Experimental determination of stress concentrations in orthotropic composites

Determining stress raisers necessitates accurate knowledge of the stresses on the edge of the geometric discontinuity. Recognizing difficulties in obtaining measured stresses at the edge of a hole or notch, the least-squares method, in conjunction with a Laurent series representation of the stress functions and local collocation, is used to evaluate reliable stresses on the boundary of holes in loaded composites from measured data away from the hole. Advantages over previous such hybrid analyses include the fact that few measured input data are required, that they can be arbitrarily located and that only a very few terms are needed in the stress function representation. The approach is illustrated for stress input as well as moire-measured displacements. Application to each of the three classes of orthotropy is deliberately addressed.