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Record 50 of 381
Improved Damage Resistant Composite Materials Incorporating Shape Memory Alloys
Author and Affiliation:
Paine, Jeffrey S. N.(Paradigm, Inc., Blacksburg, VA United States)
Rogers, Craig A.(Virginia Polytechnic Inst. and State Univ., Center for Intelligent Material Systems and Structures., Blacksburg, VA United States)
Abstract: Metallic shape memory alloys (SMA) such as nitinol have unique shape recovery behavior and mechanical properties associated with a material phase change that have been used in a variety of sensing and actuation applications. Recent studies have shown that integrating nitinol-SMA actuators into composite materials increases the composite material's functionality. Hybrid composites of conventional graphite/epoxy or glass/epoxy and nitinol-SMA elements can perform functions in applications where monolithic composites perform inadequately. One such application is the use of hybrid composites to function both in load bearing and armor capacities. While monolithic composites with high strength-to-weight ratios function efficiently as loadbearing structures, because of their brittle nature, impact loading can cause significant catastrophic damage. Initial composite failure modes such as delamination and matrix cracking dissipate some impact energy, but when stress exceeds the composite's ultimate strength, fiber fracture and material perforation become dominant. One of the few methods that has been developed to reduce material perforation is hybridizing polymer matrix composites with tough kevlar or high modulus polyethynylene plies. The tough fibers increase the impact resistance and the stiffer and stronger graphite fibers carry the majority of the load. Similarly, by adding nitinol-SMA elements that absorb impact energy through the stress-induced martensitic phase transformation, the composites' impact perforation resistance can be greatly enhanced. The results of drop-weight and high velocity gas-gun impact testing of various composite materials will be presented. The results demonstrate that hybridizing composites with nitinol-SMA elements significantly increases perforation resistance compared to other traditional toughening elements. Inspection of the composite specimens at various stages of perforation by optical microscope illustrates the mechanisms by which perforation is initiated. Results suggest that the out-of-plane transverse shear properties of the composite and nitinol elements have a significant effect on the perforation resistance. Applications that can utilize the hybrid composites effectively will also be presented with the experimental studies.
Publication Date: Mar 01, 1996
Document ID:
19960047678
(Acquired Oct 23, 1996)
Accession Number: 96N33288
Subject Category: METALLIC MATERIALS
Document Type: Conference Paper
Publication Information: Proceedings of the 4th Annual Workshop: Advances in Smart Materials for Aerospace Applications; 295; (NASA-CP-10185); (SEE 19960047656)
Financial Sponsor: NASA; Hampton, VA United States
Organization Source: Paradigm, Inc.; Blacksburg, VA United States
Description: 1p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: No Copyright
NASA Terms: POLYMER MATRIX COMPOSITES; IMPACT RESISTANCE; SHAPE MEMORY ALLOYS; NITINOL ALLOYS; REINFORCING FIBERS; FIBER COMPOSITES; MARTENSITIC TRANSFORMATION; GAS GUNS; IMPACT TESTS; DESTRUCTIVE TESTS; DROP TESTS; IMPACT LOADS; KEVLAR (TRADEMARK); GRAPHITE; SHEAR PROPERTIES
Availability Source: Other Sources
Availability Notes: Abstract Only
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