Effect of crystallinity on the mechanical behavior of carbon fiber reinforced polyethylene-terephthalate (CF/PET) composites considering temperature conditions

ABSTRACT Thermoplastic differs in crystallinity depending on the manufacturing conditions such as temperature and cooling rate, which affect the mechanical properties of the thermoplastic-based composites. In this work, the crystallinity of polyethylene terephthalate (PET) was varied according to the cooling rate to investigate the mechanical properties of PET matrix-based carbon fiber (CF)/PET composites. The thermal characteristics and crystallinity were analyzed through the differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis. The mechanical behavior of CF/PET composites with different degrees of crystallinity was studied with varied temperature conditions. The failure modes of the fractured CF/PET composites were observed by using a digital microscope and scanning electron microscope (SEM). As a result, the crystallized CF/PET composites were improved 11.6 times higher in in-plane shear (±45° laminated) strength and 3.78 times higher in shear modulus than that of amorphous CF/PET composites at high temperature.