Study On Damping Of Fibre Reinforced Resin Composites And Structures

Under outside interference or dynamic loads, mechanical systems and power equipments will produce vibration and noise, which are harmful on the systems themselves and environment. It is necessary to have a sound methodology to control vibration and lower noise. Using high damping materials or damping structures is one of the very effective ways to solve these problems. Fibre reinforced epoxy resin composite materials have a higher damping property than metals by 1~2 orders of magnitude. And they can be directly used as vibration components because of their excellent mechanical properties. Therefore it has become a hot spot in the research field of damping materials. The purpose of the paper is to improve structure damping performance of materials by damping structure optimization design, based on the study of damping of resin composites.Firstly, the paper presents an analysis of the damping properties of unidirectional and three-dimensional (3-D) braided carbon fibre reinforced epoxy resin composite materials, including natural frequencies, damping loss factors and mode shapes. Damping modeling is implemented using a finite element method based on mode analysis theory and strain energy method. The experimental damping properties are obtained using vibration mode test system. The simulation results obtained show that the modeling describes the experimental results fairly well. Next, the results of the above study are applied to the analysis of the damping structure optimization of a rectangular plate, which builds a good foundation for the analysis and engineering application of the damping of composites and structures.For the damping research of unidirectional composites, The simulation results of natural frequencies for the first four bending modes are obtained for specimens with the fiber orientation angle of 0°, 45°, 90°, respectively, and compared with the experimental results. The simulation results are in good agreement with experimental results, which indicates the rationality of the model. Next, the influence of fibre orientation on the damping properties of the composites is studied. It shows that the influence of fibre orientation on the damping loss factors is different with the fibre orientation and natural frequencies decrease when the fibre orientation angle is increased.For the damping research of 3-D and 4-step braided composites, a method combining macrostructure and periodic microstructures is developed for damping modeling of the composites. The simulation results of natural frequencies for the first four bending modes are obtained for specimens with the braiding angle of 30°, 40°respectively, and compared with the experimental results, which indicates the rationality of the model. And the influence of braiding angle on the damping properties of the composites is discussed. It shows that damping loss factors increase and natural frequencies decrease when braiding angle is increased.Based on the above study, the damping structure optimization design of a rectangular plate is analysed considering stacking sequences, material structure and hybrid composites. Laminates with three different stacking sequences were analysed: [0/90/0/90]s cross-ply laminates, [0/90/45/-45]s laminates and [θ/-θ/θ/-θ]s angle-ply laminates. The damping of braided structure and laminate structures are compared. The damping of braided structure is higher than parts of laminate structures. For carbon/glass fiber hybrid composites, the damping loss factor of the hybrid composites is between glass fiber composites and carbon fiber composites. The damping loss factor of the hybrid composites is increased when glass fiber content is increased and decreased when carbon fiber content is increased. The research of material damping and structure damping is combined in the study, which provided theoretical guidance for the design and study of new damping materials and structures.