J046033 マイクロ波伝播理論による繊維強化複合材料内部の層間はく離の定量評価(〔J046-03〕高分子基複合材料の加工と評価(3))

Abstract

Glass fiber reinforced plastic (GFRP) is lightweight, inexpensive and high corrosion-resistance material. So, GFRP is used for the structural members such as aircrafts, ships and the blades of electric-generating windmills. However, GFRP is often generated delamination under service environment. Moreover, the delamination causes extreme reduction of compressive strength of the material. Thus, the nondestructive inspection method to detect delamination in GFRP is required. Ultrasonic inspection, infrared thermography and radiography have been studied to detect delamination. However, these inspection methods cannot evaluate the thickness of delamination whereas it is very important to evaluate the seriousness on strength. For the reason, in this study, we attempted to evaluate the thickness of delamination in GFRP by microwave inspection method. The method can evaluate the thickness of delamination in GFRP because microwave reflected from GFRP is changed by the thickness of internal delamination. In this paper, a theoretical model to derive reflectivity of GFRP having internal delamination was developed. Subsequently, the thickness of polyethylene film inserted in GFRP instead of delamination was evaluated from the comparison of a theoretical reflectivity and a calibrated experimental reflectivity. As the result, the potential of microwave inspection to evaluate a thickness of delamination in GFRP was presented.