Evaluation of the Fiberglass-Reinforced Plastics Interfacial Behavior by using Ultrasonic Wave Propagation Method

In this paper, ultrasonic wave propagation in three phases (3P) of composite materials was investigated. The simulation was conducted by PZFlex analysis code, a time domain finite element program. The reflection and transmission characteristics with different shapes of middle layer between glass fiber and epoxy resin are investigated in order to understand basic ultrasonic behavior of energy dispersion and transmission in the middle layer. The relationship between impedance in middle layer and ultrasonic propagation characteristics is discussed. As a practical approach to the practical composite materials, the SFC (single fiber composite) model is proposed with a middle layer between fiber and matrix. Moreover, the influence of the middle layer with different debonding failure regions and failure directions is taken into account. As a result, the influence of the fiber/matrix interface, the geometrical size of middle layer and its physical property on wave propagation was clarified. When the debonding failure existed in the middle layer between fiber and matrix, its influence on ultrasonic motion pattern and the characteristics of energy propagation were understood. The complicated propagation behavior resulted from reflection, transmission, multi-reflection and dispersion due to the existence of debonding failure at the fiber/matrix interface was visualized. With these results, it is indicated that an approach based on ultrasonic technology is possible for the evaluation of interfacial behavior in 3P composite materials with a middle layer existed between fiber and matrix. With these results, it is indicated that an approach to the evaluation of interfacial behavior in 3P composite materials is possible.