Effect of thermal loading on metal/fiber-reinforced composite interface.

摘要

The increasing need for stronger and lighter structures in different industries has created a great interest in using Fiber-Reinforced Plastics (FRP) for primary structural purposes. In addition to fully-composite structures, there are also various cases where FRP is used as reinforcement to structures made from other materials, especially metals. As a result, the performance of the joint between FRP and metals in such hybrid structures is of significant design concern.;One of the objectives of this study was to establish the optimal lamination sequence that would result in the minimum thermal mismatch in the adhesive interface between composite and aluminum adherends. For this purpose, finite element analysis (FEA) was performed to examine the behavior of the adhesively bonded interface between aluminum and different composites subjected to thermal loading. Various types of FRP composite studied here included unidirectional, angle-ply, cross-ply and quasi-isotropic Glass/Epoxy and Carbon/Epoxy composites. Three-dimensional (3-D) FE models of the interface between aluminum and the various composites subjected to a thermal loading (from +25°C to -40°C) were constructed. Thermally induced stresses in the interface bond were calculated and compared for the different FE models. Based on results of this parametric study, the optimal lamination sequence for Glass/Epoxy and Carbon/Epoxy composites was established.;In the experimental phase of this research, adhesively bonded specimens composed of aluminum and four different composites (unidirectional and cross-ply GFRP and CFRP) were fabricated. These specimens were placed in an environmental chamber where they would be subjected to several thermal cycles (variations from +35 to -40°C). Specimens were tested after having experienced various cycles, and the performance of the cycled specimens was compared to the intact ones by using a three-point bending test. Finally the reduction in the performance of the joint due to thermal cycling was established.;It was concluded that the optimal lamination sequence in the composites adherends used in this study, for minimizing the thermal stresses in the bond between the composites and aluminum would be unidirectional 0°. Also it was shown that thermal cycling had significant adverse effect on the performance of the cross-ply carbon specimens, but it had negligible effects on the unidirectional 0° carbon specimens.;Adhesive bonding is one of the most commonly used methods of joining composite components together or to other materials. There are cases where such adhesively bonded structures would undergo severe changes in temperature. In any such case there is concern regarding the stresses arising due to thermal mismatch of materials. If such changes in the temperature occur repeatedly, it would be classified as cyclic thermal stress, which can have a more adverse effect on the structure than a gradual temperature change due to thermal fatigue.