IN-SITU SCANNING ACOUSTIC MICROSCOPY FOR DAMAGE PROGRESS CHARACTERIZATION IN THERMOPLASTIC COMPOSITES

Abstract Scanning acoustic microscopy (SAM) has proven to be an excellent technique to study the fundamental roles of constituent materials including fibers, matrix and fiber/matrix interfaces in the microfracture process of composites, because the excellent contrast between fibers and matrix can be accomplished due to the large acoustic impedance mismatch. In the present study, in-situ SAM observation technique was developed to characterize the microscopic damage progress under tensile loading in injection-molded nylon 6 matrix composites reinforced with randomly-oriented short glass fibers. Three different kinds of silane coupling agents were used to obtain composites with different static in-plane fracture toughness and drop-weight impact fracture resistance. Difference in microscopic damage progress of these three materials was investigated by the in-situ SAM technique, which revealed micro-deformation and fracture mechanisms such as, matrix plastic deformation and/or matrix microcracking, and fiber/ matrix debonding and pull-out during the loading and unloading. These quantitative microscopic characteristics were, then, successfully correlated with the macroscopic fracture properties. KEY WORDS: In Situ scanning acoustic microscopythermoplastic compositesshort glass fiberdamage progressfiber/matrix debondingplastic deformation