Development and characterization of orthotropic-birefringent materials

Abstract

Materials were selected and fabrication procedures developed for orthotropic-birefringent materials. An epoxy resin (Maraset 658/558 system) was selected as the matrix material. Fibers obtained from Style 3733 glass cloth and Type 1062 glass roving were used as reinforcement. Two different fabrication procedures were used. In the first one, layers of unidirectional fibers removed from the glass cloth were stacked, impregnated with resin, bagged and cured in an autoclave at elevated temperature. In the second procedure, the glass roving was dry-wound over metal frames, impregnated with resin and cured at room temperature under vacuum and pressure in the autoclave. Unidirectional, angleply, and quasi-isotropic laminates of two thicknesses were fabricated. The matrix and the unidirectional glass/epoxy material were fully characterized. The density, fiber-volume ratio, mechanical, and optical properties were determined. The fiber-volume ratio was over 0.50. Birefringent properties were in good agreement with predictions, based on a stress-proportioning concept and also, with one exception, with properties predicted by a finite-element analysis.