Design of a Biomimetic Self-Healing Alloy Composite

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Novel self-healing alloy composites have been designed to address the need for self-repairable high-strength structural materials. A systems-based materials design approach using computational design tools was used to design a multifunctional biomimetic composite that can repair structural damage. The self-healing composite consists of a controlled-melting alloy matrix reinforced by thermodynamically compatible shape memory alloy (SMA) wires. When heat is applied to the composite after damage, the embedded SMA wires apply a compressive force which produces crack closure and clamping. The matrix alloy is designed to become partially molten at the healing temperature to reverse damage induced plasticity and provide crack welding. Feasibility tests on Sn-based proof-of-concept self-healing alloy composites reinforced with 1% volume fraction of commercial Ti - 49.4 at% Ni SMA wires show a 73% increase in uniform ductility and greater than 94% recovery of ultimate tensile strength after crack healing. In an effort to design a high specific strength self-healing alloy composite, solution-treated Mg - 5.7 at% Zn - 2.7 at% Al proof-of-concept self-healing alloy composites reinforced with 1% volume fraction of commercial Ti - 49.4 at% Ni SMA wires were designed and demonstrated a 160% increase in uniform ductility. A strength model was developed, incorporating solution and precipitation strengthening mechanisms to design an aged Mg-based matrix alloy that demonstrates a strength of 192 MPa. Both the solutionized and aged alloys demonstrate greater than 40% increase in strength as compared to the commercial cast magnesium AZ91 alloy. To address issues related to increased matrix strength and the recovery capabilities of the SMA wires, a thermomechanical model was developed to predict the minimum volume fraction of wires needed for self-healing. Finally, processing effects on the SMA wire reinforcement are evaluated to design a composite that is thermodynamically compatible during processing and service. The integration of materials design methodologies within a systems engineering framework is a novel approach to the accelerated development of complex materials. In the end, an engineering material can be designed with multifunctionalities ranging from the macro- to nano-scale to optimize performance while minimizing time and the need for extensive experimentation.

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  • 07/25/2018
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