A nonlinear compaction model for fibrous preforms

Based on the mechanics of porous media and physical insight gained from exp erimental observation, a model for predicting the nonlinear compaction of f ibrous preforms in the resin transfer molding process is developed. A key p hysical constant - namely, preform bulk compressibility - is proposed to es tablish the relationship between the applied pressure and the preform bulk volume. The preform bulk compressibility is a function of fiber volume frac tion and five parameters - the initial fiber volume fraction, the final (ma ximum attainable) fiber volume fraction, the initial pore volume compressib ility, the fiber compressibility, and an empirical index. Results of compac tion experiments on plain-woven fabric preforms and unidirectional non-wove n materials support the validity of the model. Excellent agreement between theory and experiments has been obtained. The present model provides for fi brous preforms a nonlinear constitutive law whose coefficients can be physi cally interpreted. (C) 2001 Elsevier Science Ltd. All rights reserved.