| Research Abstract |
The micromechanics study on fiber reinforced composites vas made. The main ts are summarized as follows :
1. Damage and Strength Deterioration of CFRP at Space Temperature
Fracture toughness tests were carried out for a cross ply carbon/epoxy laminate at temperatures 423K, 298K and 77K. During the fracture toughness tests, acoustic emission(AE)signals were detected. As a result, it was found that the fracture toughness value, obtained as the stress intensity factor which corresponds to the onset of abrupt increase of the accumulated AE energy, is largest at temperature 298K.
Computational simulation of deformation and fracture behavior of the CFRP laminate were carried out by use of a-probabilistic fracture model. Then, the result of the computational simulation of load-displacement curve agreed well with the experimental result. The serration was explained from the viewpoint of the scattering of debond stress and pull-out length.
2. Propagation Rate of a Stress Corrosion Crack in GFRP under Acid Environments
Stress corrosion crack tests were carried out on compact tension specimens of a cross ply E-glass/epoxy laminate in acid environment. Then, it was verified that the crack propagation rate da/dt is approximately expressed against the stress intensity factor K at crack tip in the form da/dt - AK^m where A and m are constants. Next, this relationship was examined from the viewpoint of micromechanics, and the influences of concentration of acid, temperature and fiber volume fraction on the propagation rate was clarified quantitatively.
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