Page 90 - 3D Fibre Reinforced Polymer Composites

Micromechanics Models for Mechanical Properties 79
each individual laminate slice, which are determined by considering the presence of
fibre undulation.

Figure 4.7 Slice array model for unit cell of plain weave: (a) Unit cell of plain weave
lamina, (b) actual slices along y coordinate of the unit cell, (c) idealised slices for the
actual slices (Naik and Ganesh, 1992)

It is assumed that the yarn cross-sectional shape is uniform and the fibres in the yarn are
undulated only in the longitudinal direction. To describe the uniform cross-sectional
shape, as shown in Figure 4.7(a), four parameters are used to define the length
0.5(aw+gw) and width 0.5(a+gf) of the unit cell, and three parameters are used to define
the thickness of the unit cell 0.5h,,,+h+hW+0.5h,. Based on the uniform cross-sectional
shape assumption, it is clear that the height of the weft is a function of only y and the