Compressibility and flow permeability of two-dimensional woven reinforcements in the processing of composites

The processing of composites under pressure is described by a viscoelastic model in which the pressure acts on the fibers in an elastic manner and on the liquid matrix in a viscous manner, Following a micro-mechanics approach, an analytical model has been derived for the nonlinear elastic compression of two-dimensional, orthotropic, plain woven fiber cloths, containing two empirical constants. The model is validated by experimental data and the empirical constants determined in the compression of a wet, plain woven, glass fiber reinforcement. The effects of the compression of woven cloths during processing are demonstrated by the change of their permeability.