ANALYTICAL METHODS FOR TEXTILE COMPOSITES
all directions. This pattern of reinforcement requires volumes of pure matrix material to fill
the substantial interstitial areas created by the fiber bundles. The problem of shaping and
arranging straight elements in several directions while maximizing the volume they occupy
is an interesting one [2.8].
Figure 2-15. 3D orthogonal composite.
The concept of multiple direction linear reinforcement can be extended to a larger
number of non-orthogonal fiber bundle orientations. These are termed nD materials (in a
somewhat loose use of the term dimension!) For example, a 4D material could be created
with fiber directions that connect the diagonal corners of a cube. There can be significant
strength advantages to using a 4D or 5D material when shear and multidirectional loading
are considered [2.9].
2.3.2 The relation of volume fraction and fabric geometry to process
parameters
The properties of textile composites depend most of all on the total volume fraction
of all fibers and the proportions of the fibers that point in various directions. These
characteristics can be predicted with useful accuracy by fairly simple models of the fabric
geometry.
2.3.2.1 2D Weaves
Crucial properties of a 2D weave include yarn paths, cross-sectional shapes, and
the pattern and geometry of exchange points. Calculations of these characteristics from
