COMPOSITE INTERFACE ANALYSIS USING VOLTAGE CONTRAST XPS

Voltage contrast x-ray photoelectron spectroscopy (XPS) was developed to characterize the interfacial bonding properties in carbon fiber-reinforced polymer matrix composites. The differing electrical properties of the fiber and matrix allow biasing of the matrix and separation of the fiber and matrix signals in the XPS spectrum. The result is a quantitative measure of the relative amount of exposed fiber and exposed matrix at tbe fracture surface of a failed composite specimen. A parameter used to describe the interfacial bonding is defined as the ratio of the areas of the carbon Is peaks from the fiber and matrix components and is referred to as the interfacial bonding ratio or C-f/C-m. Typical values of C-f/C-m for polyacrylonitrile-based carbon fiber-reinforced polymer matrix composites range from zero (excellent bonding) to three (poor bonding). The voltage contrast technique was used to demonstrate the effects of matrix resin chemistry, electrolytic oxidative fiber surface treatment, fiber processing temperature, fiber modulus and hydrothermal damage on interfacial bonding.