Permeability and compaction behaviour of air-texturised glass fibre rovings: A characterisation study

Abstract

Air-texturisation is a process that adds bulkiness to bundles of fibres. In this study, the permeability and compaction behaviour of air-texturised glass fibre rovings are experimentally characterised and compared to conventional unidirectional rovings. Based on radial impregnation experiments and single-step compaction/decompaction tests, the following main findings are highlighted: Compared to conventional unidirectional-rovings, the normalised permeability of the air-texturised rovings was approximately three times higher along the fibre direction and 40 times higher transverse to the fibre direction. Accordingly, the degree of anisotropy was approximately one magnitude lower. At a compaction pressure of 1 and 5 bar, the air-texturised rovings were compacted to a volume fraction of [Formula: see text] and 0.43, respectively, which was approximately 30% lower than the volume fraction achieved for the conventional unidirectional-rovings. Finally, it was observed that the decompaction of air-texturised rovings exhibits a more distinct elastic response when unloaded.

Experimental study of roving configuration’s influence on the flow field in a full-scale transparent pultrusion injection box

“…Additionally, it emphasizes the importance of porosity as it can range through a multitude of scales based on external pressure, whereas higher pressures decrease porosity. 8,37 Even though pultrusion resins generally are considered to feature good wettability properties, capillary pressure is a material combination specific property, that needs to be evaluated for validity of specific resin fiber combinations.…”

“…35,36 Unfortunately, these permeability models are hard to validate or calibrate experimentally for the specifics of the pultrusion process. Due to that, permeabilities are often measured directly, 8,37 whereas it needs to be considered, that permeability measurements are method dependent. 38 Additionally, simulation model accuracy is limited by element size or calculation power, resulting in averaged material properties, which are not able to consider all relevant scales in the same model.…”

Revising testing of composite precursors – A new framework for data capture in complex multi-material systems

“…This is a typical example of model's overfitting and that was reported by numbers of researchers in various fields [32], [33]. Governing equations of high-performance consolidation models may contain complex over-parameterised terms and are able to fit any given data set [34], which may lead to overfitting of the training input sets [35]. In such a case, the underlying patterns and relationships of the experimental data are not captured by the algorithm.…”

Steady-state modelling and analysis of process-induced stress and deformation in thermoset pultrusion processes

“…In addition to the resin pressure, bulk compaction of the fibre material introduces a stress state when it enters the pultrusion die. For reference, based on the through-thickness compaction tests by Sandberg et al [53], a compaction pressure of approximately 7.5 bar (0.75 MPa) is needed to achieve the volume fraction of the test case (V f = 0.639, cf. Table 3).…”