Abstract:

In order to study the relationship between the flow behavior and the structure of warp-knitted quadri-axial glass fiber fabric, the planar permeability and the unidirectional permeability of the preforms with different ply numbers and ply angles were measured by radical flow permeability test method and unidirectional permeability test method. The cross-section of the composite was analyzed to identify the impediment effect on flowing by fabric’s concave and convex surface. The unidirectional permeability of multi-layer preforms was predicted by empirical formula with the variation of fiber volume fraction. The experimental results show that  no direct relationship exists between the permeability and the fiber volume fraction in preform with lower ply numbers. However, the permeability is closely related to the number of flow channels which are formed by the fabric surface under compression and parallel to the flow direction. For preforms with different ply angles, the one with the largest number of parallel flow channels has the highest permeability. The empirical formula was more accurate comparing with the Kozeny-Carman formula in predicting the unidirectional permeability of the warp-knitted quadri-axial glass fiber fabric.

Key words: liquid composite molding, fiber reinforced composite, permeability, warp-knitted quadri-axial fabric, glass fiber fabric