Definitions /Dictionary/Glossary - nptel

Autoclave molding: A molding technique in which an entire assembly (lay-up) is placed into an
autoclave at 50 to 100 psi, in order to consolidate layers of the part by removing entrapped air
and volatiles. Usually includes application of heat to trigger curing of the resin.
Axial winding: A type of filament winding in which the filaments are parallel to the axis.
B-stage: Intermediate stage in the polymerization reaction of thermosets, following which
material will soften with heat and is plastic and fusible. It is also called resistal. The resin of an
uncured prepreg or premix is usually in B-stage. See A-Stage and B-Stage.
Bag molding: A technique in which the composite material is placed in a rigid mold and covered
with a flexible bag, with pressure applied by vacuum, autoclave, press, or by inflating the bag.
Balanced laminate: All lamina except those at 0/90 are placed in plus-minus pairs (not
necessarily adjacent) symmetrically about the lay-up centerline.
Bearing strength: It is the maximum bearing stress that will not cause a composite to fail when
applied through a cylindrical fastener surface.
Bearing stress: Applied load divided by bearing area (hole diameter times thickness).
Bias fabric: A fabric in which warp and fill fibers are at an angle to the length.
Biaxial winding: A type of filament winding in which the helical band is laid in sequence, side
by side, with no crossover of the fibers.
Bidirectional laminate: A reinforced plastic laminate in which the fibers are oriented in more
than one direction in the plane of the laminate.
Bismaleimide: A type of polyimide that cures by an addition reaction, avoiding formation of
volatiles, and has temperature capabilities between those of epoxy and polyimide.
Bleeder cloth: A layer of woven or non-woven material, not a part of the composite, that allows
excess gas and resin to escape during cure.
Bleed-out: The excess liquid resin appearing at the surface, primarily during filament winding.
Bond strength: The amount of adhesion between bonded surfaces. As measured by load/bond
area, the stress required to separate a layer of material from that to which it is bonded.
Boron fiber: A fiber usually of a tungsten-filament core with elemental boron vapor deposited
on it to impart strength and stiffness.
Braiding: Weaving fibers into a tubular shape.