All rights reserved. All rights reserved. Modulus of Fiber-Reinforced Composites Fibers have a very high modulus along their axis, but have a low modulus perpendicular to their axis. If the fibers are all parallel, the modulus of a fiber reinforced composite depends upon which direction you're measuring. E f is the modulus of the fiber along the length of the fiber.
V f is the volume percent occupied by the fibers.
Fiber composite manufacturers often rotate layers of fibers to avoid directional variations in the modulus. The fibers or yarns can either be woven into a loose mat of randomly oriented fibers or aligned into an unidirectional tape. The mat or tape is then placed against or around a mold or die and saturated with polymer chains to form what is known as a prepeg. The polymer chains must be in completely infiltrate around the reinforcing fibers to realize full reinforcing capability. Hot gases, a vacuum, a roller or opposing die puts pressure on the prepeg and forces the polymer chains to flow around the fibers.