Compression and relaxation behavior of dry fiber preforms for resin transfer molding

Compression and relaxation behavior of various fiber preforms for resin transfer molding was investigated experimentally through compression, relaxation, and decompression procedures. A simple Maxwell model was used in order to predict the nonlinear compression and relaxation behavior, and numerical simulation was performed for a unit cell of the fiber preform by using the finite-element method. As the fiber volume fraction is larger than 0.4, compressive stresses acting on the woven fabric increased linearly with increasing fiber volume fraction. A typical hysteresis occurred due to relaxation behavior of the fiber preform during compression and decompression test. It was also found that numerical analysis yields slightly lower displacement field than experimental results under the same compressive force. However, experimental results were in good agreement with the analytic results obtained by considering the viscoelasticity of fiber preforms.