Anthropo-fidelic behavior of elastic-plastic lattice structures. (March 2023) - Haney, Christopher W.
Abstract: Vat photopolymerization is used to construct triply periodic minimal surfaces (TPMS) to match human heel pad stiffness. Five cell types are investigated at varying relative densities modeled to fulfill the roles of the two heel pad tissue constituents: the macrochamber and microchamber. Two photosensitive polymers (elastic 50A and flexible 80A) are tested in uniaxial compression to characterize the toughness and energy absorption apropos cell geometry and approximate density of a latticed volume using a Hookean approach and beam theory. This work substantiates the suitability of latticed models to reach the stiffness of the heel pad chambers. A microchamber (E = 60- 450 kPa ) and macrochamber ( E=26- 46 kPa ) stiffness response is capable of being modeled with the use of elastic-plastic 50A ( E=26.7-526. 4 kPa ) cellular solids of varying relative density. Models like the Schwarz80A at relative density ( ρ*/ρ s ) ∼ 0.5 showed a comparable modulus of toughness (T=4. 126 MPa ) to the solid samples (T=7. 5161 MPa ) . The Gyroid lattice consistently showed the capability of matching solid sample energy absorption rates in the 50A, and to outperform the solid samples in energy absorption for the 80A material. Comparing experimental and elastic-plastic theoretical results for the plateau stress and Young's modulus highlights the current model inadequacies for additively manufactured polymers. These findings can have practical applications in other areas such as light-weighting, structural design, ballistics, and soft robotics. Highlights: Vat photopolymerization is used to construct triply periodic minimal surfaces (TPMS) to match human heel pad stiffness. Five cell types are investigated at varying relative densities modeled to fulfill the roles heel pad tissue constituents. Lattices modulus of toughness and energy absorption capabilities were also evaluated. Findings suggest an effective path to creating polymer structures with anthrop-fidelic mechanical properties.