Graphite is an "anisotropic" material, meaning the stiffness and strength properties are greater in the fiber direction than they are in any other direction. For most graphite shafts, the base material is a sheet of unidirectional (UD) prepreg in which the carbon fibers are all oriented in the same direction. Parts made of UD prepreg have high stiffness and strength in the fiber's direction, but little stiffness or strength in any other direction.
The "Interlinked Carbon" material as in the Frequency Filtered putter shaft and IROD shafts is not unidirectional, but biaxial. In this prepreg, the carbon fibers are grouped together in tow sizes of 3K (3,000 individual fibers per bundle). These tows are woven together in a weave commonly referred to as 'plain weave' in which an equal number of 0-degree and 90-degree tows are interlaced over and under each other in an alternating fashion, giving its distinct appearance.
Everyone knows that golf shafts flex and oscillate along their axis. However, some flexing or deformation also occurs around the shaft's circumference. During a golf swing, the normally round shaft becomes more oval as it is loaded. This phenomenon is more prevalent in the shaft's butt section, where the diameter is larger and the walls are thinner. When this deformation occurs, the golfer perceives this as a weaker, less stable feeling in the shaft.
Most shafts are made from unidirectional prepreg, with the fibers placed along the shaft's axis for stiffness. Other plies of unidirectional prepreg are placed at an intermediate angle (usually 45°) to the shaft axis to keep the torque low. But with no fiber in the "hoop" direction (around the shaft's circumference), the hoop strength is low and deformation occurs.
In the Frequency Filtered putter and IROD shafts, UST Mamiya uses its "Interlinked Carbon" in the butt section to offset the weakening effect. Half of the "Interlinked Carbon" fibers are in the same direction of the shaft's axis help provide stiffness in the hands. The other half are in the circumferential direction, adding to the shaft's hoop strength, keeping it more round throughout the swing. Using Interlinked Carbon in the butt section offers superior control and stability in the hands. The weave style of this material also offers a classy look to the shaft, giving the customer visible proof that the technology is working in their favor.