A Study On The Stress And Damage Of Fiber Winding Composite

The filament-wound case (FWC) plays a more and more important role in the solid rocket motor chamber structure (SRMCS) with composite material widely used in spaceflight fields. The work of this thesis is under the engineering background of project -Study on distortion and damage of filament-wound SRMCS. Case A we called here is a type of SRMCS based on designing method A. Case B was redesigned based on Case A in order to meet the needs of enhancive warhead mass, but it burst under low pressure. In order to find out the reason of bursting under low pressure, macro stress and strain of SRMCS were analyzed by using compound theory, netting theory and nonlinear finite element method (FEM). It was concluded that the damages of the SRMCS led to the bursting of Case B under low pressure. Then it was necessary to study the matrix crack and delamination damages in detail, which occurred with the maximum probability and played the most important role on FWC failure. Two models about damage analysis were established by using energy method and shear lag method. The mechanism of damage and the effect to structure performance caused by damage are studied further.First, three kinds of analytical methods including netting theory, compound theory and nonlinear FEM were performed to obtain the stresses and deformations of SRMCS. Based upon the facts that parameters were unequal in thickness and winding angle along the meridional direction, some fitting formulations were proposed in the FEM model. This FEM model could also represent geometrical nonlinear behavior by considering large displacements. A kind of quadrilateral composite element was firstly used in large structures such as SRMCS, in which at least five layers can be contained in one element along thickness direction, thusthe calculation results will be more precise although divided the structure into less elements. By way of comparing the results obtained from netting theory, compound theory, nonlinear FEM and experimental test, the conclusion could be drawn that matrix crack damage surely existed in the cylinder part of structure. When the structure was subject to internal pressure up to 6.8MPa, which was the maximum loading of hydrostatic test, the deformation of the global structure and stress and strain distributed in any parts of structure were obtained. A fairly good agreement was obtained between the analysis and the test results. And it was proved that it is reasonable to analyze the FWC using nonlinear FEM. The results of case A and case B were about the same, thus it was displayed that modifying structure did not cause the bursting under low pressure but the damages of the structure.Second, an analytical model was developed to assess the critical buckling problem of near surface interlaminar rectangular defects in the cylindrical part of SRMCS under axis and interior pressure loads. The relationships between critical strain value and the parameters of geometry and radius of cylindrical were discussed. With the different loading ratio of parallel to axis and normal to axis direction, damage defects will occur bulking problem. By varying the degree of material anisotropy relative to the loading axis such as Poisson's ratio and shear modulus, crack growth bulking strain value parallel to or normal to the loading axis is different. The parameters controlling the growth or arrest of the delamination damage are identified as the geometry and the depth of defects and radius of cylindrical etc.At last, it was investigated that the delamination damage is often induced by the tip of matrix damage under higher stress. A complete parabolic shear-lag analysis containing delamination damage induced by transverse cracks wasproposed and applied to predict the global properties of materials. The predictions from the complete parabolic shear-lag analysis without containing the delamination, incomplete parabolic shear-lag model and the complete parabolic shear-lag analysis proposed in this paper have been compared. The results show the complete parabolic sh...