Scale-dependent failure of stereolithographic polymer microtrusses in three-point bending

Microtrusses fabricated by a combination of stereolithography and nanocrystalline electrodeposition are composites at both a global architectural scale and at an individual strut scale. This fabrication route is especially attractive in producing high performance lightweight materials because the key stages of forming optimally efficient templates and depositing ultra high strength material are fully decoupled. Using novel 3-D printing techniques, this study analyzes microtrusses built bottom-up from photopolymerizable polymer where the complex structure can be constructed of unit cells a few millimeters in length. While the predicted failure mechanisms matched the experimental observations, deterministic energetic size effects were needed to account for the critical loads. For strut radii <5 × the 3-D printer layer thickness, stochastic size effects became important.