Flowability of unidirectionally arrayed chopped strands in compression molding

This paper investigates the flowability of unidirectionally arrayed chopped strands (UACS) in compression molding of flat plates and rib structures. UACS is made by introducing regular slits into a unidirectional prepreg of carbon fiber. The stack of UACS plies is then cured into a laminate. To visualize the movement of the chopped strands, a UACS ply consisting of carbon fiber is inserted between glass-fiber plies. After molding, the glass-fiber layers become translucent, and the carbon-fiber chopped strands look black. This result reveals that the chopped strands are not only stretched in the transverse-fiber direction but are also moved in the fiber direction, following the extension of other layers. Furthermore, the interlayers slip easily, preventing direct contact between chopped strands during the formation of complex shapes. This demonstrates the excellent flowability of the UACS laminate even in high-volume-fraction fiber such as 60% where sheet molding compound (SMC) cannot flow smoothly.