Objective:
Asses the effect of embedded fiber optic sensor (FOS) on failure of unidirectional carbon/epoxy laminates.
Approach and Results:
Fabricated composite panels with mid-plane embedded FOS at various angles. Embedment found to cause an eye shaped defect (fig. a) and local geometrical distortion of reinforcing fibers. Conducted tension and compression tests and recorded failure modes and loads (see fig b). Results were compared with no FOS data. Modeled the idealized problem (fig a) by finite elements and calulated critical stresses (see figs c and d).
Results:
Failure initiation was by transverse cracking @A for tensil load and interfacial cracking @B for compression loading. Ultimate failure was by fiber fracture and kinking for tension and compression loads respectively. Em,bedding fiber optics at 90° to reinforcing fibers causes strength loss of up to 10% for tension and up to 40% for compression loading.
