Characterization and constitutive modeling of composite materials under static and dynamic loading

Composite materials were characterized under quasi-static and dynamic loading and a constitutive model was adapted to describe the nonlinear multi-axial behavior of the materials under varying strain rate. The materials investigated were unidirectional glass fiber/vinylester, and carbon fiber/epoxy composites. Multi-axial static and dynamic experiments were conducted using off-axis specimens to produce stress states combining transverse normal and in-plane shear stresses. Stress-strain curves were obtained for various loading orientations with respect to the fiber direction at three strain rates, quasi-static, intermediate and high strain rate. A nonlinear constitutive model is proposed to describe the rate-dependent behavior under states of stress including tensile and compressive loading. Experimental results were in good agreement with predictions of the proposed constitutive model.