Generalized Shear-Lag Analysis Including Imperfect Interfaces

Two recent papers showed that shear-lag analysis can be an effective tool for stress analysis of composites when done properly and when applied to problems for which it is appropriate. This paper extends the prior analysis of concentric cylinders to a generalized shear-lag analysis in which the transverse variations of shear stress are described by arbitrary shape functions. The shear-lag analysis and solution can be derived in terms of averages of the new shape functions. The shape functions can be specified after analysis and tailored to suit specific problems. This paper also extends shear-lag analysis of both concentric cylinders and multilayered structures to model imperfect interfaces between the layers. The generalized methods were applied to several issues in fiber/matrix stress transfer modeled as two concentric cylinders. By modifying prior shape functions, it was possible to extend shear-lag analysis to work for any fiber volume fraction. Prior shear-lag models were all unacceptable at low fiber volume fraction. The full shear-lag analysis can model stress transfer for both isotropic and anisotropic fibers. The new imperfect interface capability was used to interpret experimental results for fiber/matrix stress transfer in terms of interface quality.