Meso-mechanical Analysis On Dynamic Viscoelasticity Of Fiber-reinforced Composites

Dynamic viscoelasticity of fiber reinforced composites were studied experimentally,theoretically and numerically in this thesis.Firstly, the static and dynamic experiments for resin material, unidirectional composite,laminated layer and3D woven composite were carried out. From the experiments mentioned above,the static and dynamic parameters of all these materials were obtained. Another experiment ondynamic properties of composites exposed to wet and hot conditions was also worked out, andcompared with dry condition, the attenuation of these composites became more and more noticeable.An isotropic viscoelastic constitution was built to describe the time dependent properties of resinmatrix phase in composites. The viscous wave theory was developed to describe the stess attenuationof resin material, and the parameters in the model were determined from creep experiment of pureepoxy and viscous wave theory. Then, based on the deformation compatibility conditions, transverseisotropic model for unidirectional composite and orthogonal viscoelastic model for laminated layerand3D woven composites were developed, respectively. In a further way, the dynamic relaxationmodulus of these materials were studied with micro models. A method for analyzing the dynamicparameters of vicoelastic material was brought forward, and the predicted damping ratio, dynamicstorage modulus, loss modulus and loss factor are all in good agreement with experimental results.Finally, micro and macro FEM models of unidirectional composite, laminated layer and3Dwoven composite were built. The relaxation modulus of composites calculated by theoretical modelsand the results of natural frequency obtained in the experiment were verified by micro and macroFEM models, respectively. Therefore, FEM models fully proved the theoretical method andexperimental results in this thesis were accurate.This research is supported by the National Natural Science Foundation of China through GrantNo.10772078and10472045.This research is supported by State Key Laboratory of Mechanics and Control of MechanicalStructures...