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Improved impact damage resistance in adaptive shape memory alloy hybrid composite materials

Composite material impact damage tolerance and resistance are often limiting criteria when composites are considered for critical load bearing applications. Often undetectable to visual inspection, foreign object impact causes varying degrees of damage to composite structures which can initiate fatal material failures under various operating loads. This paper examines a new concept of composite material toughening by embedding small amounts of fibrous superelastic shape memory alloy (SMA) materials into brittle composite materials. In this preliminary study, a 2.8-percent volume fraction of activated (i.e. superelastic) shape memory alloy fibers were embedded within G40- 600/5245C graphite/bismaleimide to create a hybridized composite material. Impact test results show that with the SMA fibers, impact resistance of the hybrid composite materials was increased. At impact energies that perforate the standard graphite/bismaleimide, the SMA fibers stopped perforation of the hybridized composite. Preliminary results show that composite-ply delamination was reduced as much as 25 percent because of the embedded SMA fibers.