An experimental investigation of the dynamic fracture behavior of 3D printed nacre-like composites.

The dynamic fracture behavior of 3D printed nacre-like composites was fully characterized by performing three-point bending dynamic fracture experiments. Nacre-like specimens with brick and mortar microstructures were fabricated with dual-material 3D printing technology. A brittle rigid material and a rubber-like material were selected for the brick layers and adhesive of the composite, respectively. First, two crack propagation paths of specimens under impact loading were observed. The dynamic behavior of the specimen under three-point bending impact loading showed a sensitivity to the impact velocity. Then, the influences of the brick aspect ratio and adhesive thickness on the fracture failure were determined. The results showed that for the case of brick aspect ratio of 1, the peak force and peak effective surface energy increase with increasing adhesive thickness, meaning that the specimen with a larger adhesive thickness had a greater bearing capacity. For the case of brick aspect ratio of 3, when the adhesive thickness was small, the nacre-like composites exhibited a lower bearing capacity than the rigid bulk material under impact loading. However, as the adhesive thickness increased, the bearing capacity and fracture toughness of the composite improved and ultimately exceeded those of the rigid bulk material. For the specimens with a small brick aspect ratio, the cracks propagated primarily along the soft adhesive, whereas for the specimens with a large brick aspect ratio, the cracks were more likely to propagate through the hard brick. Additionally, a plateau appeared in the load-displacement curves of the specimens with a large brick aspect ratio.