Definitions /Dictionary/Glossary - nptel

Bi-directional: Reinforcing fibers arranged in two directions, usually at right angles.
Bi-directional Laminate (Cross Laminate): A reinforced plastic laminate whose fibers are
oriented in two directions in its plane.
Binder: Coating which is applied to the surface of a chopped glass mat or preform and then
cured to hold bundles or ends together in a stable form during the roving operation.
Birdnest: A large, tangled up collection of continuous glass bundles unable to run through the
guide eye into roving creel. In the field, it can also be a large tangled collection of roving which
does not run through the tube or guide eyes to the chopper.
Bismaleimide (BMI): A polyamide that cures through an addition rather than a condensation
reaction, thus avoiding problems with volatiles forming. It is produced by a vinyl-type
polymerization of a pre-polymer terminated with two maleimide groups. BMI has an
Intermediate temperature capability (between epoxy and polyamide).
Bisphenol A: A condensation product formed by the reaction of two molecules of phenol with
acetone (A). This polyhydric phenol is a standard resin intermediate along with epichlorohydrin
in the production of epoxy resins.
Blade Packing: Glass bundles or chopper fuzz which build up and pack between the blades of a
chopper. Blade packing can result in poor choppability. If it falls off, it usually does not wetthrough,
causing blisters or porosity.
Blanket: Fiber or fabric plies that have been laid up in a complete assembly and placed on or in
the mold all at one time (flexible bag process). It is also, the form of bag in which the edges are
sealed against the mold.
Bleeder Cloth: Woven or non-woven layer of material used in composite parts manufacturing
that allows excess gas and resin to escape during cure. The bleeder cloth is removed after the
curing process and is not part of the final composite.
Blister: Flaw either between layers of laminate or between the gel coat film and laminate.
BMC: Bulk Molding Compound (Thermoset).
Bobbin: The spool or shipping package on which textile yarns are wound.
Bond Strength: Amount of adhesion between bonded surfaces. The stress required to separate a
layer of material from the base to which it is bonded, as measured by load/bond area.
Boron Fiber: Fiber produced by vapor deposition of elemental boron, usually onto a tungsten
filament core, to impart strength and stiffness.