In-situ Consolidation Deformation of Composite Laminate with Gaps of Various Widths

Gaps between prepreg tapes, which occur when prepreg tapes are placed automatically, cause concave deformation of the laminate during consolidation, which degrades the quality of the cured laminate. However, this in-situ concave deformation has never been measured. This study measures consolidation deformation of a cross-ply thermosetting composite laminate containing gaps of various widths at the middle layer. A unique fiber-optic-based shape sensor is used for the in-situ deformation monitoring and the deformation during autoclave pressurization and heating is presented. The results indicate that the deformation phenomenon depends on whether the upper bagging-side layer bridging the gap contacts the tool-side layer below the gap as it sinks into the gap during consolidation. The consolidation process reveals when the gap width is narrow, the fibers and the resin from the prepreg layer flow into the gap and displace upwards the sunken upper layer, partially reducing the concave deformation. One attempt to suppress gap-induced deformation is also made by using a curing condition inspired by the observation and understanding of this deformation mechanism.