Abstract
A model, based on the Van Wyk model, is developed to predict the compaction behaviour of stack sequence of dry fabric plies, and is used a set of 3 parameters (stiffness k, pressure sensitivity n and initial fibre ratio Vf0) with P = (k(Vf- Vf))n. The method originality is to construct the behaviour law of a complex stack sequence by the assembly of elementary behaviours. Elementary behaviours are identified using initial experimental compaction tests and are linked to the interaction of a fabric ply with its surrounding environment (another fabric ply or the surface of the compressive mould). This proposed modelling approach have been tested on various carbon, flax and carbon/flax hybrid stack sequence, and seems efficient to predict their compaction behaviour. Its validity is limited to the range of stack sequence of a reduced number of plies. With stack sequence made of numerous fabric plies, some new phenomena must be taken into account. In complement we proposed a method to decompose the compaction behavior curve into three stages (rigid body movement of the fabric plies, nesting of the plies, densification). This method is relevant to compare easily some compaction curves and to evaluate the internal strain state of a stack sequence.
Highlights
With the new legislations for more environmentally friendly materials, composite reinforcements made from plant fibres, especially flax fibre, have been developing significantly
As the pressure is limited to 6 bars during the compaction test, the mechanisms involved into the deformation of the layer stack are mainly caused by rigid body movements like nesting and tow flattening, while deformations of elementary constituents of fabric layer are still weak
Elementary behaviours are identified using a first set of experimental compaction tests and are linked to the interaction of a fabric layer with its surrounding environment
Summary
With the new legislations for more environmentally friendly materials, composite reinforcements made from plant fibres, especially flax fibre, have been developing significantly. The hybridization of these reinforcements with some conventional synthetic fibres is a current trend [1,2,3,4,5,6,7]. The compaction of fabric stack before or during their impregnation with a polymer matrix is a crucial key-point of the control of the manufacturing process and of the future technical properties of the consolidated composite [8]. The last section is devoted to a proposition of decomposition method of the parameters of the compaction model as a function of the stack sequence
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