Compression and Relaxation Behavior of Dry Fiber Preforms for Resin Transfer Molding

Abstract

Compression and relaxation behavior of various fiber preforms for resin transfer molding was investigated experimentally through compression, relaxation, and decompression procedures. A simple Maxwell model was used in order to predict the nonlinear compression and relaxation behavior, and numerical simulation was performed for a unit cell of the fiber preform by using the finiteelement method. As the fiber volume fraction is larger than 0.4, compressive stresses acting on the woven fabric increased linearly with increasing fiber volume fraction. A typical hysteresis occurred due to relaxation behavior of the fiber preform during compression and decompression test. It was also found that numerical analysis yields slightly lower displacement field than experimental results under the same compressive force. However, experimental results were in good agreement with the analytic results obtained by considering the viscoelasticity of fiber preforms.

Analysis of a two-way tension-shear coupling in woven fabrics under combined loading tests: Global to local transformation of non-orthogonal normalized forces and displacements

“…The normalized resultant shear force of the shear motor (N 3s Þ can be found based on its global value, as shown in Eq. (11), where w refers to the clamping width (here 90 mm). Furthermore, Eqs.…”

“…One of the key benefits of these processes is the use of fiber preforms which makes it possible to pre-form the part apart from the molding cycle [5], resulting in faster process optimization trials. This preforming/draping stage has a significant influence on the subsequent resin flow impregnation and effective permeability [6][7][8][9], and hence characteristics of the final part [10][11][12][13]. Given the good conformability of woven fabrics, manufacturers today aim at applying these reinforcements to complex 3D shapes containing corners and double curvatures.…”

Modelling the viscoelastic stress relaxation of glass fibre reinforcements under constant compaction strain during composites manufacturing

“…Other researchers such as [14,15] have also employed Maxwell models to simulate stress relaxation and validated them using their experimental data, but the details are not readily apparent from the published results. There is thus a need for a model to adequately describe the stress relaxation response of a variety of glass fibre reinforcement materials, and this paper seeks to address that.…”

Modeling the viscoelastic compaction response of 3D woven fabrics for liquid composite molding processes

“…Several different approaches were used to model the viscoelastic behavior, the most common approach was to use empirical relations 12,13,25,26 with generalize Maxwell model, or various combinations thereof to represent the viscoelastic behavior. Authors such as Kim et al, 27 Kelly et al, 10 Muliana and Khan, 28 Echaabi et al, 29 Lee et al, 30 Haddad, 31 and Kim et al 27 used a model containing Maxwell elements in parallel (known as the Maxwell-Wiechert model) to simulate stress relaxation after compression of various dry reinforcements. Bickerton et al, 7 Kelly et al, 10 Somashekar et al 32 studied extensively the viscoelastic behavior of glass fiber reinforcements during an LCM process.…”