Crack Closure Based Self Healing Process for Metallic Structures

Analytical Services and Materials, Inc. (AS&M) is proposing to develop and validate a process that can extend the fatigue life of and potentially self-heal existing fatigue damage of aluminum and titanium alloys. The genesis of the proposed process is research conducted at the NASA Langley Research Center that developed a low melting point coating that flows into the crack when activated. The fatigue crack growth was postulated to be reduced due to a combination of adherence of the healing material to the crack surfaces (crack bridging) and filling of the crack with the healing material (crack closure). This process was demonstrated to reduce the crack growth rate (i.e., extend fatigue life) by a factor of 2 to 4x in inert environments. The proposed Phase I program will deliver experimental evidence of a self-healing material system and a preliminary design for an integrated healing activation system. The original research will be extended to operational environments and loading conditions with the goal of developing a system by the end of Phase II that will be viable for operational testing.