Influence of Fluid Properties on Transverse Fabric Compressibility During In-Situ Impregnation
Topic(s) : Material and Structural Behavior - Simulation & Testing
Co-authors :
Marcel BENDER (AUSTRIA), Ewald FAUSTER (AUSTRIA)Abstract :
Transverse compressibility of technical reinforcements e.g., woven or non crimp fabrics, was studied in detail on a theoretical and experimental basis, and recently the findings of an international benchmark exercise (IBE) on experimental characterization of transverse compaction characteristics was published [1]. This outlined a test program consisting of (i) a loading phase (constant speed to achieve set fibre volume fraction), (ii) a relaxation phase (maintaining this fibre volume fraction) and (iii) an unloading phase (opposite to the constant closing speed). Based on this test program two glass fibre fabrics, a woven and a non-crimp fabric, were characterized by the participants in both, a dry and a saturated state. In order to ensure comparability, a guideline was provided that describes the method for reaching the so called ex ante saturation. This guideline contained a detailed description of the immersion process for the test specimens, the immersion time and the subsequent dripping of excess fluid. As a result of this saturation scheme, a squeeze flow effect occurred during the loading and relaxation phase forcing out surplus fluid, which influenced the wet compaction characteristics.
Based on the results of this IBE, a novel test setup was developed, which allows for a simpler, more reproducible experimental characterisation of the dry and wet compressibility characteristics by applying a new in situ impregnation method [2]. The work at hand utilizes this in situ test method, a woven and a non crimp glass fibre fabric with comparable fibre areal weights (FAW) and eight different test fluids to analyse the fluid influence on the measured compressibility characteristics. As initial tests have shown that the viscosity of the liquid is not the only significant parameter, the test liquids covered a wide range from water to almost honey-like viscosities as well as polar and non-polar liquids.
The results are compared in terms of maximum and final compaction load (Figure 1, marker 1 and 4, respectively), but also in terms of load change during in situ impregnation (Figure 1, phase from marker 2 to 3). In addition, the time to an equilibrium load during impregnation as well as during wet relaxation is analysed. An attempt is made to reflect the recorded material characteristics in an extended material model and to identify fluid properties impacting the fabric compaction behaviour.
Figure 1: Schematic in-situ impregnation method and characteristic points during the test [2].
Based on the results of this IBE, a novel test setup was developed, which allows for a simpler, more reproducible experimental characterisation of the dry and wet compressibility characteristics by applying a new in situ impregnation method [2]. The work at hand utilizes this in situ test method, a woven and a non crimp glass fibre fabric with comparable fibre areal weights (FAW) and eight different test fluids to analyse the fluid influence on the measured compressibility characteristics. As initial tests have shown that the viscosity of the liquid is not the only significant parameter, the test liquids covered a wide range from water to almost honey-like viscosities as well as polar and non-polar liquids.
The results are compared in terms of maximum and final compaction load (Figure 1, marker 1 and 4, respectively), but also in terms of load change during in situ impregnation (Figure 1, phase from marker 2 to 3). In addition, the time to an equilibrium load during impregnation as well as during wet relaxation is analysed. An attempt is made to reflect the recorded material characteristics in an extended material model and to identify fluid properties impacting the fabric compaction behaviour.
Figure 1: Schematic in-situ impregnation method and characteristic points during the test [2].