THERMO-ACOUSTIC EMISSION MEASUREMENT TO DETECT THERMALLY INDUCED MICROCRACKING IN FRP, FRM AND FRC

Abstract Thermo-acoustic emission measurement which detects thermal cracking in the composites under a thermal cycle was applied to the sheet molding compound (FRP), partially reinforced aluminum composite component (FRM) and SiC whisker reinforced alumina composites (FRC). The following results were obtained: (1) The thermal microcrackmg in FRP decreased with the increase of the fiber sizing which generates the interphase between the fiber and matrix. (2) The microcracking in FRM occurred in the portion of the reinforcement, which strongly depended on the type of the carbon fiber used for the reinforcement. (3) The microcracking in FRC was presumed to occur in cooling period of thermal cycle heating up to 600 °C, which was predicted by a stress analysis. From these results the thermo-acoustic emission is considered to be useful as a characterizing method as well as quality assurance one for the composite materials.