Study On Resin Impregnation And Flow Behavior For Fiber Preform Of Multi-walled Structure

Polymer matrix composite multi-walled structure refers to the structure with three or more connected or crossed walls. It attracts much attention because of its light weight, high load capacity, and resistance to deformation. Vacuum infusion molding process (VIMP) has become a hot research field of material manufacture because of its low cost, and it is also environmentally friendly and suitable for large composite structures. An effective control of the rein flow behavior during VIMP, and a fully impregnation are critical for ensuring the product quality.Based on the characteristics of multi-walled structure, effects of the corner, variable cross-section and variable permeability on the resin flow behavior are studied in the paper. The main results are as follows:1. During the VIMP, both the apparent permeability and the overall liquid filling speed of the resin impregnation reduced, regardless of the application of distribution medium, indicating the presence of the corner effect.When the distance between the corner location and the injection gate becomes larger, the apparent permeability of the fiber perform will decrease first, and then increase.When using the distribution medium, resin filling speed on a vertical flat surface is slower than that of a flat surface, and the gravity is the main factor affecting the speed differences. While the distribution medium was lied on top of the perform, its effect on speeding the resin impregnation is growing weaker as its distance to the injection gate grows. The corner effect can be weakened through applying distribution medium to the corners.2. For the fiber perform with variable cross-sections, the width and thickness has a greater influence on the resin impregnation speed. When the resin liquid flow from the large cross section (the wide end and thick end) to the small cross section (the narrow end and thin end), its resin impregnation speed is faster than that in a fiber perform with constant cross section. When the resin liquid flow in a inverse direction, the speed is slower.When the fiber preform widened along the impregnation direction, more filling time is needed as the location getting farther away from the injection gate.When the resin flows from the small cross section to the large one, the slowdown effect of the small cross section can be reduced with the assistant of the distribution medium.3. The permeability of the12k carbon fiber unidirectional fabric preform was measured to be1.39×10-12m2using athe vacuum bagging method, one order of magnitude lower than that of the glass fiber unidirectional fabric preform (1.35×10-11m2), and the permeability of the mixed glass and carbon fiber preform is between them.When the glass fiber is on the carbon fiber, the permeability is bigger, and when the glass fiber and carbon fiber is more uniform, the permeability is bigger.4. Preliminary exploration and study of the application of VIMP on one step integral forming of the composite multi-walled structure was also constructed.