炭素繊維／ポリイミド樹脂複合材料の熱サイクルによるマイクロクラック発生と圧縮強度低下

Abstract

The objective of this study was to investigate the effect of thermal cycles, encountered by an Super Sonic Transport (SST) in service, on the cumulative frequency of microcracks and the degradation of compressive strength in carbon fiber/polyimide resin composite materials.One thermal cycle was designated as a sequence from room temperature (RT) to -54°C, and then to +177°C, finally back to RT. Transverse microcracks initiated on the sectional free edge surface of the laminates were observed and counted by using an optical microscope. Approximate 10000 thermal cycles were given for five kinds of carbon fiber/polyimide composite material: IM7/PIRA, IM600/PIXA-M, IM600/PIXA-MT3, IM7/K3B, IM7/R1-16, as well as a Ti/Gr (polyimide CFRP) fiber metal laminate. For IM7/R1-16 thermal cycling tests were conducted up to 40000 cycles.Transverse microcracks were observed not only on the sectional free edge surface but also on the inside cross section of specimens cut after thermal cycling tests for IM7/R1-16. Static open-hole-compressive (OHC) strength was measured at RT before and after thermal cycling tests on the five kinds of material except for IM7/PETI-5. Static nonhole-compressive (NHC) strength was measured at RT on IM600/PIXA-M and IM600/PIXA-MT3. In addition, in order to know the estimates of thermal stress generated by the thermal cycles, the thermal stresses were calculated by the classical lamination theory (CLT) using basic lamina data given in a reference.