Recycled carbon fiber reinforced polylactic acid composites for thermally recoverable 4D-printed structures

Abstract

ABSTRACT To enhance the mechanical and shape memory properties of shape memory polymers (SMPs), recycled carbon fibers (rCFs) were incorporated into the polylactic acid (PLA) matrix. The effects of rCF content on the thermal actuation, shape memory and mechanical properties of the rCF/PLA composites were investigated, and 4D-printed functional components were prepared. The results indicate that rCFs construct effective thermal pathways and load-bearing frameworks within the matrix. The 10 wt% rCF/PLA composites exhibited the optimal balance between mechanical and shape memory properties, with a porosity of only 4.18%. Compared with pure PLA, the tensile strength and modulus of the 10 wt% rCF/PLA composites increased by 55.3% and 76.7%, respectively, while its flexural strength and modulus increased by 24.3% and 77.0%, respectively. The initial shape recovery ratio increased from 90.3% to 95.4%, and the composites exhibited more stable recovery performance within the activation temperature range of 60–85°C. Notably, after 10 thermo-mechanical cycles, the 10 wt% rCF/PLA composites maintained a shape fixity ratio above 98% and a shape recovery ratio exceeding 70%. This investigation presents a sustainable strategy for high-value reuse of rCF while revealing the synergistic effects between mechanical and shape memory properties.