Ability to determine the individual stresses photoelastically in orthotropic composites from isochromatic data, but without employing isoclinics or isopachics, is developed and demonstrated. This new capability is achieved by combining isochromatic information, complex stress functions and numerical nonlinear least-squares concepts into a new and effective hybrid method for stress analyzing composite materials. Unlike previous methods of photo-orthotropic-elasticity, the present technique simultaneously smoothes the recorded isochromatic data, provides reliable boundary information, and separates the isochromatics into individual stress components throughout the area of interest. The method is illustrated by evaluating the three individual stresses throughout a region adjacent to a hole in a uniaxially loaded orthotropic composite plate from the measured isochromatics.

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This article presents a new non-uniform finite strip technique for analyzing composite laminates having both material and geometrically non-uniform cross sections. This is an extension of the conventional concept of the finite strip method which deals with uniform cross sections only. The application of the proposed method for flexed composite plates is illustrated. Numerical results are demonstrated for a transversely loaded circular composite plate containing an eccentric hole and are compared with those from an independent finite element analysis and with measured data. The spectral convergence characteristics of the non-uniform strips are discussed, and the enhanced accuracy and reduced computer efforts are compared with those for the conventional finite element method.