超音波透過特性を用いた炭素繊維強化複合材料積層板の層間界面剛性およびプライ複素弾性率の評価

Abstract

The interlaminar interfacial stiffnesses and the ply complex elastic constants of carbon/epoxy composite laminates were evaluated nondestructively from the ultrasonic wave transmission characteristics. Using the through-transmission immersion technique, the energy transmission coefficient of longitudinal wave was measured for unidirectional, quasi-isotropic, and cross-ply composite laminates made of the same UD prepregs for various frequencies and incident directions. The results were then fitted to the theoretical ones calculated by the stiffness-matrix approach with the thin interlaminar resin-rich regions modeled as interfaces with normal and tangential springs in order to identify the interlaminar interfacial stiffnesses as well as the anisotropic viscoelastic constants of the ply constituting the laminates. The validity of the evaluation method was verified on the basis of the experimental results. The evaluated ply complex moduli were found to have comparable values irrespective of the stacking sequence of the laminate. On the other hand, the interlaminar interfacial stiffnesses were found to be smaller when the neighboring plies had the different fiber orientation angles.