In applications in which high shear strength and impact resistance are desired, carbon fiber is often reinforced with other materials, such as Kevlar^®. This material consists of long molecular chains produced from poly-paraphenylene terephthalamide. The molecules are highly ordered by being held in place by Van der Waals forces (the dotted lines in the figure). Exceptionally difficult to cut and machine, requiring carbide tools and great skill, Kevlar^® is one of the strongest materials known to man.  It has found use in applications where light weight and high tensile strength are required.  Secart uses only aerospace grades of Kevlar® in all of its products.