Experimental Studies Of Viscoelastic Composite Materials' Nonlinear Dynamic Characteristics

Experiment can proof-test that whether the theories are correct for the existed phenomenon or not. Besides, when we come across some unknown ones that are unable to be explained by these existed theories, experiments can be the pioneer who will explore these new phenomenons first and give some help to the theorists for their improvement work in theories. Especially in the forward topics of complicated dynamical behavior of nonlinear oscillatory systems, we are confronting more and more new fresh research objects, such as polymeric material, fiber composites, biomaterial, geology material and so on. They are applied popularly in the field of aerospace engineering, civil engineering, underground engineering, oceanographic engineering, bioengineering and material engineering. Resin-based nanocomposite is one kind of viscoelastic materials. As it have intensive effects in time, temperature and frequency, it's difficult to analyze it with theory or calculating. Therefore, finding the suitable experiment research method and combining the results with theory have great significance and application value. This thesis is devoted to explore the nonlinear dynamics system consist of viscoelastic structure with unknown parameters, by mechanical model experiments.Dry friction is one of typical nonlinear dynamic phenomenon which is mainly famous for the hysteretic nonlinear characteristic. On the basis of the Metallic Material's Dry Friction research by the former researchers, we utilized the same equipment to test several viscoelastic materials' dry friction characteristic. Analyzing the experimental data we get some useful results on several aspects such as hysteretic curve, equivalent damping and surface tangential stiffness. Through comparing the viscoelastic material and metallic material's difference, we find the suitability and limitation of the temporary dry friction theories for these two kind materials.Parameter oscillatory is of most important research value in the nonlinear dynamic. Lots of theory and experimental researches on this system which is mainly composed of elasticity material have showed richness valuable nonlinear results. In this thesis, we try to do some research on the viscoelastic material, combined with a controllable and measurable dry friction damping into a parameter-excited vibration system. This system is basically composed of an inflected beam which has one fixed side and one adjustable pressure slip side, which will receive harmonic excitation. Though our own mechanical model experiment platform's design and followed test, we get large number of data and analyze some nonlinear phenomenon, by changed different parameters and compared different materials. Besides, in order to identify the correct theory model of this viscoelastic experiment structure, sufficient practical data have been provided from the mechanical model experiments.