An experimental study of the influence of process parameters on the textile reaction to transverse impregnation

Abstract

When applying a transverse impregnation within a liquid composite molding process, the main goal is to decrease impregnation time by reducing flow path lengths within the textile. However, the pressure drops emerging during impregnation cause hydrodynamic compaction of the textile as well as a heterogenization of the fiber volume content distribution. Within this study a new approach for the description of such transverse impregnation behavior is presented and exemplarily shown for a woven and a noncrimp fabric. The starting point is a novel measurement system allowing an on‐line monitoring of flow‐induced compaction during permeability measurement. Using the system, the reaction of both textiles to various flow conditions in terms of pressure drop and flow rate was measured and expressed by a set of functions. These allow continuous interpolation and can be used e.g. as direct input for simulations or to validate existing models. For both textiles a severe reduction of the permeability with increasing pressure drop respectively flow rate was measured. Accordingly, it was found that with increasing injection pressure the flow rate can stagnate or even decrease. Knowledge about such behavior is required for process and tooling optimization concerning cycle‐time and cost‐efficiency. POLYM. COMPOS., 37:2820–2831, 2016. © 2015 Society of Plastics Engineers

An evaluation of the reproducibility of ultrasonic sensor-based out-of-plane permeability measurements: a benchmarking study

“…Several studies have shown an influence of injection pressure. Becker et al 35 verified experimentally for the glass fiber woven fabric used in this study, that this influence is also given at low injection pressure in combination with high pre-compaction. Additionally, the deformability influence is an issue even if the same pressure drop is applied at both institutes.…”

Determination of the unsaturated through‐thickness permeability of fibrous preforms based on flow front detection by ultrasound

“…Drapier et al [21] NCF 6458 carbon 61 2.5 1.5 Scholz et al [22] 55-60 2.2-1.5 9.5-1.9 Ouagne et al [23] Woven carbon 50-55 50-25 12-1.6 Klunker et al [24] 20.5-9 Becker and Mitschang [25] Woven glass 50-55 7-1.5 6.6-3.8 Ahn [3] 35-1.2 Nedanov and Advani [7] 59 14.2 2.2 the injection pressures remain at levels that affect filling; getting measurements free from this affecting factor would produce unrealistic permeability values. Despite the fact that theoretically permeability is not dependent on injection pressure, in practice, pressure does have a measurable impact with respect to the compaction behavior (preform thickness) [25]. As such, the results obtained in this study do not characterize the preforms alone but the preforms with respect to specific injection pressures and layer number.…”

Impact of stitching on permeability and mechanical properties of preforms manufactured by dry fiber placement

“…The out‐of‐plane permeability measurements were performed with a system following a saturated principle (Fig. , ). The measurements were performed at a pressure drop of 1.0 bar.…”

“… Measurement system for out‐of‐plane permeability of dry fiber materials . [Color figure can be viewed at http://wileyonlinelibrary.com]…”