Correlation of Fiber Composite Tensile Strength with the Ultrasonic Stress Wave Factor

An acoustic-ultrasonic technique was used to indicate the strength variations of tensile specimens of a graphite/epoxy composite. A “stress wave factor” was determined and its value was found to depend on variations of the fiber-resin bonding as well as fiber orientation. The fiber orientations studied were 0 deg (longitudinal), 10 deg (off-axis), 90 deg (transverse), [0 deg/±45 deg/0 deg] symmetrical, and [±45 deg] symmetrical. Correlations indicated that the stress wave factor can predict variations of the tensile and shear strengths of composite materials. The method was also found to be sensitive to strength variations associated with microporosity and differences in fiber/resin ratio.