Prediction of resin pocket geometry for stress analysis of optical fibers embedded in laminated composites

A linear elastic study is performed, as a first-order approximation, to investigate the geometry of the resin-rich region observed around fiber-optic sensors embedded in laminated 'adaptive' composites. The Rayleigh-Ritz method is employed with beam-bending functions as assumed trial functions. The total potential energy is minimized with respect to unknown force distributions in each layer and the unknown length of the resin pocket. The resulting system of coupled nonlinear equations is solved by the Levenberg-Marquardt algorithm to compute the shape and size of the resin pocket. Results of this analysis show the effect of laminate stacking sequence, lamination pressure, and optical fiber diameter on the geometry of the resin pocket; and are found to agree well with experimental observations. The computed geometry is automatically discretized for finite-element analysis in order to obtain stress information in the vicinity of the resin pocket.