Permeabil ity of stitched preform in RTM

The permeability of stitched preform was measured by the radial technology. The influences of the sewing needle and stitching parameters on the permeability were studied. The experimental results show that the permeability increases with increasing the stitching density and diameter of sewing needle except when the stitching density is  lower than 0. 66 pts/m using 100 type sewing needle. The types of the sewing needle and thread affect the permeability simultaneously. The sewing needle plays a promoting role , while the thread plays a limiting role. With a thread mass fraction of 0. 18 % , the permeability is increased greatly by 58. 6 % with respect to the same unstitched fabric. Transverse permeabilities of stitched and unstitched fabrics were measured by one-dimensional flow experiments. The influences of the fiber stacking sequence and stitching density on the transverse permeability were studied. The experimental results show that the transverse permeability strongly increases with increasing the stitching density.