Unidirectional (UD) Fabrics
Unidirectional (UD) fabrics are fabrics in which most of the fibers operate in only one direction. Although the other fibers may provide some structural properties, the main fibers can be held in position, with a small amount of fiber or other material in other directions. Unidirectional fabrics generally take their primary fibers in the direction of 0 °, but may also have a roll length of 90 °.
True unidirectional fabrics allow the fiber component to be placed exactly where it is needed and in the optimum amount (more or less than required). In addition, the UD fibers are straight and unopened. This results in the highest possible fiber properties in a fabric in the composite component construction. For mechanical properties, unidirectional fabrics can only be developed with a pre-made unidirectional tape, which does not have a secondary material that holds the unidirectional fibers in place. In these prepreg products only the resin system holds the fibers in place.
In unidirectional fabrics, there is no gap between these flatly extending fibers. There is no sectioned mesh that separates the fabric fiber in two directions. Thus, the fabric has a higher shrinkage potential than the other fabrics towards the direction of the fibers. Approximately 3 times the steel corresponds to the tensile strength.
One-way reinforcement is ideal for applications where front-to-back strength is the most important. For example, in tubular structures moving only forward and backward, such as rockets, planes and boats, one-way carbon fiber is often used as reinforcement. One-way carbon fibers are used in the trunks to make the bicycles light and high-strength.