Papers by Keyword: Interlaminar Stresses

Abstract: A generalized higher-order global-local theory was presented. The transverse shear stresses can be got directly through the constitutive equation without using the equilibrium equation. The second derivative of interpolation function was deduced. The hammer integration of triangular area coordinate method was applied to solve the multiple integration problem of the element stiffness matrix. The order choice of numerical integration was discussed and results obtained through two different integration orders were compared. The flow of how to compile a FORTRAN program was given. A moderately thick composite laminated plate was analyzed via finite element method (FEM) based on the theory and results were compared with that of Paganos three-dimensional elasticity. It shows that the interlaminar stresses are accurate for moderately thick laminated plates.

Abstract: A novel stitching reinforcement method is applied to the laminates with cut-out for a decrease in the interlaminar stresses . The stitching parameters, such as the distance between edge and stitch line, the thread radius, and the stitch step etc.,are designed,and the three-dimentional models are established for FEM (Finite Element Method). The maximum circumferential shear stress appears in laminates of 0/-45, showing stress distribution similar to analytic solutions . The interlaminar circumferential shear stress of stitched is significantly decreased, and the validity of this method is proved.

Abstract: Traditional laminate strength analysis only considers face failure under in-plane loads. In fact, owing to the mismatch of the mechanical properties of the adjacent layers, a three-dimensional interlaminar singular stress fields develop in a small boundary region in the vicinity of the free edges of the laminate under mechanical load, which may lead to interlaminar delamination failure. Neglecting this interlaminar failure mode, the failure strength of laminate will be overestimated. In this paper, face failure and interlaminar failure are both considered. So for a lamina, three major failure modes are considered: matrix failure, fiber breakage and delamination. Finite element method is used to obtain the stresses in a laminate under mechanical loads. Stress-based criterions are adopted to predict the failure mode of laminas. When a lamina is failed, the lamina stiffness is reduced according to the corresponding failure mode, and the stresses of the laminate are re-analyzed. This procedure is repeatedly performed until the whole laminate fails and thus the ultimate strength is determined. The predicted ultimate strengths are in good agreement with experiment results in the open literature.