printing a solid part with varying material properties; the purpose ... Ferreira, A.J.M. MATLAB Codes for Finite Element Analysis: Solids and Structures. Dordrecht: ...
Designing Material Property Distribution for 3D Printing Technology Linda Leben PI: Anthony Waas, PhD Co-PI: Royan D’Mello, PhD
Motivation
Finite Element Optimization
Accomplishments
Design with conventional, homogeneous materials is limited to finding an ideal geometry to fit a given engineering purpose. These designs are driven by geometric discontinuities such as holes, notches, etc. which cause stress concentrations that lead to failure. Reinforcing these regions often leads to increased mass.
Material: MakerJuice G+ Yellow Photoresin Young’s modulus 0.9 GPa < E < 1.5 GPa Mesh refined to capture gradients in optimized design
By optimizing Young’s modulus throughout a plate with hole to minimize strain energy gradients, compared to an equivalent homogeneous plate: • Peak stress, strain, and strain energy are reduced • Stress and strain are less localized • Stress concentration factor reduced from 3.10 to 1.89
Stress, σx (MPa)
y x
1 𝑒 𝑒 𝑒 𝑊 = 𝜎𝑖𝑗 𝜀𝑖𝑗 2 𝑒 𝐺 = max( 𝛻𝑊 ) ′ 𝑆𝑜𝑙𝑣𝑒 𝑓𝑜𝑟 𝑌𝑜𝑢𝑛𝑔 𝑠 𝑚𝑜𝑑𝑢𝑙𝑢𝑠 𝑎𝑡 𝑐𝑜𝑛𝑡𝑟𝑜𝑙 𝑝𝑜𝑖𝑛𝑡𝑠 𝑡ℎ𝑎𝑡 𝑚𝑖𝑛𝑖𝑚𝑖𝑧𝑒𝑠 𝐺, 𝑠𝑢𝑏𝑗𝑒𝑐𝑡 𝑡𝑜 𝐸𝑚𝑖𝑛 ≤ 𝐸 ≤ 𝐸𝑚𝑎𝑥
Finite Element Results
Strain Energy, W (MPa)
Optimized Young’s Modulus (MPa)
Solution independent of mesh, initial guess
However, new advancements in 3D printing allow for printing a solid part with varying material properties; the purpose of this project is to establish methods for finding an “optimal” configuration of material property distribution that minimizes high gradients.
Stress, σx (MPa) Homogeneous Plate Optimized Plate
Implication: 3D printing enables engineers to not only design for an optimal geometry, but also for optimal material property distribution. This allows for weight savings and flexibility in design.
Future Work
Vat Photopolymerization Strain, εx (MPa) Homogeneous Plate Optimized Plate
• Validate results by tensile testing homogeneous and optimized plate designs, observe changes in strain distribution with Digital Image Correlation (DIC) • Obtain tensile strength data by testing dogbone specimens printed at different light intensities
motor photoresin
• Project grayscale image onto vat of photoresin • Differences in light intensity lead to changes in crosslink density • Can achieve custom configuration of Young’s modulus and strength • Work underway to test 3D printed designs
build plate
Strain Energy, W (MPa) Homogeneous Plate Optimized Plate
• Study effect on failure modes and crack propagation • Investigate other applicable 3D printing technologies
Acknowledgments projector
Note scale difference: necessary in order to visualize changes in gradients despite dramatic reduction in peak value
We gratefully acknowledge Dr. John Feo and Dr. Andrew Lumsdaine, Pacific Northwest National Laboratory for their interest and support of this project. We also acknowledge Johanna Jesse Schwartz for her assistance in 3D printing designs and conducting experiments, and Dr. A.J. Boydston for his interest and support of this project.
References Peterson, G. I., Schwartz, J. J., Zhang, D., Weiss, B. M., Ganter, M. A., Storti, D. W., and Boydston, A. J. "Production of Materials with Spatially-Controlled Cross-Link Density via Vat Photopolymerization." ACS Applied Materials & Interfaces 8.42 (2016): 29037-43. Filisko, F., Filisko, D., Juggernauth, K. R., and Waas, A. Dispersion Method For Particles in Nanocomposites and Method of Forming Nanocomposites. Patent US 20110064940A1. 17 Mar. 2011. Ferreira, A.J.M. MATLAB Codes for Finite Element Analysis: Solids and Structures. Dordrecht: Springer Netherlands, 2009.
