A tensile impact apparatus for characterization of fibrous composites at high strain rates

摘要

A high rate tensile testing apparatus called "flying wedge" for testing fibrous composites at strain rates up to 10~3 s~(-1) has been described.R2000 glass/epoxy composite has been tested at a very low strain rate of 10~3 s~(-1) using the universal Instron tensile testing machine, and at high strain rates up to nearly 850s~(-1) using flying wedge. The results show significant increase in failure stress and reduction in failure strain for dynamic tests with respect to quasi-static experiments. While the reduction in failure strain fluctuates from 60 to 75 percent. the increase in failure strength varies from 300 to even 500 percent for different ply angles. Although, the results may be affected by the stress waves, which propagate through the parts of the testing machine on the impact, it is found that the stress wave's effects do not play a determinant role in this regard. The results indicate that the rate of the increase of stress versus strain rate slows down as ply angle increases. Scanning electron microscopy of the fracture surface of the specimens did not reveal significant difference between the failure mechanisms at low and high strain rates.