Investigation Of Transient Thermal Transfer Of 3D Braided Composites

3D braided composites possess high specific strength, high stiffness, resistance impact, resistance fatigue and other excellent mechanical properties. At the same time, it also has the special performance of interlaminar crack and resistant layered due to the design of structure, the overall atypia characteristics. So they are widely used in the aviation, aerospace, military, medical, machinery, and many other fields. In recent years, many scholars research for a lot of mechanical properties of 3D braided composites, and made great achievements. However, due to the application scopes of 3D braided composites is more and more wide, it appear especially high temperature environment and alternating environment in aerospace applications. The thermal stress which the structure complexity of 3D braided composites generated can seriously affect the service life of the material. At present, it is not enough to research on the thermal performance of 3D braided composites. Many scholars only carry out the researches on thermal physical properties and the related parameters of 3D braided composite material. 3D four-directional braided composites is regarded as the research object, based on the heat transfer theory foundation, and the finite element method, Studied the transient heat conduction problem of 3D braided composites. at the same time, the transient temperature field distributies of the different boundary conditions is calculated, and the transient thermal stress calculation of the 3D braided composite material on the basis of temperature field is realized in this dissertation.First of all, three aspects from the geometric model of 3D braided composites, the basic mechanical properties research and the thermal study are summarized. In addition, the background, purpose and significance of the present project are elaborated too. And then mainly introduces the basic concept and the basic law of heat conduction theory and equilibrium equations of heat transfer theory in detail. At the same time, it introduced summarily a few kinds boundary conditions of encountering in the process of heat transfer. the theoretical basis of transient heat conduction and finite element equations is combined and provided the theoretical foundation on the transient heat conduction of 3D braided composites in this dissertation.Afterwards, the transient heat conduction equations of 3D braided composites is solved by using the precise integration algorithm. It verified on the accuracy of the transient heat transfer calculation of the three-dimensional braided composites by choosing the typical numerical example It also realized the transient heat conduction calculation of the different boundary conditions by Fortran programming software,and sumed up the temperature field of in the different boundary conditions distribution at any moment.Finally, the 3D braided composites transient thermal stress theory is deduced basing on the thermal stress of thermal elastic mechanics theory. In addition, it realized the calculation of the transient thermal stress on base of having calculated the temperature field by the transient heat conduction of 3D braided composites. It is summarized the influence of the braiding angle and the fiber volume content on the transient thermal stress of 3D braided composites in this dissertation.