This document is downloaded from DR‑NTU (https://dr.ntu.edu.sg)Nanyang Technological University, Singapore.

Discrete homogenization of fused deposition modeling parts using the finite element method

Ravindrababu, Suraj; Makam, Raama

2018

Ravindrababu, S., & Makam, R. (2018). Discrete homogenization of fused depositionmodeling parts using the finite element method. Proceedings of the 3rd InternationalConference on Progress in Additive Manufacturing (Pro‑AM 2018), 589‑594. doi:10.25341/D4TS39

https://hdl.handle.net/10356/88668

https://doi.org/10.25341/D4TS39

© 2018 Nanyang Technological University. Published by Nanyang Technological University, Singapore.

Downloaded on 20 Jan 2021 22:32:41 SGT

ABSTRACT: This article deals with the determination of the effective elastic properties of fused deposition modeling (FDM) parts using the finite element method. As an introduction to the process, the analysis is performed on parts which are oriented in the XY-plane and the build direction in the Z axis, referred in this article as face-up samples. In this approach, a representative volume element (RVE) is created for different raster angles of the printed part in the commercial finite element solver, Abaqus. Orthotropic constitutive model is considered, and the nine elastic constants are computed using the RVE by applying periodic boundary conditions. Finally, three-point bend test is conducted, on an FDM printed beam and the physical tests are validated with simulations using the formed orthotropic material model through simulations.

KEYWORDS: Mechanical characterization; Fused Deposition Modeling; Multiscale modeling approach; Finite Element method; Additive Manufacturing

1. INTRODUCTION: Fused Deposition Modeling (FDM) is a type of additive manufacturing process (AM) where a thermoplastic material in a semi-molten state is deposited in layers to fabricate parts modeled in a CAD environment. AM methodology, especially FDM, has gained immense interest among designers owing to their capability to realise complex designs with reduced material wastage and almost no tooling costs (Chua, Leong et al. 2003). In the AM process, the choice of material and the manufacturing process are highly coupled, and they dictate the mechanical performance of the fabricated part. Moreover, AM techniques are still not refined and some uncertainties, both aleatory and epistemic, may arise. It becomes inefficient to analyze these aberrations at the macro-level or the component level owing to their large and complex morphology. Hence, efficient methodologies have to be established for studying material behaviour and processes at micro and nano level. Also, this perspective might yield dividends in vital research areas. Some of the topics which can be explored include the influence of bead shape and size on the mechanical properties and for the identification of critical regions at the atomistic levels to provide reinforcements at the nano/micro level (use of carbon nanotubes at the micro level) which are of interest currently. Multiscale computational modeling of materials (MSM) has been adopted in the field of AM technology to simulate the manufacturing process and for the homogenization to predict effective material properties (Li, Zhou et al. 2018). However, the approach has rarely been adopted for the prediction of mechanical constants for FDM printed parts. This paper focusses on developing a

DISCRETE HOMOGENIZATION OF FUSED DEPOSITION MODELING PARTS USING THE FINITE ELEMENT METHOD

SURAJ RAVINDRABABU Singapore Centre for 3D Printing,

Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798

MAKAM RAAMA Graduate Academic Intern, School of Mechanical

and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798

RAAMA MAKAM

589

Proc. Of the 3rd Intl. Conf. on Progress in Additive Manufacturing (Pro-AM 2018) Edited by Chee Kai Chua, Wai Yee Yeong, Ming Jen Tan, Erjia Liu and Shu Beng TorCopyright © 2018 by Nanyang Technological UniversityPublished by Nanyang Technological University ISSN: 2424-8967 :: https://doi.org/10.25341/D4TS39

multiscale finite element (FE) approach using periodic boundary conditions in the commercial FE package ABAQUS 2016. The highlight of this work is that it is computationally inexpensive and does not require the use of additional software packages, such as TexGen or BSAM, to provide the necessary boundary conditions for solving such problems. The predicted properties using the method is validated by conducting physical tests on a face-up sample (sample is oriented in the XY plane on the print bed as shown in Fig. 1). The Cubicon 3DP-110F (Single) FDM printer is used with acetonitrile butadiene styrene (ABS) filament. The settings are set to the default values as suggested by the accompanied slicer when creating the STL file.

Figure 1. Face-up tensile samples at 0 and 45-degree orientation on the print bed

