Mechanical reinforcement of additive-manufactured constructs using in situ auxiliary heating process

Abstract

The material extrusion (ME) process, which is an additive manufacturing technology applicable to a wide range of polymers, has a drawback in that the inherent bonding between the deposited layers is vulnerable. To this end, we present an efficient strengthening method for the ME process by introducing bidirectional in situ infrared (IR) heating during the polymer melt deposition in the 3D-printing process. The auxiliary IR irradiation was applied to heat as-printed polymers in the deposited area along the printing paths at their glass transition temperature, which expectedly led to molecular diffusion and chain re-entanglement at the deposited interface. Consequently, the heating technique not only helped eliminate the structural defects due to the thermal stress but also helped enhance the mechanical strength, particularly of structures layered in transverse and upright directions. The reinforcement effects were confirmed by conducting tensile tests and thermal imaging analysis on typical polymers such as polylactic acid and polycarbonate. The experimental results demonstrated the feasibility of the proposed heating technique in extending the applicability of a wide range of engineering plastics or composite materials for the ME printing method.