Effect of matrix crystallinity of carbon fiber reinforced polyamide 6 on static bending properties

Recently, carbon fiber reinforced thermoplastics (CFRTP) have been widely used for various applications instead of carbon fiber reinforced thermosetting plastics (CFRP). Some matrix resins of CFRTP are crystalline polymers such as polyamide (PA), polyetheretherketone (PEEK), and polyimide. In this study, carbon fiber reinforced polyamide 6 was used, and the effect of crystal state of PA6 on the mechanical properties of CFRTP was investigated. To understand the crystal state of PA6, Differential scanning calorimetry (DSC) analysis was carried out, and an increase in the heat treatment time increased the crystallinity of PA6. The results of bending tests showed that there was a relationship between bending strength and crystallinity, however, longer heat treatment time decreased Young's modulus. The results of acoustic emission (AE) analysis and fractography showed that 30-h heat treatment made the matrix resin of CFRTP more brittle. To investigate the reason for this behavior, the DSC analysis of CFRTP was carried out. After the 30-h heat treatment, the crystal state was different compared to that of other materials. Therefore, bending properties are affected by the crystal state. Consequently, the crystal state must be considered to create CFRTP with desired properties.

Automated summary

This study investigated the effect of crystal state of polyamide 6 on the mechanical properties of carbon fiber reinforced thermoplastics (CFRTP). It was found that the bending strength was related to crystallinity, but longer heat treatment time decreased Young's modulus. Moreover, changes in crystal state made the matrix resin more brittle, highlighting the importance of considering crystal state in creating desired properties for CFRTP.