Compaction of woven-fabric preforms: nesting and multi-layer deformation

In a previous paper the authors studied the elastic deformation during the compaction of a single-layer woven-fabric preform in liquid-composite molding (LCM) processes. This paper presents the analytical results for the nesting and elastic deformation during the compaction of multi-layer woven-fabric preforms. A 3-D model of the unit cell for multi-layer fabrics has been proposed with certain assumptions and has been adopted to predict the compressive behavior of yarns. On the basis of this model and beam theory in the mechanics of materials, analytical expressions for relationships between the fiber volume fraction, the applied compressive force, and the preform thickness reduction have been established for non-nesting and maximum nesting cases. For the general nesting cases, an empirical relationship between the compressive force and the thickness reduction is proposed.