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.

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Composite materials are sensible to temperature variations which can lead to the development of internal stresses. The induced stresses may be large enough to damage the material. The objective of this study is to evaluate the effects of extreme temperature cycles on three cyanate ester laminates and one sandwich panel. Thermal cycles going from −170℃ to 145℃ were conducted up to 360 cycles. Microscopic observations of the edges and the middle section of the specimens were performed to evaluate damage growth. Three types of damage were observed in the laminates: transverse microcracks, debonding between the fibers and the matrix and to a limited extent delamination. However, debonding between the fibers and the matrix were only visible on the edges of the laminates. The effect of the observed damages on the mechanical properties of the laminates was studied. Results show that properties influenced by matrix behavior were affected by thermal cycling.

The effect of extreme cold temperatures on the quasi-static indentation and the low velocity impact behavior of woven carbon/epoxy composite sandwich panels with Nomex honeycomb core was investigated. Impact tests were performed at room temperature, –70°C, and –150°C. Two sizes of hemispherical impactor were used combined to three different impactor masses. All the impact tests were performed at the same initial impact velocity. The effect of temperature on the impact behavior is investigated by studying the load history, load-displacement curves and transmitted energy as a function of time curves. Impact damage induced at various temperatures was studied using different non-destructive and destructive techniques. Globally, more damages are induced with impact temperature decreasing. The results also show that the effect of temperature on the impact behavior is function of the impactor size.