2. BACKGROUND Literature is abundant for the experimental determination of mechanical properties for an FDM printed part (Chin Ang, Fai Leong et al. 2006). However, the method of homogenization of FDM parts is yet to be analyzed intensely. Numerical or analytical homogenization is the process of predicting macroscopic or component level properties of materials which have periodic micro/nanostructures. Analytically, methods such as the Mori-Tanaka or Fast Fourier Transform (FFT) is used while the numerical analysis involves the use of the FE method. Such approaches are adopted to predict the linear and non-linear behavior of composite materials (Wang, Roy et al. 2017, Zhong, Suraj et al. 2017). Concerning FDM, the interest of analyzing mesostructures of an FDM printed part is still nascent but initial works can be identified at the start of the century (Rodriguez, Thomas et al. 2000). The article highlights the vital effect of mesostructure parameters such as the void density and fiber to fibre bonding. Also, it determines the optimal settings for a Stratasys 1600 machine for minimum void density and optimal fibre to fibre bonding. The effect of a change in mesostructure arrangement and chemical composition on the performance of FDM components is studied in (Alaimo, Marconi et al. 2017). Experimental analysis results in the consumption of materials which might not be cost effective when working with industrial grade printers and materials. The tensile behaviour of FDM printed parts is studied by reconstructing computational models of the ASTM D638 samples in ABAQUS. Instead of depicting the computational model as a homogeneous volume, it comprised of filaments arranged as observed in the microscopic studies. The implicit scheme is used in the analysis, and a huge disadvantage is that it requires high computational time and space (Garg and Bhattacharya 2017). The use of FE packages to perform multiscale analysis on FDM parts is demonstrated in (Sheth, Taylor et al. 2017). The article shows the use of the MSM technique to study the variation of raster angles on the mechanical performance of the part. For the construction of the mesostructure, ABAQUS was used, and concurrently, BSAM was used to solve the multiscale problem. Evidently, the proposed methodology is not computationally efficient since multiple licenses have to utilized to obtain the CAD model of the mesostructure and solve it. Similar works on the topic of multiscale simulations

Chee Kai Chua, Wai Yee Yeong, Ming Jen Tan, Erjia Liu and Shu Beng Tor (Eds.)

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(1)

The reaction forces on the constrained faces are computed and using the data, Young’s modulus, shear modulus and the Poisson’s ratio could be found out through the following Eq. 2-5.

(2)

(3)

(4)

(5)

The boundary conditions imposed on the RVE for predicting E1 values, the corresponding result which highlights the critical regions in a mesostructured is shown in Fig. 3. The obtained elastic properties are shown in Table 1.

Figure 3. RVE and critical regions for applied displacement in x-direction

Table 1. Engineering constants determined through the multiscale study for a face-up sample

oriented at 0 degrees in the print bed

Elastic Mechanical Properties determined through simulation Values Young’s Modulus in direction 1, E1 1731 MPa Young’s Modulus in direction 2, E2 1681 MPa Young’s Modulus in direction 3, E3 548 MPa

Shear Modulus (plane xy), G12 711 MPa Shear Modulus (plane yz), G23 344.41 MPa

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will be aimed at predicting the failure modes near the critical regions. Secondly, the uncertainties have to be quantified and their contribution to the mechanical performance of the FDM part will be analysed. Design of Experiments (DOE) approaches will be used initially and will be further extended to study through advanced statistical models like Kriging surrogate models or Polynomial chaos expansion (PCE). 7. REFERENCES

Alaimo, G., S. Marconi, L. Costato and F. Auricchio (2017). "Influence of meso-structure and chemical composition on FDM 3D-printed parts." Composites Part B: Engineering 113: 371-380. Chin Ang, K., K. Fai Leong, C. Kai Chua and M. Chandrasekaran (2006). "Investigation of the mechanical properties and porosity relationships in fused deposition modelling-fabricated porous structures." Rapid Prototyping Journal 12(2): 100-105. Garg, A. and A. Bhattacharya (2017). "An insight to the failure of FDM parts under tensile loading: finite element analysis and experimental study." International Journal of Mechanical Sciences 120: 225-236. Ji, X., A. M. Khatri, E. S. Chia, R. K. Cha, B. T. Yeo, S. C. Joshi and Z. Chen (2014). "Multi-scale simulation and finite-element-assisted computation of elastic properties of braided textile reinforced composites." Journal of Composite Materials 48(8): 931-949. Park, S.-i. and D. W. Rosen (2015). Quantifying mechanical property degradation of cellular material using as-fabricated voxel modeling for the material extrusion process. Annual solid freeform fabrication symposium, Austin. Rezayat, H., W. Zhou, A. Siriruk, D. Penumadu and S. Babu (2015). "Structure–mechanical property relationship in fused deposition modelling." Materials Science and Technology 31(8): 895-903. Rodriguez, J. F., J. P. Thomas and J. E. Renaud (2000). "Characterization of the mesostructure of fused-deposition acrylonitrile-butadiene-styrene materials." Rapid Prototyping Journal 6(3): 175-186. Sheth, S., R. M. Taylor and H. Adluru (2017). "Numerical Investigation of Stiffness Properties of FDM Parts as a Function of Raster Orientation." Vigliotti, A. and D. Pasini (2012). "Stiffness and strength of tridimensional periodic lattices." Computer methods in applied mechanics and engineering 229: 27-43. Wang, C., A. Roy, V. V. Silberschmidt and Z. Chen (2017). "Modelling of Damage Evolution in Braided Composites: Recent Developments." Mechanics of Advanced Materials and Modern Processes 3(1): 15. Zhong, Y., R. Suraj, C. Wang, E. S. M. Chia, S. C. Joshi and Z. Chen (2017). "Damage advancement behavior in braided composite structures for mini aerial vehicles." Mechanics of Advanced Materials and Structures: 1-12.

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