Experimental Study of Bending Behaviour of Reinforcements

Abstract

In composite reinforcement shaping, textile preform undergo biaxial tensile deformation, in plane shear deformation, transverse compaction and outof-plane bending deformations. Bending deformations have been neglected in some simulation codes up to now, but taking into account them would give more accurate simulations of forming especially for stiff and thick textiles. Bending behaviour is specific because the reinforcements are structural parts and out of plane properties cannot be directly deduced from in-plane properties, like for continuous material. Because the standard tests are not adapted for stiff reinforcements with non linear behaviour a new flexometer using optical measurements has been developed to test such reinforcements. This new device enables to carry out a set of cantilever tests with different histories of load. A series of tests has been performed to validate the test method and to show the capacities of the new flexometer to identify non linear non elastic behaviour.

Design and Potentiality of an Apparatus for Measuring Yarn/Yarn and Fabric/Fabric Friction

“…Several key entry parameters for the simulation models need to be determined. The mechanical properties of a fabric ply have been widely studied [10][11][12][13][14][15][16][17][18][19][20], and many teams are still working on this topic to refine the knowledge of the composite community. However, in addition to the ply properties, the fabric/tool contacts and, when dealing with multi-ply forming, the fabric/fabric contact have to be studied and modelled.…”

“…In addition, very different unit cell sizes and anisotropy also have to be dealt with. This suggests that specific experimental equipment should be considered to take into account these specifications [10][11][12][13][14][15][16][17][18][19].…”

Simulations of Composite Reinforcement Forming

“…Nevertheless this bending stiffness is important to obtain accurate wrinkle shape. Specific tests have been developed for these textile materials, the bending stiffness of which is much smaller than the one given by the plate theory (Kawabata, 1986, Lahey and Heppler 2004, de Bilbao et al, 2010. Figure 10 shows a cantilever bending test (de Bilbao et al, 2010).…”

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

“…Indeed, for structural application in the automotive or aeronautical industries numerous publications [24][25][26][27] study the mechanical characteristics and the deformability of carbon or glass reinforcements in conjunction to the manufacturing process. These studies concern the scale of tows, (fibre assemblies) and the scale of reinforcements (tow assemblies).…”

“…Up to now, the mechanical behaviours of the tows and fabrics have been mostly conducted on glass or carbon assemblies [24,25,27]. In this study, it is proposed to analyse the forming potentialities of a flax fibre based fabric, in the case of the sheet forming process associated to deformability studies at the scale of the tows and the fabric.…”