Experimental characterisation of large in-plane shear behaviour of unidirectional carbon fibre/epoxy prepreg tapes for continuous tow shearing (CTS) process

The continuous tow shearing (CTS) process is an advanced tape placement technique with the ability to steer unidirectional prepreg tapes by in-plane shear deformation without the presence of tape buckling, gaps and overlaps. However, the inherent fibre misalignment within the tape can induce fibre waviness during the shearing process, which is further affected by processing parameters such as temperature, shear rate and fibre tension. In this paper, the effect of those parameters on the shear behaviour of two different unidirectional carbon/epoxy prepreg tapes was experimentally investigated. A bespoke test fixture was designed to shear the tape specimens at various shear rates and fibre tensions. Digital image correlation (DIC) was used to obtain full-field strains of the specimens to investigate the fibre realignment during shearing. Experimental results showed that both temperature and fibre tension significantly affect the uniformity of the fibre realignment. Moreover, the responses of the two prepreg tapes under the same shearing condition were different due to their different impregnation characteristics.