Rheological models for modeling the viscoelastic behavior in liquid composite molding processes (LCM) review

In recent years, a crucial interest has focused on closed mold composites manufacturing technologies. Mainly due to the ability to handle the harmful emissions of hazardous gases and the ability to produce parts with complex geometry. The liquid composite molding term includes a list of manufacturing composite varieties, such as resin transfer molding, vacuum assisted resin transfer molding, compression resin transfer molding. All liquid composite molding varieties involve compressive strain reinforcement before and in many cases during mold filling. The compressive strain reinforcement response is generally considered as non-linear elastic for the modeling. The viscoelastic stress relaxation is thus taken into account. A better understanding of the compressibility phenomenon helps to improve control of implementation process of parts and tooling design. The quality of the parts can also be improved through a better understanding of the stresses acting in composite products. In this paper, we present a detailed review of the most important models that have focused on the compression and relaxation of fiber reinforcements. In the order of succession, we first present the models giving a non-linear elastic behavior for fibrous reinforcements, then the models considering the reinforcements as viscoelastic materials.