Modelling and optimisation of TPMS-based lattices subjected to high strain-rate impact loadings

Lattices structures show promising applications in aerospace, biomedical and defence sectors, in which high energy absorption and lightweight structures are required. This work studies Triply Periodical Minimal Surfaces (TPMS) with potential for impact engineer applications, focusing on material characterisation, modelling and performance optimisation. For this purpose, stainless steel 316 L lattice samples made by additive manufacturing were tested in a wide range of strain-rates and various building directions using a universal testing machine and Split Hopkinson Pressure Bar, equipped with a Digital Image Correlation system. Then, the obtained properties were implemented in an explicit finite element model and validated against experimental results related to different TMPS topologies and impact scenarios. A theoretical model is also proposed to predict the TPMS-based lattices quasi-static and impact responses up to the densification threshold. Finally, the validated numerical models were used to predict the behaviour of several functionally graded TPMS topologies, indicating the architectures with superior impact performance. The graded topologies were then manufactured and experimentally tested. The results indicate that graded topologies exhibit up to 18% higher energy absorption when compared to their non-graded counterparts. The theoretical and numerical models developed in this paper provide an effective approach for designing and predicting high energy absorption architectures subjected to quasi-static and impact loadings.