Hydro-mechanical loading and compressibility of fibrous media for resin infusion processes

Abstract

The modelling of composite manufacturing processes where hydro-mechanical coupling takes place depends on the validity of compressibility and permeability models. In this work, the computer code initially used to simulate the effect of coupled hydro-mechanical load on composite preform (Ouahbi et al. Composites Part A, 38:1646-1654 is integrated into an inverse method to predict the compaction behaviour of the reinforcements. An experimental device developed at Le Havre is used to apply hydro-mechanical loads to the preforms. Two ramps of stress are imposed to the preform and the thickness evolution is measured as a function of time. The speed of thickness reduction is not constant and varies in the range of 0.1 to 12 mm/min. The effect of compression speed upon the saturated fabrics is investigated. For a fixed fibre volume fraction, an increase in stress is observed in increasing compression speed. The experimental results are compared to the compressibility curves determined by an inverse method. The calculated curves correspond to the compressibility curves experimentally obtained with low compression speed (∼0.25 mm/min). As a consequence, this suggests that a low compression speed should be applied when investigating the compressibility behaviour of composite preform with a view of modelling resin infusion processes.

Continuous measurement of fiber reinforcement permeability in the thickness direction: Experimental technique and validation

“…The permeability and the fabric deformation stress can be represented as a function of fiber volume fraction. (9) (10) Equation (10) is known as "Toll and Manson" equation which is an empirical relation between fabric compaction stress and fiber volume fraction [20,21]. In a similar way, the in-plane or transverse permeability values have also been related to fiber volume fraction by using a similar empirical power law model [22].…”

“…The identification procedure of fiber stress model coefficients has been described in the authors' previous work [21]. The model coefficients used in Equations (9) and (10) are listed in Table 1.…”

New methodology to determine the compressibility curve in a RIFT process

“…Other researchers [18][19][20] in their studies set an experimental device to impose hydro-mechanical loadings to fibrous preforms. Despite the fact that the device can be used to measure permeability and compressibility in a classical manner, its originality resides in the possibility of compressing the fibrous network at the same time as the fluid is injected through the fibres.…”

Mechanical characterisation of flax-based woven fabrics and in situ measurements of tow tensile strain during the shape forming

“…Some of the preforming defects such as wrinkling, may be the result of limit behaviour in a given deformation mode. The limit behaviour for each considered deformation mode can be identified for a given reinforcement independently of the process by in plane tests such as uniaxial and biaxial tension, in plane shear test [24][25][26] and by out of plane tests such as flexure [27] or compaction [38][39][40]. As an example, the wrinkle defects are generally associated to an in-plane shear limit angle above which they appear.…”