Simplification of simulation models for open-hole tensile failure of lamina-based and fabric-based CFRP laminates was discussed in this study. Various numerical studies establishing high-fidelity simulation models have been performed in the last decade. Those models have capability to predict damage progression and strength accurately by simulating all of possible damage mechanisms strictly. However, due to their high computational cost and the complexity in modelling, those models are unsuitable for the industrial field, where the reasonable compromise between accuracy and efficiency is required. A simplified simulation model which intentionally neglects damage mechanisms which have little effect on the results is proposed in this study. Instead, a less-accurate but high-efficient damage model is used. In order to investigate the effects of the modelling method on computational accuracy and time, we conducted several numerical simulations using different damage models. The results were compared with the experiments.
The present study deals with electrical resistance change of woven-fabric CFRP during loading. Four kinds of plain weave woven-fabric CFRP laminated specimens are prepared. The specimens are subjected to cyclic tensile loading that does not cause any damages, and the electrical resistance changes of the specimens are experimentally measured by the four-probe method. As a result, the present study shows that the electrical resistance of a specimen comprising of six of ±45° plies remarkably decreases with the increase of the number of the loading cycle. The decrease is caused by the shear plastic deformation of ±45° plies. The thickness shrinkage caused by the shear plastic deformation increases the number of fiber contacts, and this decreases the interlaminar contact resistance between the plies. For single of ±45° ply, the same electrical resistance decrease caused by the shear plastic deformation of ±45° ply is observed, and the magnitude of the decrease is smaller than that of the six-ply laminate. This is because the effect of interlaminar contact resistance decrease does not exist for the single of ±45° ply. For the six of 0/90°plies, the present study shows that the electrical resistance in the through-thickness direction is decreased by the out-of-plane plastic deformation of carbon fiber and the misalignment of the plies.
Local out-of-plane deformation of CFRP ablator subjected to very rapid heating was investigated in this study. The local out-of-plane deformation is measured by three dimensional digital image correlation (3D-DIC) technique. The 3D-DIC at high temperature is achieved by high-temperature resistance random pattern on specimen surface using ceramic bond and blue filter intended for cutting strong infrared radiation from the specimen. Then discussed the mechanism of the local out-of-plane deformation only at the rapid heating condition, in terms of carbonization, pyrolysis gas occurrence, gas pressure storage and interlaminar debonding due to the gas pressure in this study.