The performance of graphite-epoxy composite with embedded optical fibers under compression

The effect of embedded optical fibers on the compressive strength and stiffness of a graphite-epoxy composite, AS4/3501-6, consisting of 30 plies with 40% 0 degrees plies, 20% 90 degrees plies, and 40% +/-45 degrees plies, was investigated. Five laminates were fabricated with different numbers of optical fibers, optical fiber diameters, optical fiber locations, and optical fiber orientations with respect to reinforcing graphite fibers, which provided 15 groups of specimens. Each group contained 10 specimens which were tested under compression using an IITRI fixture. Optical fibers were oriented perpendicular to the loading direction in all specimens. The maximum reduction in compressive strength was 27% in specimens where two optical fibers were placed perpendicular to surrounding graphite fibers. In this case, one optical fiber was located at the specimen midplane while the other was located three plies from the outer surface, resulting in an asymmetric condition about the midplane. Other variations of optical fibers perpendicular to graphite fibers resulted in less reduction and in some cases did not affect the compressive strength. All specimens where the optical fibers were placed parallel to reinforcing fibers resulted in no degradation of the compressive strength. No change in modulus was observed due to the presence of optical fibers in any group of specimens.