Biomimetic additive manufactured polymer composites for improved impact resistance

Biological composites, like nacre and bone, have captured the interest of the scientific community for their outstanding ability to amalgamate a host of properties such as stiffness, strength, toughness, and impact resistance. Nacre, which is composed of 95 wt.% mineral content and 5 wt.% soft biopolymeric matrix, has a toughness orders of magnitude greater than its mineral phase while having to sacrifice very little in stiffness. Consequently, researchers are aiming to mimic the structure of nacre to design tough and strong composite materials with superior properties. However, most of the experiments and simulations of nacre-like composites are confined to simple tension or compression loadings. We hypothesize that nacre-like composites may have superior impact performance compared to their monolithic stiff phase. Here, we develop nacre-like designs using two base materials that are vastly different in properties and assemble them in a ply with an architecture similar to nacre. These plies are then stacked with orientation angles of 0 and 90 degrees to generate a laminate construct. Impact testing of three-dimensional printed (3D-printed) designs is conducted in a droptower test setup. A finite element model is created and validated with experiments to enhance our understanding of the underlying mechanisms occurring during impact. Our experimental and simulation results show that nacre-like designs outperform the constituent materials in impact resistance. This study demonstrates that emerging 3D-printing technology can enable rapid prototyping towards composite designs with optimal impact-resistant properties, suitable for the next generation of protective material systems for soldiers and vehicles.