Delamination detection in laminate composites with an embedded fiber optical interferometric sensor

The detection of delamination is an important aspect in the non-destructive evaluation of composite laminates. The paper presents a delamination detection technique based on fiber optic interferometry. A quasi-impulse loading is applied and the total elongation of an optical fiber embedded along the neutral plane of the laminate is measured as a function of load position. When a delamination is present, the shift of neutral axis position can be clearly reflected in the fiber integral strain versus load position plot. In this study, we have developed a fiber installation procedure that can ensure low probability of fiber breakage during autoclaving of the composite laminate. With laminates containing optical fibers, mechanical tests were performed. Experimental results clearly demonstrate the feasibility of detecting both the size and location of delamination with the proposed technique.