An experimental-numerical technique for evaluating the elastic constants of unidirectional laminates by the optoacoustic method:: Comparison with some theoretical results

In the present article, the elastic constants for unidirectional transversely isotropic laminated composites are measured using the optoacoustic method. In this method, a laser pulse is used as a standard source of ultrasound. Different three-layer unidirectional laminated specimens with different volume fractions of reinforced graphite 716, Kevlar KS-400, and S-2 glass fibers were prepared. The engineering elastic constants (E-1, E-2, G(12),nu(12)) were obtained by means of the longitudinal velocity measured indifferent directions and then fitted in the stress-strain relations for a lamina that is stressed in nonprincipal x-y coordinates. The elastic constants determined with the experimental-numerical technique were compared to different theoretical models reported in the literature, such as Hill's modified model, Hashin and Hashin-Rosen's upper and lower bounds models, and the asymptotic homogenization method. The experimental results obtained in this work show good agreement with those mentioned above.