On the Use of Planar Shear-Lag Methods for Stress-Transfer Analysis of Multilayered Composites

Shear-lag equations for analysis of stresses in a multilayered composite were derived using a series of approximations to exact two-dimensional elasticity methods. The shear-lag equations derived with the fewest assumptions was termed the Optimal, Shear-Lag Analysis for planar problems in composites. A solution method for these equations was outlined based on eigen-analysis of a matrix of shear-lag parameters. The optimal, shear-lag analysis differs from most prior shear-lag methods in the literature. By adding more assumptions, we could reduce the optimal analysis to two common, prior shear-lag methods. These prior methods were labeled as Interlayer, Shear-Lag Analysis and Parametric, Interlayer, Shear-Lag Analysis. Because theses two interlayer methods required more assumptions than the optimal method, they are less accurate than that method. Several examples illustrated the types of problems that can be accurately solved by shear-lag analysis and the differences in accuracy between the various shear lag methods. The results of this paper can be used to guide the derivation of future, improved shear-lag models or to evaluate the quality of prior shear-lag models.