Manufacturing of Adaptive Graphite/Epoxy Structures with Embedded Nitinol Wires

Abstract

Shape memory alloy (SMA) composites are a class of smart materials in which embedded nitinol wires are used as actuators. Previous research in SMA composites has been limited to wires using one-way shape memory behavior. The objective of this paper is to assess the feasibility of using two-way shape memory (TWSM) training of nitinol, a nickel-titanium SMA, wires for their use as embedded actuators in SMA composites and to investigate the effects of processing conditions on SMA composite quality and actuation ability. Training of the TWSM behavior in nitinol was investigated for a range of initial strains and training cycles. In each case, over 50% of the initial strain can be recovered after training and trained response is generally stable after about 30 training cycles. SMA composite specimens were manufactured using either hot press or autoclave methods and several different types of cure cycles. Voids were found to congregate near the embedded wire surface and can typically be as high as 10% in these regions. Using a staged-cure cycle, the average void content was reduced to 1.3-1.5%. The effect of the composite cure cycle was found to have no significant effect on trained nitinol wire behavior. Finally, the structural behavior of an SMA composite beam was investigated by actuating wires through electrical resistance heating. The tip deflection of a cantilevered beam was found to be primarily composed of SMA transformational effects, however, some localized heating was evident.

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References

Baz, A. , K. Imam and J. McCoy . 1990. "Active Vibration Control of Flexible Beams Using Shape Memory Actuators", Journal of Sound and Vibration, 140(3):437-456.

Baz, A. and J. Ro. 1992. "Thermo-Dynamic Characteristics of Nitinol Reinforced Composite Beams", Composites Engineering, 2(5-7): 527-542.

Chaudry, Z. and C. A. Rogers . 1991. "Response of Composite Beams to an Internal Actuator Force", Proceedings of the 32nd Structures, Structural Dynamics and Materials Conference, AIAA-91-1166-CP, pp. 186-193.

Ditman, J. , S. R. White and L. Bergman . 1991. "Tensile Testing of Nitinol Wire", Technical Report UILU ENG 91-0508, University of Illinois, Urbana, IL.

Escher, K. , A. H. Exner , E. Hornbogen and H. Schmidt . 1990. "The Two Way Shape Memory Effect for Mechanical Hands", Proceedings, 31st SDM Conference, Paper AIAA-90-1028-CP (April 1990): Long Beach, CA, pp. 29-37.

Ghiorse, S. R. 1993. "Effect of Void Content on the Mechanical Properties of Carbon/Epoxy Laminates", SAMPE Quarterly, 24(2):54-59.

Liang, C. , J. Jia and C. A. Rogers . 1989. "Behavior of Shape Memory Alloy Reinforced Composite Plates Part II: Results", Proceedings of the 30th Structures, Structural Dynamics and Materials Conference, AIAA89-1331-CP, pp. 1504-1513.

Paine, J. S. N. and C. A. Rogers . 1991. "The Effect of Thermoplastic Composite Processing on the Performance of Embedded Nitinol Actuators", Journal of Thermoplastic Composite Materials, 4(2):102-122.

Rogers, C. A. and D. K. Barker . 1990a. "Experimental Studies of Active Strain Energy Hibning of Adaptive Composites", Proceedings of the 31st Structures, Structural Dynamics and Materials Conference, AIAA-901086-CP, pp. 2234-2241.

10.

Rogers, C. A. 1990b. "Active Vibration and Structural Acoustic Control of Shape Memory Alloy Hybrid Composites: Experimental Results", Journal of the Acoustical Society of America, 88(6):2803-2811.

11.

White, S. R. and Y Kim . 1992. "The Effects of Stage Curing on Mechanical Properties of Thermosetting Matrix Composites", Proceedings of the ASC Seventh Technical Conference on Composite Materials, (October 13-15):University Park, PA, pp. 69-79.