Thermal degradation and performance evolution mechanism of fully recyclable 3D printed continuous fiber self-reinforced composites

An innovative recycling method that does not require separation of the reinforcement and matrix is been pro-posed based on 3D printing of continuous fiber self-reinforced composites. The continuous fiber self-reinforced polyphenylene sulfide (PPS) composites were mechanically ground and directly remanufactured by screw extrusion 3D printing. The recycling procedure was accelerated and the thermal processing of the material was reduced. This recycling paradigm of self-reinforced composites with in-situ resource utilization is ideally suited to the space environment. The recycled self-reinforced composites showed no significant loss in tensile properties and even exhibited a slight increase after multiple recycling cycles owing to the melted PPS fiber in comparison with original PPS matrix. Since recycled material didn't separate the fiber from the matrix, its flexural strength and modulus increased by 34.11% and 51.81%, respectively, when compared to original PPS matrix. Molecular structure, rheological changes, and crystallization behavior were systematically investigated to elaborate the thermal degradation mechanism of recycled composites. The results obtained from systematical characterizations indicated that the recycled composites formed the cross-linking structure when subjected to multiple screw extrusion processing. The energy consumption of the screw extrusion-based 3D printing method was also con-ducted. The total energy intensity of recycling and remanufacturing processes were only about 17.9 MJ/kg. Spatial suitability, considering the advantages of self-reinforced composite recycling for space applications, were analyzed. Finally, theoretical material recovery rate of 100% for self-reinforced composites opens the prospect to reduce maintenance logistics in space. A future application scenario for fully recyclable self-reinforced composites in space was explored.