Influences of low-temperature aging on mechanical performances of bio-inspired PLA composites sandwich structures prepared via multi-material additive manufacturing

A nacre-like honeycomb/gap sandwich structure with crayfish-claw-inspired helical lamination configurations is proposed, aiming to enhance fracture resistance performances. The four-point bending test samples with this biomimetic structure are additively manufactured using high-stiffness glass fiber-reinforced polylactic acid (GF/PLA) to fill the honeycomb sections, and electrically carbon black polylactic acid (CB/PLA) to fill the gaps, employing multi-material fused filament fabrication. Additionally, a low-temperature environmental aging test is conducted to assess the bending performance of the bio-inspired samples under cold conditions. Mechanical measurements revealed that, under exposure to temperatures as low as −50°C, the bending strength of the bioinspired-structural samples initially increased 30%–70% before decreasing over approximately 2 weeks, while the mechanical stiffness remained relatively stable. By the CB/PLA material, the internal fracture of the bending samples was able to be detected by measuring the in situ resistance of the sample during the test. A difference exceeding 10 times in resistance was observed between pre-failure and post-failure samples. The results presented above imply a promising design for mechanical armors for exoskeleton or unmanned robots that serve in extreme low temperature conditions, as they exhibited enhanced fracture resistance to cold environments yet possessed self-recognition in cracks and failures.