Deformation regularities of carbon fiber reinforced plastic under time variable loading

The effect of strain rate on the stress-strain deformation process of unidirectional composites was investigated. As taking into account the influence of structural and technological factors, engineering methods of identification for mechanical characteristics were created. Descripting the mechanical properties of a laminate for a given structure was usually carried out based on the regularities of its constituent layers. The analysis of the viscoelastic properties of composite materials showed that along with the manifestation of rheological properties, a physical nonlinearity was observed, which may be a consequence of shear stresses. This paper is devoted to the development of a phenomenological model of the hereditary type, which makes it possible to evaluate the anisotropy of the rheological properties of a unidirectional composite by the results of tests over a wide range of strain rates. To obtain the constitutive equations, we used the relations of the anisotropic theory of elasticity, the Volterra correspondence principle and the algebra of resolvent operators, which simplify the transformation of the equations. To derive the constitutive equations for the layer, it was assumed that the dependence of the properties on time in the reinforcement direction can be neglected. In the direction perpendicular to the reinforcement, hereditary-elastic behaviour was assumed. The comparison of calculated data and experimental results was presented. (paper)