WATER DIFFUSION BASED NON-DESTRUCTIVE EVALUATION (NDE) OF PMR-II-50/M60J 4-HS WEAVE CARBON FABRIC COMPOSITE MATERIALS UNDER STRESS-THERMAL CYCLING

摘要

Due to the geometric complexity of woven fabric composite materials, conventional Non-Destructive Evaluation (NDE) methods such as x-radiography and acoustic emission (AE) do not show microcracks well inside the materials. In this study, a simple and cost effective water uptake test as a NDE methodology for PMR-II-50/M60J (polyimide/carbon fiber) 4HS weave fabric composites is suggested. The short term water uptake test for 24 hours at 80℃ has been performed before and after stress-thermal cycling experiments with the TAMU developed conduction heated stress-thermal cycling apparatus. The woven composite materials' non-Fickian model during short term water uptake, that is, the rate of uptake initially increases rapidly followed by quick slow down associated with diffusion in cure-induced voids and cracks was modified by the effective diffusivity depending on crack densities. The suggested crack densities dependent diffusion model was compared with the experimental data. The application of the water absorption induced NDE was also re-evaluated by comparing to the results of the literatures in terms of crack closure by swelling and unloading of the existing load and matrix dissolution by hot water.