Features of Inelastic Behavior of a Composite Under Cyclic Loading. Experimental and Theoretical Investigations

For a carbon-fiber-reinforced plastic made of an ELUR-P unidirectional tape and an ХТ-118 cold-cure binder, specimens with a ±45° stacking sequence were tested for cyclic tension. The total axial strain was considered as the sum of nonlinearly elastic, viscoelastic, and irreversible creep strains. Using the Abel creep kernel, it was found that, at instants of time shifted by values multiples of the loading period, the ratios between the viscoelastic strain components depended neither on the period of cyclic loading, nor the loading amplitude, nor the parameter determining the degree of viscosity of the material, but only on the parameter determining the decrease in the rate of the viscoelastic strain. To find parameters of the creep kernel, an identification method based on the use of a hypothesis that allows one to separate reversible and irreversible creep strains, as well as on the properties of Abel creep kernel was developed. The method is illustrated by an example of processing experimental results.