Effect of gaps on preform and laminate made by automated dry fiber placement and resin infusion

Abstract

Automated Dry Fiber Placement (ADFP) provides ease in fiber steering compared to the automated placement of prepregs and a higher material deposition rate than manual hand layup. Vacuum Assisted Resin Infusion (VARI) can be used to infuse the resin into the bed of dry fibers to make the composite. The resin flow rate depends on the permeability of the dry fiber preform, which is dependent on the preform fiber volume fraction. Automated Fiber Placement (AFP) allows the capacity to control the fiber volume fraction in terms of gaps between the tows. So, reducing the fiber volume fraction of preforms by introducing gaps into the preform pattern can increase the permeability. On the other hand, introducing gaps in layup results in a drop in the mechanical properties of the laminate (such as compressive modulus and strength). An optimum gap size may provide a significant gain in permeability with minimum loss in compressive properties. This paper investigates the effect of the gap size in the preform pattern on the preform out-of-plane permeability and compressive properties of the laminate. The out-of-plane permeability of three specimens from preforms, with varying gap sizes (0mm, 0.4mm, and 0.8mm) in all layers were measured. Also, the compressive properties of five coupons made from laminates, with and without gap sizes (0mm, 0.4mm, and 0.8mm) were determined. It was shown that introducing gaps with 0.4 mm size between fiber tapes in the layup can increase the out-of-plane permeability 17 times and reduce the compressive strength and modulus by 6 % and 7.2 %, respectively.