The effect of shear deformation on the processing and mechanical properties of aligned reinforcements

Permeability of non-crimp fabric preforms

“…The two leading types of deformation are compression of the textile reinforcement and shear deformation. The effects of both are investigated experimentally by a number of researchers (Chen et al , 2001;Endruweit and Ermanni, 2004;Govignon et al , 2010; © Woodhead Publishing Limited, 2011 Heardman et al , 2001;Lai and Young, 1997;Loendersloot, 2006;Louis and Huber, 2003;Schuster et al , 2008;Smith et al , 1997;Stadtfeld et al , 2002).…”

“…This simplifi ed approach allows for an estimation of the orientation of the principal permeabilities and the anisotropy, as proposed by Advani et al (1994): [8.9] With K x and K y the longitudinal and transverse permeability of a unidirectional ply of fi bres, θ the ply orientation and γ the shear angle. The transverse permeability is generally small compared to the longitudinal permeability (Gebart and Lidström, 1996;Smith et al , 1997): K y << K x . The anisotropy α can then be approximated by discarding the contribution of K y : [8.10] Experimental results show deviations to this (simplifi ed) theoretical approach, which can be attributed to the presence of the stitching.…”

Understanding variability in the permeability of non-crimp fabric composite reinforcements

“…While considerable efforts have been made to develop formulations for, in particular, the effect of drape on the fabric's properties (e.g. Smith et al , 1997), variations due to external infl uences and quality issues are case-specifi c and cannot be discussed in a generalised way.…”

Multiscale modeling of combined deterministic and stochastic fabric non-uniformity for realistic resin injection simulation

“…Regarding deterministic fabric non-uniformity, the mechanics of fabric drape, 1,2 simulation of drape 3 and the effect of drape on the (local) fabric permeability [4][5][6][7] are discussed extensively in the literature. To address the issue of variability in resin flow patterns caused by stochastic local variations in fiber orientation and fiber volume fraction, Lundströ m et al 8 derived non-uniform local fabric permeability values from variable dimensions of interyarn flow channels.…”

“…In equations (4) and (5), N was set to a value of 6 as a compromise between accurate reproduction of the distribution of frequencies and computational efficiency. The choice of terms in the expansions implies that the waviness along the yarn directions determines the scale of variation perpendicular to the yarns as well.…”