High strain rate tensile and compressive testing of braided composite materials

Data from tension and compression tests at quasi-static and impact strain rates of up to 50s(-1) (corresponding to impact speeds of up to 7ms(-1)) are presented to characterise the effect of strain rate on mechanical properties of triaxially braided carbon/vinyl ester. Three braid architectures were studied; 0 degrees/+/- 30 degrees, 0 degrees/+/- 45 degrees and 0 degrees/ 60 degrees where the 0 degrees was an 80k tow and the +/- 30 degrees to +/- 60 degrees braid tow was 12k. The methodologies and apparatus used were developed for testing composite materials with a large unit cell size at a range of strain rates and are based on novel tensile and compressive loading rigs in conjunction with a modified instrumented falling weight machine (drop tower). In the paper, the effects of increase in strain rate on fibre and matrix dominated material properties are presented. The ultimate tensile and compressive strengths were found to vary with rate. The axial properties of the braided carbon/vinyl ester, dominated by the 80K carbon fibre tow, were relatively insensitive to rate, but strong rate dependency was seen in the transverse directions where the effects of the polymer resin were more significant.