3D printing microlattice interpenetrating phase composites for energy absorption, damage resistance, and fracture toughness

Under external load, lightweight cellular solids are often associated with localized deformation that would lead to their catastrophic failure. Cellular solids are thus often infilled with a soft secondary material, constituting interpenetrating phase composites. Owing to highly interconnected porous architectures and controllable smooth surfaces, the triply periodic minimal surface structures based on interpenetrating phase composites are investigated in this paper. Samples are fabricated via polyjet multi-material printing, with the hard material taking on the primitive lattice and the soft material taking on its inverse. Quasi-static compression and three-point bending tests were performed on the fabricated composites. Results show that the combination of high stiffness, strength, and prolonged smooth plateau stress endows the composites to be promising for lightweight materials and energy absorbers. The designed composites can exhibit an excellent fracture toughness of 0.51 MPa center dot m1/2. Moreover, the designed interpenetrating architectures and stiff-contrast materials intrinsically control the strengthening and toughening mechanisms. The findings presented here demonstrate the potential to obtain enhanced mechanical properties by combining the advantages of the multi-material printing technique and interpenetrated design.