Quantification of Cohesive Properties in Bioinspired Interfaces of 3D-Printed Heterogeneous Materials

Abstract This study employs a Cohesive Zone Model to quantitatively evaluate the evolution of interfacial fracture parameters across various interface architectures. Employing the Material Extrusion (ME) type 3D printing method, sutural interfaces characterized by the interpenetration of soft and hard polymers are fabricated. The experimental framework employs a model material system comprising Polylactic Acid (PLA) as the hard phase and Thermoplastic Polyurethane (TPU) as the soft phase. Modulating a critical parameter in the ME process enables the variation of the interpenetration length of protrusions at the interface, thereby achieving a spectrum of interfacial strength and toughness. Cohesive traction-separation curves are directly derived through the double edge notch tension (DENT) test. The shape of these curves exhibits significant dependence on interface morphology, transitioning from a triangular to a trapezoidal shape as the interpenetration length increases. The numerically obtained traction-separation curves accurately reproduce the experimentally obtained counterparts. Hence, the proposed method demonstrates efficacy in successfully extracting cohesive parameters of bioinspired interfaces across a broad range of interface strength and toughness. This methodology holds promise as a characterization technique for 3D printed bioinspired interfaces in multimaterial polymer composites.