Fatigue and durability assessment of PA6-based carbon fiber composites for lightweight applications

Abstract

The use of lightweight structural elements across various industries has seen significant progress due to the adoption of carbon fiber-reinforced polymers (CFRPs). Among these, polyamide 6 (PA6) stands out as a prevalent thermoplastic polymer, renowned for its exceptional processability, favorable mechanical attributes, and cost-effectiveness. These qualities position it as a compelling candidate for serving as a matrix material in CFRPs. Nevertheless, as these composites find application in the development of lightweight automotive components, there arises a need for a more comprehensive comprehension of their mechanical characteristics and responses under diverse loading scenarios, encompassing fatigue behavior. So, this study investigated the mechanical behavior of CFRP based on the PA6 matrix under tensile and fatigue loading. The volumetric fractions of CF, PA6 matrix, and voids of the CF/PA6 composites were determined by acid digestion analysis, and the values of 48%, 51.6%, and 0.4%, respectively, indicated the good quality of the studied laminate. Tensile tests showed good repeatability, and the results were used to establish fatigue limits at a ratio (R) of 0.1. Fatigue tests showed that the CFRP had an infinite life of 1 million cycles at a stress level of 75%. Fractographic analysis revealed that specimens tested at lower levels of fatigue had better fracture aspects compared to those tested at higher levels. These findings contribute to the understanding of the fatigue behavior of CFRP with PA6 matrix and provide insights for their potential use in applications for lightweight structures.