Fernati P. Nonlinear creep of viscoelastic one-directional fibrous composites and their components under tension

The Thesis is devoted to the derivation and experimental justification of a nonlinear creep model of hereditary type for isotropic viscoelastic materials and to the solution of the prediction problem of creep strains of one-dimensional fibrous composites and their components as well as of creep strains of composites using component characteristics. A nonlinear creep model of hereditary type allowing to describe all typical creep process stages of linear and nonlinear viscoelastoplastic materials has been derived. A technique has been developed and domains of linearity and nonlinearity of deformation of some reinforced fibres, binders, and composites have been determined. The hypothesis of a unified isochronous deformation diagram has been justified experimentally. The technique of the material constants identification involving the choice of the structure of a heredity kernel and the determination of kernel parameters has been developed. New mechanical effects related to the creep character dependenceof the momentary deformation character have been emerged. The problems of the creep strains prediction of organic fibres, epoxide binders, and composites under loading and full unloading as well as creep of composites using components behaviour in tension along the reinforcement direction have been solved.