Fatigue life prediction for off-axis unidirectional carbon fiber reinforced thermoplastic specimens, considering the high hydrostatic pressure condition of the resin

In this study, the effectiveness of fatigue life prediction using Interfacial Plastic Strain Energy (IPSE) was investigated for off-axis unidirectional Carbon Fiber Reinforced Thermoplastic (CFRTP) specimens composed of PA6, a thermoplastic resin. Given the high hydrostatic pressure experienced by PA6 within the CFRTP, we employed the Drucker-Prager yield criterion. The internal friction angle of PA6, a key Drucker-Prager parameter, was determined to be 23.8 degrees through uniaxial tensile and compressive tests, and was found to be suitable for analysis under high hydrostatic pressure conditions. Utilizing this friction angle, the IPSE of PA6 within the CFRTP was calculated via two-scale analysis. Our findings indicate that the use of IPSE enables accurate prediction of the fatigue life of CFRTP, based on the fatigue test results of pure PA6. This research provides valuable insights for the future design and utilization of CFRTP materials.