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This study investigates the use of macro-fiber composite (MFC) actuators to compensate thermal deformation in composite structures. The specific objective is to determine if MFC actuators bonded on the surface of a composite plate have the ability when actuated to counteract thermally induced deformations. Both finite-element analyses and experiments are presented. First, the response of an aluminum plate and a unidirectional composite plate both subjected to a MFC actuator is predicted. Next, the response of an unsymmetric composite plate with two MFC actuators bonded on the surface is studied. In the first step, a uniform temperature change is applied which induces a large change in the structure shape due to the laminate's unsymmetric nature. In the second step, the MFCs are actuated to compensate the thermally induced distortion. The results show that MFC actuators can eliminate thermal deformations when a proper amount of voltage is applied. Finally, a series of experiments are conducted to study the piezoelectric effects and provide data to compare with the finite-element results. Correlation between experiments and simulations is excellent.

The use of bistable unsymmetric cross-ply laminates for morphing application has received growing attention in the last few years. So far, most studies use large rectangular piezoelectric Macro Fiber Composite (MFC) patches bonded at the center of the laminate to induce snap-through. However, the use of large rectangular MFC patches bonded in the center of the laminates significantly influences the shape of the laminate by greatly reducing the curvature at the midsection of the laminate where the MFC patches are bonded. This paper presents a study where narrow cocured MFC strips distributed over the entire surface are used to induce snap-through of unsymmetric cross-ply laminates. This MFC configuration allows having a more uniform curvature in the laminate. Since the strips are bonded on both sides, reverse snap-through should be obtained. The study was both theoretical and experimental. A finite element nonlinear analysis was used to predict the two stable cylindrical configurations and the snap-through induced by MFC actuation. For the experimental study, a laminate-MFC structure was manufactured and tested. The shapes were measured using a 3D image correlation system as a function of applied voltage. Good correlations for the cylindrical shape and displacement field were observed.

a b s t r a c tThis study investigates the performance of three-dimensional (3-D) woven interlock composite plates subjected to impact loading. Low velocity (lower than 10 mÁs À1 ) impacts with highly deformable rubber impactor are addressed. Response variability is investigated by conducting several impact tests in the same conditions. The effect of mass and velocity on damage tolerance is studied by varying the impact conditions. Force-time, displacement-time and force-displacement curves are first analyzed in such various impact conditions. Secondly, damage mechanisms are highlighted through microscopic observations. The large geometrical deformation of the rubber impactor during impact leads to a loading less localized than for a hard impactor which induces a wide spread damage distribution. Comments on the relations between damage states and mass-velocity conditions are proposed.Crown