A novel model to predict the stiffness and strength of unidirectional glass/epoxy composites at different strain rates

Abstract

In the present research, a novel rate-dependent micromechanical model was presented to predict the stiffness and strength of unidirectional glass/epoxy composites. To predict the strain-rate dependent stress–strain behavior of glass fibers, using the Maxwell model with the aid of semi-empirical relations, a new viscoelastic constitutive model was proposed. Moreover, to predict the strain-rate dependent ultimate strength of brittle glass fibers, the elasto-plastic strain-rate dependent Cowper-Symonds material model was simplified by deleting the plastic terms. The strain-rate dependent mechanical properties of the polymer were also investigated by using the modified Goldberg model. Then, by modifying the Mori-Tanaka micromechanical model, a rate dependent micromechanical model was developed to predict the effective elastic properties (stiffness and strength) of unidirectional fibrous composites at arbitrary strain rates. The present model was called the strain-rate dependent Mori-Tanaka micromechanical model. As inputs, the present model just needs the viscoelastic and viscoplastic properties of fibers and polymer. Therefore, the present model reduces the necessary experimental data to predict the rate-dependent mechanical properties of unidirectional composites. For verification of the present model, the results were compared with experimental data and very good consistency in predicting the rate-dependent behavior of unidirectional composites was observed.