IN-SITU MEASUREMENT OF CFRP PREPREG DEFORMATION IN COMPLEX SHAPED PART USING EMBEDDED OPTICAL FIBER BENDING SENSOR

摘要

Process-induced shape distortion of complex shaped composite parts leads to high manufacturing cost and low productivity. Especially, thickness variation resulting from resin flow, prepreg compaction and cure shrinkage leads to time-consuming assembly using shim, but its mechanism is not fully understood yet because there was no in-situ measurement technique that can clarify internal kinetics of prepreg before gelation. This study developed an innovative bending sensor, which is a small-diameter optical fiber sensor (diameter 52 micron) embedded in both sides of a thin cured CFRP laminate (thickness 125 micron), to measure through-thickness deformation of prepreg that leads to thickness variation. The bending sensor was embedded in a corner section of an L-shaped CFRP laminate to measure real-time strain distribution change during curing process. The bending sensor sensitively detected through-thickness deformation during vacuuming and heating, and the sensor response indicated corner thinning and flange thickening.