Effects of fabrication processes and tape thickness on tensile properties of chopped carbon fiber tape reinforced thermoplastics

Abstract

The lack of research focused on quantifying the effects of fabrication process on the mechanical properties of carbon fiber sheet molding compounds (CF-SMCs) limited the industrial applications because the fabrication processes have a significant effect on the mechanical properties. Chopped carbon fiber tape reinforced thermoplastics (CTTs) are a novel type of CF-SMCs with outstanding mechanical performance. In this study, CTTs were molded using two fabrication processes, viz. Sheet molding (SM-CTT) and bulk molding (BM-CTT), and three tape thicknesses. The tensile tests of the specimens were conducted with in situ acoustic emission (AE) monitoring. Fractographs were also obtained for all specimens. The results indicated that fabrication processes have a prominent effect on the tensile properties of CTTs. The SM-CTTs demonstrated stable and superior mechanical performances than BM-CTTs for all tape thicknesses. The tensile properties deteriorated significantly with increase in tape thickness. The tensile moduli vary from 33.2 GPa to 42.9 GPa and tensile strengths vary from 186.2 MPa to 501.0 MPa with different fabrication processes and tape thicknesses. From the AE monitoring, the initial damages observed in BM-CTTs occurred in much earlier strain level comparing with the initial damages of SM-CTTs. Fiber breakage is the main failure mode in SM-CTTs with thin tapes, while interphase and interface debonding also observed in BM-CTTs and CTT with thick tapes. This paper addresses the lack of research on quantified effects of fabrication processes on the mechanical properties of CF-SMCs.