Models for the strain-rate-dependent behavior of polymer composites

The present study aims at characterizing the rate-dependent non-linear behavior of two polymeric composite material systems, the unidirectional S2-glass/8553-40 and the woven 7781/Fl55 E-glass fabric in the range of 0.0001 to 1/s under monotonic and proportional loading situations. The objective is to develop a viscoplasticity and a rate-dependent failure model. Uniaxial tension tests were conducted on various off-axis coupon specimens to obtain stress/strain curves for various strain rates. A three-parameter constitutive model is proposed to fit the experimental data. A single rate-dependent parameter is shown to be adequate for capturing the effect of strain rate on strength in both the unidirectional and the woven material systems.