Mechanical performance of composite flat specimens and pressure vessels produced by carbon/epoxy towpreg dry winding

Abstract

The main purpose of this study is to evaluate the effects of certain processing parameters on the mechanical performance of carbon/epoxy towpreg wound composite structures. For this purpose, composite sample productions and their evaluations were conducted in two steps. In the first step, dry winding of carbon/epoxy towpregs was used to produce flat composite plates. Their evaluation was performed by rheological analysis, interlaminar shear tests, and unidirectional tensile tests. In the second step, towpreg dry winding was used to produce composite pressure vessel samples. Their performance was evaluated by observing the effects of various winding process parameters on the safety of the vessels via hydrostatic burst pressure tests. Compared to the traditional wet filament winding, the main difficulty observed was maintaining the “straight towpreg path” necessary for efficient winding operations. This problem was prevented by applying higher tension forces during dry winding. Evaluation of the hydrostatic burst tests in terms of burst pressure, hoop strain and safe failure mode revealed that the optimum pressure vessel performance could be obtained in the vessel samples with “helical-hoop-helical winding layer sequence.” On the other hand, use of “complex helical pattern” resulted in no advantages at all, due to basically higher number of undulation zones acting as stress concentration zones.