Remanufacturing and mechanical property restoration of post-used polypropylene-based composites based on in-situ impregnated 3D printing

Abstract

A remanufacturing method of post-used PP/EPDM/talc was proposed on the base of in-situ impregnated 3D printing. Continuous ramie fiber was chosen to restore mechanical properties of post-used PP/EPDM/talc. To simulate the long-term natural exposure of materials during service process, PP/EPDM/talc was subjected to accelerated aging for three different periods. Then, continuous ramie yarns with linear densities of 24 Nm/2R and 36 Nm/2R were used to restore the mechanical properties of three kinds of aged PP/EPDM/talc, respectively. For each kind of continuous ramie fiber reinforced aged PP/EPDM/talc composites, optimal printing parameter combination was obtained by response surface methodology (RSM) coupled with Box-Behnken experimental design, based on quasi-static compression tests. The dynamic compressive properties of 3D printed CFRPPCs printed with optimal printing parameter combinations were studied using split Hopkinson pressure bars (SHPB) over a wide range of strain rates and temperatures. The results showed that the quasi-static mechanical properties of post-used PP/EPDM/talc could be almost entirely restored by filling continuous ramie fiber. Besides, at 50 °C, the dynamic modulus and strength of PP/EPDM/talc aged for 4 days could be entirely restored by filling continuous ramie fiber with linear densities of 36 Nm/2R. However, with increasing aging days and decreasing temperatures, the dynamic mechanical properties of CFRPPCs decreased to below those of unaged PP/EPDM/talc although the addition of continuous fiber could partially restore the mechanical properties of post-used PP/EPDM/talc. Because aged PP/EPDM/talc in CFRPPCs was more prone to brittle failure than unaged PP/EPDM/talc at high strain rates and low temperatures due to the ductile-brittle transition of PP matrix.