ANALYTICAL METHODS FOR TEXTILE COMPOSITES
reinforcing fiber bundle. In another process, the reinforcing yarns are coated with
thermoplastic powder.
Preform
To Vacuum
a) Resin Transfer Modling
Figure 2-8. Resin infusion techniques
2.2 Materials
Textile processes have been adapted to handle most of the fibers commonly used in
structural composites, including glass, aramid, and carbon. The only limitation to fiber
selection is that most textile processes subject yarns to bending and abrasion. Machines
have been modified to minimize fiber damage, but, in many processes exceptionally brittle
or stiff fibers cannot be used.
Important properties of some popular fibers are shown in Table 2.1, with the usual
assumption that they are transversely isotropic. Axial properties were obtained from
manufacturers' data sheets. The transverse properties have been estimated indirectly by
various techniques, since they cannot be measured by conventional mechanical tests. For
example, there is a relationship between the axial and transverse moduli of a carbon fiber,
which arises from the degree of alignment of the graphite crystals that make up the fiber.
Nonaxial properties can also be inferred by fitting micromechanical relations to the
measured transverse properties of composites.
