Mechanics of the squeeze flow of planar fibre suspensions
The authors examine axisymmetric squeeze flows of concentrated transversely isotropic fibre suspensions in a power-law matrix, and discuss the processing of composite materials such as sheet moulding compounds and glass mat thermoplastics (GMTs). To this end, an analysis of squeeze flow of an effective anisotropic power-law liquid between two approaching parallel plates is carried out, a solution is presented, and a variational approach is applied to the interpretation of squeeze flow behaviour. This gives a simple expression for the total pressure, which allows to separate the contributions due to extension and shear. The procedure is applied to GMT data, and it is noted that the dissipation is predominantly extensional except at very low plate separations. Then the authors give a detailed micromechanical analysis of the effective liquid itself based on a phenomenological drag law applied to the individual fibre tows, and derive a non-local constitutive equation. This is used to model the pressure distribution when the effective length of fibres is comparable to or determined by the dimensions of the squeeze flow plates. It is shown that the model describes satisfactorily observed squeeze flow stresses in both long and short fibre systems.
concentrated transversely isotropic fibre suspensions
scientific article; zbMATH DE number 1342563