This paper is aimed at analyzing stresses and fiber-matrix interfacial debonding in three-dimensional composite microstructures. It incorporates a 3D cohesive zone interface model based element to simulate interfacial debonding in the commercial code ABAQUS. The validated element is used to examine the potential debonding response in the presence of fiber–fiber interactions. A two-fiber model with unidirectional fibers is constructed and the effect of relative fiber spacing and volume fraction on the stress distribution in the matrix is studied. In addition, the effect of fiber orientation and spacing on the nature of initiation and propagation of interfacial debonding is studied in a two-fiber model. These results are expected to be helpful in formulating future studies treating optimal fiber orientations and payoff in controlling fiber spacing and alignment.

Many composite problems are generalized plane strain in nature. They are often solved using three-dimensional finite element analyses. We propose a technique to solve these problems with a plane-strain model, which is achieved by introducing some artificial out-of-plane thermal strains in a two-dimensional finite element analysis. These artificial thermal strains are chosen such that an identical stress field is obtained, while the actual strains and displacements can also be determined.

In this work, we have employed a variational model to examine the effect of fiber-matrix debonding on the thermoelastic response of a unidirectional composite. The model is designed to represent the concentric cylinder model of a composite representative volume element and it contains the capability to enhance the accuracy of a given numerical solution. The effect of the extent of debonding as well as fiber volume fraction on all the effective moduli of the unidirectional composite has been examined. Numerical results reported in the literature are compared with the results of the model developed in the present study to examine the quality of the model.

The thermal stress analysis of thermally degrading tape wound phenolic composites in rocket nozzles is complicated by the extreme variation of properties with temperature, combined with steep temperature gradients on the order of 50,000° F/in. This study applied two very different numerical approaches to the same problem of predicting thermal stresses in a moderately thick conical frustum. One method uses a variational theorem derived by Reissner while the other applies the classical finite element method based on minimization of the total potential energy. The good agreement of the two methods appears to validate the results and an extensive convergence study is presented that identifies the magnitude of errors in the finite element method as a function of element density. A modification to the finite element method to account for intra-element material property variation is shown to improve the convergence of the procedure.

An approximate elasticity solution is developed for the response of the finite-width, angle-ply composite laminate under uniform axial strain. The solution yields components of the displacement vector, strain tensor, and stress tensor in the form of sinusoidal-hyperbolic series. Results of the approximate solution are compared to numerical solutions of the exact equations for four-layer, symmetric laminate geometries. The nature of the boundary disturbance in the eight-layer laminate is also examined by the approximate solution.

In this work, a general solution for the elastic stress field in a cylindrically anisotropic body, the hollow circular cylinder, under surface tractions which do not vary along the generator and which can be expressed in the form of a Fourier series, is presented. The form of the solution is sufficiently general to permit direct extension to an important class of composite structures, namely, laminated circular cylinders. Some of the peculiar effects of anisotropy are illustrated by the solution of a specific boundary-value problem—a circular hole in a large plate under tension.

A bending theory for anisotropic laminated plates developed by Yang, Norris, and Stavsky is investigated. The theory includes shear deformation and rotary inertia in the same manner as Mindlin’s theory for isotropic homogeneous plates. The governing equations reveal that unsymmetrically laminated plates display the same bending-extensional coupling phenomenon found in classical laminated plate theory based on the Kirchhoff assumptions. Solutions are presented for bending under transverse load and for flexural vibration frequencies of symmetric and nonsymmetric lamninates. Good agreement is observed in numerical results for plate bending as compared to exact solutions obtained from classical elasticity theory. For certain fiber-reinforced composite materials, radical departure from classical laminated plate theory is indicated.