Inducing Retained Compressive Stresses for the Design of Lightweight Tough Composite Material Structures

"The SMA reinforced aluminum composites show self-strengthening by compressive stresses in Al matrix due to shape memory shrinkages of the embedded TiNi fibers (Furuya, 1996). The increases in tensile properties such as yield stress as well as fatigueresistance (crack growth retardation) at higher temperature were experimentally confirmed by Furuya (1996).Based on the new requirements for Future Combat Systems (FCS), there is a great need to develop MMCs with(1) minimal machining and joining requirements (near net-shape capability),(2) complex shape manufacturability,(3) improved fracture toughness (KIC) and impact toughness (Charpy)over 75% that of hardened 4340 steel, and(4) a density that is 25% lighter than steel.In Phase I of this SBIR program, our team will investigate the feasibility of using SMAs to make Al MMC with SiC particulates and/or whiskers to develop tough and durable MMCs with a manufacturing process that is capable of making complex structuralparts for application in FCS. SMA based aluminum MMC offer self-induced compressive residual stresses which willincrease the durability and damage telerance of MMC for application in demandingArmy vehicle applications such as in Future Combat Systems (FCS). Processing routesproposed can be used to develop materials in various forms allowing maximumflexibility and increasing the possibility of applications of SMA based MMCsin various structural parts. The process technology c