Performance of graphite/bismaleimide laminates with embedded optical fibers. I. Uniaxial tension

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Abstract
Optical fibers should not compromise structural integrity when embedded in smart composite structures for strain sensing. In particular, the tensile mechanical properties are of interest due to their use as basic design data for most applications. This study quantified the effects of the orientation and location of embedded optical fibers on the uniaxial tensile performance of graphite/bismaleimide (Gr/BMI) laminates. To investigate these relations, experimental strength and stiffness data were obtained and compared for eight different test configurations, each comprising five to eleven specimens fabricated with acrylate-coated 250 mu m diameter optical fibers embedded symmetrically or asymmetrically with respect to the laminate midplane, and parallel or perpendicular to the applied uniaxial loading and/or adjacent reinforcing fiber directions. All specimens were manufactured from G40-600/5245C Gr/BMI prepreg with a (03/902/0)s stacking sequence. Optical fibers were found to only modestly reduce the tensile properties of composite laminates (up to 10%) when embedded parallel or perpendicular to the applied uniaxial loading and/or adjacent reinforcing fiber directions. The largest reductions occurred in composite laminates with optical fibers embedded perpendicular to the loading direction and the adjacent graphite fibers. Thus, in order to decrease the extent of structural degradation, optical fibers should be embedded parallel to both the loading direction and adjacent reinforcing fibers.