Thermomechanical behavior of TiNi shape memory alloy fiber reinforced 6061 aluminum matrix composite
- PDF / 1,169,245 Bytes
- 9 Pages / 612 x 792 pts (letter) Page_size
- 105 Downloads / 219 Views
I.
INTRODUCTION
SMART composites that utilize shape memory alloy (SMA) fibers as reinforcement have been designed and successfully developed.[1–5] The design concept of smart composite is shown in Figure 1. The SMA fibers are loaded at room temperature transforming the austenitic phase to the martensitic phase. Then they are heated to induce the reverse transformation. The SMA fibers in a composite shrink during this reverse transformation, which induces tensile stress in fibers and compressive stress in the matrix. This compressive stress in the matrix is a key factor that enhances the tensile properties of a smart composite. The internal stress analysis is the critical step for precise evaluation of the smart composite. Recently, we developed two types of smart composite utilizing TiNi fiber as a reinforcement, namely, TiNi/Al and TiNi/epoxy. We succeeded in improving both the yield stress of TiNi/Al and the fracture toughness of TiNi/epoxy at high temperatures.[1,3,5] We used a pure Al for the composite matrix as it can be processed easily.[3] However, a pure Al matrix is not ideal for applications of smart composites to structural composites due to its low yield stress. Hence, the present study uses a 6061 Al alloy in its T6 heat treatment. In addition, we use a vacuum hot press method to enhance strong interfacial bonding between TiNi fibers and matrix for the present processing, while pressure casting of molten Al matrix was used in the previous experiments.[3] Our previous model predicted that the martensite phase induced in prestrain process shows reverse transformation K. HAMADA, formerly Research Associate, Department of Mechanical Engineering, University of Washington, is currently Research Associate, Department of Dental Eng., School of Dentistry, Tokushima University, Tokushima-City, 770-8504, Japan. M. TAYA, Professor, Department of Mechanical Engineering, and K. INOUE, Professor, Department of Materials Science and Engineering, are with the University of Washington, Seattle, WA 98195. J.H. LEE, Professor, Department of Metallurgical Engineering, Dong-A University, Pusan 604-714, Korea, is Visiting Professor, Department of Materials Science and Engineering, University of Washington. K. MIZUUCHI is Senior Researcher with the Osaka Municipal Technical Research Institute, Osaka 536, Japan. Manuscript submitted February 18, 1997. METALLURGICAL AND MATERIALS TRANSACTIONS A
to austenite above Af at high temperature, leaving the TiNi fiber fully austenite.[1] In this article, we develop a model that includes the stress effects on the phase transformation during the heating process, because the phase transformation is strongly affected by both temperature and stress.[6] Boyd and Lagoudas[2] analyzed the elastic behavior of a TiNi/elastomer composite utilizing the Mori–Tanaka micromechanics method[7] and one-dimensional model of SMA transformation.[8] However, these researchers did not compare predicted values to experimental results. Armstrong and Kino[9] and Armstrong[10] reported predictions and experime
Data Loading...
