A2 model

PLA CB 0o/90o

na

PLA 0o/90o

ur

PLA /PLA CB Composite 0o /90o

Jo

A3 model

PLA 45o/-45o

PLA CB 45o/-45o PLA /PLA CB Composite 45o /-45o

1883.60 ± 160.79 1626.99 ± 78.67 1419.40 ± 81.54

29.08 ± 0.96

4.51 ± 0.43

ro of

-p

re

lP

na

ur

Jo