The effect of prepreg edges in CFRP pipes on cure-induced internal states: distributed fiber-optic-based evaluation

Abstract

Residual stress and strain occur in CFRP pipes during the manufacturing process, which leads to defects in worst-case scenarios. Therefore, monitoring the state of composites and setting up an appropriate manufacturing process are essential. With the sheet winding method, prepregs are wound around a mandrel with each prepreg having an edge formed at the seam. Two forms of prepreg edges can exist: one where the prepreg edge has a gap, and the other, where the prepreg edge overlaps. This research examined the effects of the forms of the prepreg edges on the cure-induced internal states using a fiber-optic-based method. In the case of the edge involving a gap, strain level peaks at the prepreg edges were observed throughout the curing process. Meanwhile, the sample containing an overlap presented no strain level peaks during cooling. According to the results, it would be preferable to have overlapping present at the prepreg edges.