Mode I/II cracking behavior of additively manufactured interpenetrating phase composites (IPC), an experimental and theoretical study

An interpenetrating phase composite (IPC) material combines the advantages of being made from materials for an intended behavior. 3D-printed parts have received attention for rapid prototyping of complex structures; however, their porous inherent makes them susceptible to cracking. Polymer adhesives can be used to overcome these issues to increase their strength and durability. In this paper, IPCs were developed using 3D-printed scaffolds and epoxy resin matrix, and their fracture behavior was examined. The samples were printed with 25, 50, 75, and 100 infill percentages and tested in the full range of mode I-II fracture. From the results, the promising behavior of IPCs can be seen. Where the 3d printed samples with 100, 75, 50, and 25 infills show 2.4, 1.8, 0.8, and 0.3 MPa√m mode-I fracture toughness, IPCs made from samples with 75, 50, and 25 infills, show 2.0, 2.2 and 2.7 MPa√m, respectively. The same trends are also seen in the full range of mode I-II fractures. The generalized maximum tangential stress (GMTS) criterion accurately predicted KIIc/KIc ratios among the investigated mixed-mode fracture criteria. The evaluations indicated that the discrepancy between the measurements is mainly due to the sign and magnitude of the T-stress parameter.