NITINOL-REINFORCED PLATES .1. THERMAL-CHARACTERISTICS

The static and dynamic characteristics of NITINOL-reinforced composite plates are influenced primarily by the temperature distribution insid e the composite matrix. Such distribution arises from the electrical h eating of NITINOL fibers embedded along the neutral plane of these com posite plates. When temperatures are developed above the martensite tr ansformation temperature of the NITINOL fiber, the elastic modulus of the fibers increases approximately fourfold and significant phase reco very forces are generated. Such thermal activation of the NITINOL fibe rs increases the elastic energy of the fibers and enchances the stiffn ess of the plates, provided that the phase recovery forces are high en ough to compensate for the loss of the modulus of elasticity of the co mposite and counterbalance the generated thermal loads. Understanding the interaction between the thermal, static and dynamic characteristic s of the NITINOL-reinforced plates is essential to tailoring the perfo rmance of these plates to match changes in the operating conditions. S uch an interaction is influenced primarily by the temperature distribu tion inside the plates during the activation and de-activation of the NITINOL fibers. In this study, a thermal finite element model is devel oped to determine steady-state and transient temperature distributions inside NITINOL-reinforced composite plates resulting from different a ctivation strategies of the NITINOL fibers. The theoretical prediction s are compared with experimental measurements in order to validate the thermal finite element model. The resulting temperature distribution can be used to determine an average modulus of elasticity of the compo site. The average temperature rise above ambient can also be used to c ompute the axial thermal loading on the composite plate. Such predicti ons are utilized in computing the static and dynamic characteristics o f NITINOL-reinforced plates which are presented in Parts II and III of this paper, respectively.