Resistance to delamination of 3D woven textile composites evaluated using End Notch Flexure (ENF) tests: Experimental results

The flexural response of 3D woven textile composite panels containing an edge crack is evaluated using the End Notch Flexure (ENF) test. In doing so, the effectiveness of 3D reinforcement in increasing and/or eliminating delamination is demonstrated. Two types of textile architectures, referred to as Z-fiber reinforcement and a layer-to-layer architecture were examined. At quasi-static and low rate; 0.01 mm/Section (0.0004 in/s) and 50.8 mm/Section (2 in/s), results showed that the Z-fiber reinforcement provided a higher strength, although the layer-to-layer reinforcement provided more energy absorption and prevented mode II crack propagation, thus providing insight into eliminating the delamination mode of failure. At higher loading rates, using an instrumented drop tower at impactor velocities of 2.79 m/Section (110 in/s) and 3.96 m/Section (156 in/s), results suggested a rate dependent mode II strength of the material. Computational models to further explore the experimental results are presented in a follow-on paper in this issue of the journal [1].