Improved transverse shear calculations for rate-dependent analyses of polymer matrix composites

A numerical procedure has been developed to investigate the nonlinear and strain-rate-dependent deformation response of polymer matrix composite laminated plates under high strain-rate impact loadings. A recently developed strength of materials based micromechanics model, incorporating a set of nonlinear, strain-rate-dependent constitutive equations for the polymer matrix, is extended to account for the transverse shear effects during impact. Four different assumptions of transverse shear deformation are investigated to improve the developed strain-rate-dependent micromechanics model. The validities of these assumptions are investigated using numerical and theoretical approaches. A method to determine through the thickness strain and transverse Poisson's ratio of the composite is developed. The revised micromechanics model is then implemented into a higher-order laminated plate theory that is modified to include the effects of inelastic strains. Parametric studies are conducted to investigate the mechanical response of composite plates under high strain-rate loadings. Results show that the transverse shear stresses cannot be neglected in the impact problem. A significant level of strain-rate dependency and material nonlinearity is found in the deformation response of representative composite specimens.