The primary reinforcement I use in my boards is Vectorply E-TLX 2200, which is a stitched triaxial E-Glass. 54% of the fibers run in the longitudinal direction (0 degrees) while the other 46% of the fibers are evenly divided between the 45 and -45 degree directions. The fibers are stitched together in three layers, rather than being woven like tradition fiberglass, which is what most of us are familiar with.
I greatly prefer non-woven fabrics for snowboard and ski applications. Weaving causes stress points everyplace a bundle of fibers crosses over or under another bundle. The constant flexing of a snowboard causes a rapid breakdown of the resin around these stress points, leaving the fibers unsupported and thus prone to breaking. Board built with woven fabrics lose their stiffness far more quickly than we find acceptable. Stitched fabrics allow the fibers of each layer to lay flat on top of each other yielding a stronger laminate over time. Further, stitched fabrics trap less resin than woven, resulting in a lighter laminate.
In addition to the fiberglass, I use Kevlar and carbon fiber in various places. Every board gets a very light weave of Kevlar backing the inserts. And, yes, having just explained why woven fabrics are bad in snowboards, this small application of such a light Kevlar weave is alright in this area as it receives so little flex. A patch of Kevlar which the inserts are pushed through provides stronger insert retention, and greatly reduces “binding suck”, that phenomena where the base underneath the bindings tends to suck in to the core when the bindings are tightened.
Unidirectional Kevlar or carbon is used on some boards to provide extra stiffness and pop depending on the application. An especially large board might be reinforced with Kevlar strips along the base to help provide stiffness while keeping the core thinner, and thus reducing weight. Kevlar or carbon may be used in just the nose or tail section, or spread between the bindings and the nose or tail in order to give more torsional rigidity. I use 1” wide unidirectional Kevlar and carbon fiber, and in some applications many very thin strips of carbon roving.