Abstract
Resin transfer modeling(RTM) is one of the most promising techniques for manufacturing high-performance fiber-reinforced composites (FRP) with respect to cost. In RTM, the permeability/porosity ratio of the fiber preform inside the mold is a critical process parameter, which varies with the geometric formation of the fiber reinforcement. This parameter dominates the property of resin flow and hence influences the final product quality. Various measurement systems have been developed for permeability estimation. However, most of them assume that the material porosity is a constant and estimate the permeability of the entire fiber perform as a single value, while the local variations are often ignored. In this work, a measurement system is developed to estimate the local values of the permeability/porosity ratio in RTM, which does not require to mount a large number of pressure semsors in the mold to obtain the local pressure gradients. Instead, at each sampling time point, the equivalent permeability/porosity ratio of the fiber preform between the injection gate and the flow front is calculated using Darcy's law. In the formula, the pressure difference along the flow path is known when the constant-pressure injection is employed, while the position of the flow front is acquired by a visualization system, Then, the local ratio can be derived based on the relationship between the equivalent values and the local ones. The feasibility of the proposed method is illustrated eith the experimental results.