The Dynamic Stretch Performance Of Three Dimension Braided Composite

The article introduced the dynamic stretch test of three dimension braided composite materials including the specimen manufacture craft, the equipment and the conclusions.In order to guarantee the experiment smoothly carries on and reduces the error, we improved the test specimen manufacture craft. We take two added strengthened resin on the original test specimen. This has obtained the very good result.We have used the graph and the formula to explain the structure, principle and hardwire of SHTB, presented the form and transmittal of stretch-unloads wave. We have gained the stress-time curve, strain-time, strainrate-time and other curves at various strain rates (from 0.001 to 2100/s). Compared with the quasi-static's stress-strain curve, These results indicate that the stress strain curves are rate sensitive, and tensile modulus, maximum tensile stress and corresponding tensile strain are also sensitive to the strain rate. The tensile modulus, maximum tensile stress of the 3-D braided fabric composites is linearly increased with the strain rate.With increasing of the strain rate (from 0.001 to 2100/s), the tensile failure of the 3-D braided composite specimens has a tendency of transition from ductile failure to brittle failure.The box-counting method is a convenient method to gain the fractal dimensions of tension failure curves at various strain rates. We find that the fractal dimension of low strain rate is much bigger than that of high strain rate. This shows the stretch break mechanism of low strain rate is different with that of high strain rate. The low strain rate's break curve is much more complex and occupies more space.We analysis the characteristic of stress signal during frequency area through the method of FFT and wavelet transform, the result indicates that the energy of different frequency band is different, the low frequency band occupies much more energy than highfrequency does.