An investigation into mechanical properties of a 3D printed two-matrix continuous fiber composites with multi-cavity structure

A continuous fiber reinforced two-matrix composites with multi-cavity structure was fabricated by a co-extrusion method, combining the excellent wettability of thermosetting resin to fiber and the wonderful extrusion forming ability of thermoplastic for nozzle based additive manufacturing (AM). Diversified component materials were utilized to enrich database for the AM of continuous fiber composites, including continuous carbon fiber (CCF), continuous basalt fiber (CBF), short fiber reinforced polyamide (SFRPA), polyamide (PA), polylactic acid (PLA) and epoxy resin. The tensile and flexural tests were conducted to investigate the effect of component materials on the mechanical properties. The micro-structures of printing filament and the fracture morphology of samples were characterized by optical microscope (OM) and scanning electron microscopy (SEM), respectively. A novel numerical model based on Peridynamics (PD) was proposed for the simulation of failure model. The three-dimensional (3D) printed continuous fiber reinforced two-matrix composites with multi-cavity structure show dissimilar mechanical behavior and failure characteristic for different combinations of component materials. The micro-structure of the fiber bundle pre-impregnated by epoxy resin after printing has a great influence on the mechanical properties and fracture modes of the samples. The failure modes mainly include pullout and breakage of fiber, stress whitening and crack of matrix, and interfacial debonding. The PD model effectively captures the tensile and flexural failure characteristic of 3D printed composites with multi-cavity structure. The results from experimental analysis and numerical simulation have reference significance for structural optimization and failure prediction of continuous fiber composites printed by co-extrusion process.