Some New Results on Edge Effect in Symmetric Composite Laminates

Abstract

An improved numerical (finite element) procedure is developed to investigate the stress field in symmetrically laminated composites of finite dimensions. Emphasis is placed on assessing the singular behavior of stresses in regions close to ply-interfaces and the exposed free edge. An accurate evaluation of these stresses will help to better understand the failure process of composite laminates. Mechanical load in the form of uniaxial tension and environmental variables such as temperature and humidity exposures are considered in the formulation. Results tor lam inates under uniaxial tension are presented in this paper; thermal and hygroscopic stresses will be reported in a subsequent paper.

A variational model for free-edge interlaminar stress analysis in general symmetric and thin-ply composite laminates

“…In order to validate the developed methodology and the associated software implementation, the results predicted by the present model are compared with the well-known 3D finite element results of Wang and Crossman [20,21] αA=0.36×10 -6 0 C -1 , αT=28.8×10 -6 0 C -1 , 2W=16× tply…”

“…Moreover, it is shown how the strain and displacement fields can be determined when using a variational model based on the minimum complementary energy principle. The results obtained from the developed approach are compared to the available refined finite element results [7,20,21] for cross-ply, angle ply and quasi-isotropic laminates. The comparisons of stress and displacement fields under both mechanical and thermal loads show an excellent agreement.…”

Residual Thermal and Moisture Influences on the Strain Energy Release Rate Analysis of Edge Delamination

“…Therefore, the gradients of displacements, strains, and stresses, with respect to the x coordinate are zero [15][16][17][18], and only one x = constant plane must be analyzed. crack extension technique [19].…”

“…Hence, for an asymmetric sublaminate, equations (AIO) -(AI2) would be summed in equation (A9), instead of using equation (AIO) alone, to calculate strain energy density, uSUB' and is used in the strain energy release rate calculation of equation (17). Figure 14 Consider a laminate subjected to a temperature change of ~T and no other loading.…”

“…An experimental study indicated that for T300/5208 graphite-epoxy composites, the inclusion of residual thermal and moisture stresses , did not significantly alter the calculation of inter1aminar fracture toughness from ' strain energy release rate analysis of edge delamination data taken at room temperature, ambient conditions. 17 …”