A SERVICE OF

logo

Open as PDF
next previous
PREDICTION OF ELASTIC CONSTANTS AND THERMAL EXPANSION
5-21
5.2.2 Geometry
Defining the geometry of a textile composite in sufficient but not overwhelming
detail is one of the most challenging tasks in its analysis. Various approaches have been
implemented in the computer codes (Table 5.4).
Units Cells
Several codes use unit cells to describe textile geometry for both quasi-laminar
and nonlaminar cases, since a periodic textile may be either quasi-laminar or nonlaminar.
If the textile is quasi-laminar, then the unit cell may be defined to lie entirely within one
ply or to span the whole thickness (Fig. 5-11). The former choice is strictly valid only if
all layers are exactly equivalent, which can only be true if the textile is also 2D (Section
2). But since the volume fraction of through-thickness fibers is always relatively small in
a quasi-laminar 3D textile, it is often a good approximation to regard such a structure as
layers of mainly in-plane fibers that are equivalent in the elastic regime. Choosing a unit
cell that spans the whole thickness will generally allow more detailed analysis. For
example, the effects of stacking layers with features in and out of registry can be studied
directly (Fig. 5-11b and 5-11c).