UD stands for ‘unidirectional’: in Dyneema® UD all the fibers are laid
parallel, in the same plane, rather than being woven together. Dyneema® UD is
made of several layers of Dyneema® fibers, with the direction of fibers in
each layer at 90° to the direction of the fibers in the adjacent layers. The
unidirectional configuration of the fibers in Dyneema® UD allows the energy
transferred from the impact of a bullet or other threat to be distributed
along the fibers much faster and more efficiently than in conventional woven
fabrics. This is because the absorption power of the yarn in woven fabrics is
lost at the crossover points, as these points reflect rather than absorb the
shockwaves of the impact. In Dyneema® UD, much more of the material is engaged
in stopping the bullet, making it more effective against ballistics.
Dyneema® UD is available in two types: