Aramid: The generic name for “Kevlar”, which is a registered trademark of Dupont.

Breaking Strength: Measured in pounds per inch (lb./in.). The first number will be the breaking strength in the warp direction. The second will be the fill direction. Most fabrics are stronger in the warp than the fill because higher tension is placed on the warp fiber keeping it straighter during the weaving process. Rare exceptions occur when a larger, therefore stronger thread is used in the fill direction than the warp direction. Fabrics are generally considered ”balanced” if the breaking strength is within 15% warp to fill and are best in bias applications on lightweight structures. “Unbalanced” fabrics are excellent when a greater load is required one direction and a lesser load in the perpendicular direction.

Fill: The threads that run the width of the roll or bolt and perpendicular to the warp threads.

Finish: The chemical treatment to fiberglass making it compatible with resin systems, therefore improving the bond between the fiber and the resin. Finishing fiberglass typically decreases the fiber strength by as much as 50%. Both silane and volan finishes are epoxy compatible. Historically, volan has been considered a softer finish for a more pliable fabric, but recent advances have yielded some excellent soft silane finishes.

MSDS: Law requires Material Safety Data Sheets on some products. They will be supplied upon request via fax or mail.

Thickness: Measured in fractions of an inch. The thicker the fabric the more resin required to fill the weave to obtain a smooth finished part.

Thread Count: The number of threads (tow in carbon and yarn in Aramid) per inch. The first number will be the warp count and the second will be the fill count.

Tow: The bundle of individual carbon filaments used to weave carbon fabric. 50k tow means there are 48-50,000 carbon filaments in the tow. Smaller tow i.e. 12k, 6k, 3k and 1k are obtained by dividing the 50k tow into smaller bundles.

Warp: The threads that run the length of the roll or bolt and perpendicular to the fill threads.

Weaves: Plain weave means the warp and fill threads cross alternately. This is the most common weave. 4 Harness (4 HS Satin or crowfoot) weave means the fill thread floats over three warp threads, then under one warp thread. This weave is more pliable than the plain weave, therefore conforms to complex curves more easily. 8 Harness (8 HS Satin) weave means the fill thread floats over seven warp threads, then under one warp thread. This weave is the most pliable of the standard fiberglass weaves. 2 x 2 Twill weave means the fill thread floats over two warp threads, then under two warp threads. This weave is found most commonly in carbon fabrics and is more pliable than plain weave. See these diagrams.

Weight: Estimated in ounces per square yard (oz./sq. yd.).