Evaluation of Interfacial Properties for Carbon Fiber/ Polyamide Model Composites by Means of Single Fiber Pull-Out Test

Abstract

Carbon fiber reinforced thermoplastics (CFRTP) have a lot of attention for their application to mass-produced-cars. While large amount of process and material data are available for carbon fiber reinforced thermoset composites (CFRP), CFRTP dose not have enough data in manufacturing process and mechanical properties compared with CFRP. Polyamide 6 (PA6) resin is expected to the matrix of CFRTP because of its low cost, good bonding to the carbon fiber, and good moldability. In order to establish design criteria and life assessment of carbon fiber reinforced PA6 resin composite, quantitative assessment of the environmental influence on the fiber/matrix interfacial strength is needed. The single fiber pull-out test was carried out to investigate the influence of water absorption on the interfacial shear strength of PAN-based carbon fiber/polyamide 6 composites. The interfacial shear strength was 38.3MPa for dry specimen, and those of one day and one week wet specimens are 22.9 and 11.3MPa, respectively. Water absorption test was carried out in distilled water at 80°C. The fiber/matrix interfacial shear strength was severely decreased by water absorption. Dry and one day wet specimens were fractured by adhesive failure with interfacial crack. For one week wet specimens, fracture morphology was divided into two groups. For most of one week wet specimens, the crack propagated in the matrix near the fiber/matrix interface. For two of them, the crack propagated in the interface. From this difference of the fracture morphology, process of water absorption to the pull-out specimen is considered as follows. The water absorbed through the interface and degraded the interfacial shear strength. Then, absorbed water diffuse to the resin and the resin was degraded.