Numerical Study On The Mechanical Performance Of Fiber Stitched Lightweight Thermal Protection Structure

The severe aerothermodynamic environment of the hypersonic vehicle put forward a harsh requirement for the lightweight and excellent mechanical properties of the thermal protection structure.The research object of this paper is a fiber stitched lightweight thermal protection structure for hypersonic vehicles.In this paper,the mechanical behavior of the fiber stitched lightweight thermal protection structure is numerical simulated under the condition of the mechanical load,aerodynamic heat load,vibration load and noise load.The influence rule of the process parameters on the mechanical properties is obtained and the mechanical mechanism for this rule is explored through this work.The main contents are as follows:(1)A meso-finite element model is established for the lightweight thermal protection structure of the hypersonic vehicle.The interaction of the composite weaving panel,air-gel insulation core and stitched fiber is taken into account.What's more,this model consider the bonding effect between the thermal protection structure and the metal body.The model not only reflects the physical reality of the thermal protection structure,but also makes the reasonable simplification to make the computer can be solved.(2)The effect of structural parameters(thickness of panel,thickness of insulation core,density of stitched fiber and the degree of ceramicization for stitched fiber)on the mechanical properties is studied.Indicating that,with the increasing of the density or the diameter of the stitched fiber,the stress state under the typical working condition of the structure is improved.Simultaneously,with the structure thickness increasing,the stress level of the stitched fiber increasing which is harmful to the improvement for the the stress state of the structure.(3)Based on the numerical simulation method,the UMAT subroutine of the damage and failure analysis of stitched fiber bundles,composite weaving panels and air-gel core materials is programmed.The failure behavior of the thermal protection structure under the out-of-plain stretching and compression loads is studied.Meanwhile,the experiments under typical working condition of the mechanical properties for the structure are conducted.The results of the numerical simulation are matched well with the experiments data.All in all,the analysis of the stress and strain fields for the stitched lightweight thermal protection structure under the mechanical load,aerodynamic heat load,vibration load and noise load is put forward in this paper.Furthermore,the progressive damage and failure calculation method can use to engineering design and the strength check of the thermal protection structure.