A Design Tool for Robust Composite Structures

New opportunities exist for enhancing the impact resistance of organic matrix composites while simultaneously imparting multifunctionality. They draw upon the existence of organic fibers, especially Dyneema. The principal objectives of the present study were to ascertain the fundamental mechanical properties of Dyneema fibers and assess strategies for integrating these fibers into load-bearing structures. The results reveal that the tensile strength of Dyneema composites increases by a factor of 2 and the ductility by almost a factor of 3 over the strain rate range 10-3 s-1 to 104 s- 1. One consequence is that the Dyneema composites outperform by a wide margin (factor of 4) the ballistic resistance of CFRP composites at the same areal density. Moreover, it has been demonstrated that Dyneema composites can be integrated into metallic sandwich panels with either metallic prismatic cores or polymer foam cores using mechanical attachment schemes. When integrated into such structures, the full impact resistance of the composites is realized only when the backside is unconstrained at the impact site and is thus free to deform. Dyneema fibers can also be incorporated into hybrid carbon fiber composites as through-thickness reinforcements, with benefits in impact resistance and retained compressive strength.