Abstract
Recently, carbon fiber reinforced thermoplastics (CFRTPs) have been widely used for various applications instead of carbon fiber reinforced thermosetting plastics (CFRPs). Some of the matrix resins of CFRTPs are crystalline polymers such as polyamide (PA), polyether ether ketone, and polyimide. In this study, the effect of the crystal state of carbon fiber reinforced polyamide 6 (PA6) on the mechanical properties of CFRTP was investigated. To understand the crystal state of PA6, differential scanning calorimetry (DSC) analysis was carried out. Increasing heat-treatment time increased the crystallinity of PA6. The results of bending tests show a relationship between bending strength and crystallinity; however, longer heat-treatment time decreased the Young’s modulus. The results of acoustic emission analysis and fractography show that 30 h of heat-treatment increased the brittleness of the matrix resin of CFRTP. To investigate the reason for this behavior, DSC analysis of CFRTP was carried out. Heat treatment for 30 h changed the crystal state compared with the other materials; therefore, bending properties were affected by the crystal state. Consequently, the crystal state must be considered to produce CFRTPs with the desired properties.
