Compression behaviours of 3D-printed CF/PA metamaterials : experiment and modelling

This study characterises the compressive behaviours of 3D-printed carbon fibre (CF) reinforced polyamide (PA) composite metamaterials with negative Poisson's ratio (NPR) or enhanced effective elastic modulus (EEEM), which were designed via a multidisciplinary approach and additively manufactured with fused filament fabrication. The continuous carbon reinforced PA (CCF/PA) metamaterials are compared to those made of short carbon fibre reinforced PA (SCF/PA) when subjected to in-plane compression. A numerical model based on continuum damage mechanics is developed to describe the response and failure of the 3D-printed CCF/PA composites while another one based an elastic-plastic model is developed for the 3D-printed SCF/PA parts. For metamaterials with NPR, the stiffness, peak force, energy absorption (EA) and specific energy absorption (SEA) of CCF/PA metamaterials are respectively 152.1%, 90%, 107.6% and 86%, respectively, larger than those of SCF/PA, while the SCF/PA metamaterials can reach a greater NPR (about −0.3) than CCF/PA (−0.2 ~ −0.1). For composites with EEEM, the stiffness, peak force, EA and SEA of CCF/PA are significantly improved by 433.3%, 183.3%, 228.7% and 208.2%, respectively, in comparison to those of SCF/PA. Based on experimental observation and numerical simulation, matrix failure is found to be predominant for CCF/PA NPR and EEEM composites.