Dynamic compressive strengths of polymeric composites

The dynamic compressive strength of unidirectional fiber composites in the form of fiber microbuckling was investigated and modeled. Both strain rate and shear stress effects on the compressive strength were considered. The present model was developed from extending Rosen's fiber buckling model in conjunction with a viscoplasticity model to describe the inelastic and rate dependent behavior of the composite. Off-axis S2/8552 glass/epoxy composite specimens were tested at various strain rates to provide the experimental data with the presence of shear stresses. For strain rates below 1 s(-1), compression tests were conducted on an NITS loading machine, while higher strain rate tests were performed using a split Hopkinson pressure bar (SHPB). Comparison of model predictions with experimental data showed that the dynamic microbuckling model was quite accurate in predicting compressive failure of unidirectional composites for strain rates up to 900 s(-1). From the model predictions and experimental data, it was found that the presence of shear stress can significantly lower the compressive strength of composites. Comparison of the present microbuckling model and the kink band model was made. (C) 2003 Elsevier Ltd. All rights reserved.