Implementation of a viscoelastic material model to predict the compaction response of dry carbon fiber preforms

Determining the compaction behavior of fibrous material is essential for fiber reinforced composites manufacturing processes. The compression state directly influences both fiber volume content and tooling forces in closed mold processes. In this work, we present a viscoelastic material model which describes the compaction stress response. In its incremental formulation, the model is implemented into a finite element code, which makes it possible to calculate the thickness of force-controlled setups. We derived model parameters from compaction experiments with woven and non-crimp fabric carbon fiber preforms. The predicted compaction stress for both materials was in good agreement with the experimental data. Moreover, the model is capable of predicting creep and spring back behavior for force-controlled experiments. We proved that the developed model can be used to eliminate peak stresses during compaction and is also capable of predicting the time-dependent thickness response by means of a single set of formulas.