Composites reinforced with 3D woven fiber preforms are known to display improved through thickness performance when tested using methods such as the ASTM D6415 curved beam protocol. The presence of reinforcing fiber in the through-thickness direction eliminates delamination as a mode of failure and allows the composite to continue to carry increasing loads well beyond first crack initiation.
We propose that this characteristic of 3D woven composites may be exploited for applications such as automotive crash structures, which are required to dissipate large amounts of energy during an impact event. The rate dependent nature of these materials, however, is not well understood.
An empirical study was conducted to provide an initial understanding of the dynamic behavior of 3D composites. This study utilized sinewave cross section test elements that were crushed at several different velocities to obtain relative specific energy absorption (SEA) measures for various 2D laminate and 3D composite configurations.
In general, 3D composites were found to have higher SEA measures than 2D laminates, and orthogonal fiber architectures were found to have higher values than ply-to-ply interlocking configurations. All specimens tested displayed substantially reduced SEA for higher velocity impacts.