16 TH INTERNATIONAL CONFERENCE ON COMPOSITE MATERIALS 1 Abstract Maintaining the shape of high-precision structures such as space antennas is a challenging issue for designers. Varying temperature conditions will induce thermal distortions in these structures. Development of smart materials offers great potential to correct the shape. In this study, shape control of a composite structure under thermal loading using piezocomposites is investigated. Macro-Fibre Composite (MFC TM ) patches are bonded to the structure. The structure is subjected to a through-the-thickness temperature gradient which induces thermal distortion. The objective is to apply electric potential to the MFC actuators such that the out-of-plane deflection can be minimized. Finite- element analyses are conducted using the commercial software ABAQUS. Experiments are performed to study piezoelectric actuation, thermally-induced distortion, and compensation of thermal distortion using the MFC actuators. A control loop based on strain measurements is used to actively control the structure. Results show that MFC actuators can compensate thermal distortion and that is an efficient methodology. 1 Introduction Maintaining the shape of high-precision structures such as space antennas and optical mirrors is still a challenging issue for designers. These structures are subjected to varying temperature conditions which often induce thermal distortions. The development of smart materials and structures offer great potential to correct the shape and to minimize surface error. As a result, research in this area has been very active over the past decade. So far, piezoceramic materials have been the most widely used smart material to control the shape of a structure. Koconis, Kollar, and Springer [1, 2] were among the first ones to investigate the change in shape of composite beams, plates and shells by embedded piezoelectric actuators. Studies on determining the optimal length, actuator locations and applied voltage have been reported by Agrawal and Treanor [3], Bruch et al. [4], Sun and Tong [5] and different optimization techniques have been proposed. Thermal deformation compensation has also received considerable attention in recent years. Several coupled thermal-piezoelectric-mechanical models have been developed. For example, Ashida and Tauchert [6] proposed a general solution procedure for the analysis of composite circular plates subjected to thermal loading and piezoelectric actuation. Tan [7] developed a simulation procedure using a co-located sensing and actuating scheme based on strain measurements and applied it to compensate thermal deformation of a paraboloid shell of revolution. Song, Zhou and Binienda [8] performed finite-element analyses and experiments to investigate the compensation of thermal distortion in a composite beam. Unfortunately, the experimental results on shape control are not compared with finite-element results. It turns out that the great majority of the studies published so far on shape control are theoretical and numerical. Experimental testing to validate model predictions is very scarce. Although piezoceramic actuators have been the most widely considered for shape control, they present certain disadvantages that make them difficult to use in realistic industrial applications. For example, they exhibit a very brittle behaviour and are therefore vulnerable to damage. Moreover, it is difficult to make them conform to curved surfaces. To overcome the difficulties associated with using piezoceramic materials, piezoceramic composite actuators have been developed. Presently, there are three types of piezoceramic composite available commercially: 1-3 composites manufactured by Smart Materials Corporation, Active Fibre ACTIVE SHAPE CONTROL OF COMPOSITE STRUCTURES UNDER THERMAL LOADING Philippe Binette, Marie-Laure Dano, Guy Gendron Department of Mechanical Engineering, Laval University Keywords: thermal distortion, active shape control, piezocomposite, finite-element, experiment