繊維強化複合材料の超音波伝ぱ速度と減衰係数に及ぼす界面はく離の影響

繊維方向に偏向したせん断波の散乱解析に基づく検討

抄録

Waves propagating in fiber-reinforced composite materials exhibit dispersion and attenuation due to wave scattering by fibers. In the present study, the overall characteristics of ultrasonic transverse waves propagating in a composite material with fiber-matrix interface debonding are examined via scattering analysis. The study is concerned with shear waves polarized parallel with unidirectionally reinforced fibers which are randomly distributed in an elastic matrix. The scattered wave generated by a single fiber embedded in an infinite matrix with various degrees of debonding is computed by two-dimensional boundary element analysis for several incidence angles of the plane waves in a wide frequency range. The results are used to determine the effective complex wave number for the composite, accounting also for statistical nature of the interface debonding. The attenuation coefficient and the phase velocity of the composite can be readily obtained from the complex wave number as a function of the frequency and a damage parameter characterizing the extent of interface debonding. Numerical illustrations are provided for a composite made of titanium alloy reinforced with silicon-carbide fibers. The dependence of the phase velocity and the attenuation coefficient on the frequency, the extent of debonding and the propagation direction is discussed in detail. The apparent decrease in effective composite density due to debonding is also explored through comparison between the static-limit velocity and the corresponding effective shear modulus.