Modeling Heterogeneities and Elastic Anisotropy in Single Crystal Zinc and Carbon Fiber Epoxy Composites

Abstract

Laser generated ultrasound has been used to determine material properties and to characterize material defects [1–3]. To a large extent, the success of laser ultrasonics has been the researcher’s ability to correctly predict the temporal evolution of the displacement waveform resulting from pulsed laser irradiation. Theories that assume isotropic elastic properties work well for crystalline materials that have randomly oriented grains with grain sizes that are small compared to the wavelength of the interrogating ultrasonic wave [4–5]. For single crystal samples or carbon epoxy composites, the elastic anisotropic nature must be taken into account. A number of researchers have shown that the behavior of single crystal materials in the presence of an ultrasonic disturbance differ markedly from their isotropic counterparts [6–13]. Mourad et al. [6] used the Cagniard-de Hoop method [14] to numerically obtain the solutions to Lamb’s [15] problem in an anisotropic half-space. In their paper, Mourad et al. assumed that the laser source could be modeled as a shear stress dipole applied at the bounding surface. In addition, Weaver et al. [7] have studied the elastodynamic response of a thick transversely isotropic plate to a normal point source applied at the bounding surface. Of particular interest is the work by Payton [13], who has treated a general class of problems for crystals that exhibit transverse isotropy.