Influence of matrix and interface on transverse mechanical properties of CF-PEI thermoplastic composites at elevated temperatures

The influence of environmental temperature on the interface between T700S carbon fiber (CF) and a polyetherimide (PEI) thermoplastic polymer, and matrix-interface-relevant mechanical properties of a unidirectional CF-PEI composite was investigated. The single-fiber fragmentation test, and the transverse tension and flexure tests were carried out in a temperature range from ambient temperature to 130degreesC. The experimental results demonstrated that the deterioration of the transverse tensile and flexural strength of the unidirectional CF-PEI laminate was correlated with the decrease in the interfacial shear strength (IFSS) with increasing temperature, but its effects were obscured by other dominant factors such as the reduction of matrix strength. However, from the fractographic observation of the failure mechanisms, the interface-dominated failure mode at elevated temperatures confirmed its detrimental effects on the transverse strength of the CF-PEI composite.