Single fiber pull-out investigation at different temperature and humidity conditions: Experimental characterization of the fiber-matrix interface in carbon fiber reinforced polyamide 6

This study investigates the effects of varying environmental conditions on the interfacial properties of carbon fiber-reinforced polyamide 6 (CF-PA6). The primary focus is the impact of temperature and humidity on the Interfacial Shear Strength (IFSS), debonding fracture toughness, and surface-specific work of friction. The study reveals that caused by polymer swelling both temperature and humidity lead to a relaxation of the radial residual stress within the interface and a subsequent reduction in IFSS. Notably, the effects of these factors appear to be superimposed up to the debonding of the fiber-matrix interface. Furthermore, while the debonding fracture toughness also follows a declining trend with an increase in both environmental factors, it displays non-linear characteristics, implying a coupled effect between temperature and humidity. The study also identifies that humidity alone significantly decreases the surface-specific work of friction, irrespective of the surrounding temperature, so that after debonding a simple superposition is not feasible. To ensure precise results, a microscale climate chamber was developed using the principle of deliquescence to maintain a constant relative humidity during testing. The findings offer valuable insights into the performance of CF-PA6 under varying environmental conditions, informing potential improvements in its design and application.