Monday  |  Executive AB  |  01:40 PM–02:00 PM

#19275, Applications of Composite Strength Theory for Predicting the Failure Strengths of 3D Printing Polymers

Because more and more 3D printing materials are being used in load-bearing structures, their mechanical properties are being extensively studied. Composite laminates and 3D printing materials both have layered structures, so their failure has some similarities. Although the Tsai–Hill composite strength criterion is useful for predicting the strengths of some 3D printing polymers made with fused filament fabrication (FFF), our new experimental and theoretical studies showed that this criterion has some limitations in predicting the strengths of other 3D printing polymers. Moreover, the Tsai–Hill criterion was derived from plasticity theory to predict the yield strength, whereas the experimental data reported in previous papers were the ultimate strengths of FFF polymers. These two strengths were close only when the plasticity was small. In this paper, a new quadratic strength criterion was employed to predict a conservative lower bound for the strengths of polymers made with FFF and selective laser sintering (SLS). Interestingly, the scope of this study unexpectedly widened from strength research to fracture mechanics research because dynamic crack branching was observed in SLS specimens under static tension—a novel phenomenon among 3D printing materials. Crack branching not only followed previous crack branching rules, such as rules on the crack speed and energy release but also presented new challenges for dynamic fracture mechanics theory.

Luoyu Xu   Ningbo University