ASTM D3918-96
(Terminology)Standard Terminology Relating to Reinforced Plastic Pultruded Products
Standard Terminology Relating to Reinforced Plastic Pultruded Products
SCOPE
1.1 These definitions cover terms used in the reinforced plastics pultrusion industry. In some cases the terms may be identical to those employed in other standards or by other standards bodies.
Note- There is no similar or equivalent ISO standard.
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Designation: D 3918 – 96
Standard Terminology Relating to
Reinforced Plastic Pultruded Products
This standard is issued under the fixed designation D 3918; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope concave surface—a local concave curvature in the flat sur-
faces of pultruded plastic parts as measured transversely to
1.1 These definitions cover terms used in the reinforced
their length.
plastics pultrusion industry. In some cases the terms may be
convex surface—a local convex curvature in the flat surfaces
identical to those employed in other standards or by other
of pultruded plastic parts as measured transversely to their
standards bodies.
length.
NOTE 1—There is no similar or equivalent ISO standard.
crack—a visual separation that occurs internally or penetrates
down from the pultruded surface to the equivalent of one full
2. Terminology Definitions
ply or more of reinforcement.
black marking—black smudges on the surface of the pul-
crater—a small, shallow pultrusion surface imperfection.
truded product that cannot be removed by cleaning or
craze—multiple fine cracks at or under the pultruded surface.
scrubbing or wiping with solvent.
craze, hairline—multiple fine pultrusion surface separation
cracks that exceed ⁄4 in. (6.4 mm) in length and do not
NOTE 2—Black marking results from excessive pressures in the die
penetrate in depth to the equivalent of full ply of reinforce-
when the pultrusion is rubbing against soft or unchromed die surfaces.
ment.
blister—a rounded elevation of the pultruded surface with
craze, resin—multiple fine separation cracks at the pultruded
boundaries that may be more or less sharply defined.
surface not penetrating into the reinforcement.
NOTE 3—The rounded elevation somewhat resembles in shape a blister
NOTE 6—This condition is usually due to resin shrinkage during cure in
on the surface of human skin. Blisters may exist within the pultrusion as
resin-rich areas.
a hollow delaminated area (usually gas-filled) under a raised portion of the
surface.
craze, star—multiple fine pultrusion surface separation cracks
exceeding ⁄4 in. (6.4 mm) in length but not penetrating in
blooming, fiber—a pultrusion surface condition exhibiting a
depth to the equivalent of a full ply of reinforcement, that
fiber prominence or fiber show that usually has a white or
appear to emanate from a central point.
bleached color and a sparkling appearance.
NOTE 7—This condition is often caused by impact damage.
NOTE 4—The surface generally feels rough when touched by the fingers
and is of superficial thickness easily removed by buffing or light sanding.
delamination—the separation of two or more layers or plies of
reinforcing material within a pultrusion.
blooming, undercure—a dull and bleached surface color that
die-parting line—a lengthwise flash or depression on the
is evident in pultruded material not exposed to the weather.
surface of a pultruded plastic part.
NOTE 5—This condition is usually the result of insufficient surface cure.
NOTE 8—The die-parting line is associated with the area where separate
bow—a condition of longitudinal curvature in pultruded parts.
pieces of the die join together to form the cavity.
burn—a discoloration, distortion, or destruction of the pul-
discoloration—a streak or other pattern on the surface that
truded surface as a result of thermal decomposition.
causes a noticeable change of color from the rest of the
chips—minor damage to the pultruded surface that removes
pultruded surface.
material but does not cause a crack or craze.
dry fiber—a condition in which fibers are not fully encapsu-
lated by resin during pultrusion.
dullness—a lack of normal pultruded suface gloss or shine.
These definitions are under the jurisdiction of ASTM Committee D-20 on
Plastics and are the direct responsibility of Subcommittee D20.18 on Reinforced
NOTE 9—This condition can be caused by insufficient cure locally or in
Thermosetting Plastics.
large areas, resulting in the dull band created on a pultruded part within the
Current edition approved Nov. 10, 1996. Published May 1997. Originally
die when the pultrusion process is interrupted briefly (see stop mark).
published as D 3918 – 80. Last previous edition D 3918 – 80 (1990).
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 3918
dwarf width—a condition in which the crosswise (of the insufficient cure—a pultrusion abnormality created by lack of,
direction of pultrusion) dimension of a flat surface of the part or incomplete, cross-linking of the resin.
is less than that the die normally would yield for a particular
NOTE 18—This condition can usually be detected by dull surface
composite.
appearance, low Barcol hardness, and low physical properties. Thick
sections, cured from the outside in, can reveal insufficient cure in the
NOTE 10—This condition is usually caused by a partial blockage of the
center of the section even though completely cured on the surface. This
pultrusion die cavity caused by “build-up” or particles of the composite
condition can be caused by insufficient die temperature, improper catalyst,
adhering to the cavity surface. This condition is commonly called a “lost
or pulling too fast for the die temperature.
edge” when the flat surface has a free edge that is altered by the build-up.
intermittent disfigurement—disfigurement of the shape of
exposed underlayer—the underlying layer of mat or roving
the pultrusion for a limited length.
not covered by surface mat in a pultrusion.
NOTE 19—This condition usually results from die fouling or from
NOTE 11—This condition can be caused by reinforcement shifting, too
folded or crowded reinforcing material and is corrected after a short
narrow surface mat, too wide underlying mat, uneven slitting of surface
distance.
mat, or necking down of surface mat or excessive tension in pulling it off
the spindle.
internal shrinkage cracks—longitudinal cracks in the pultru-
fiber bridging—reinforcing fiber material that is found bridg-
sion that are found within sections of roving reinforcement.
ing across on an inside radius of a pultruded product.
NOTE 20—This condition is caused by shrinkage strains during cure
that show up in the roving portion of the pultrusion where transverse
NOTE 12—This condition is caused by shrinkage stresses around such a
strength is low.
radius during cure.
fiber prominence—a visible and measurable pattern of the lack of resin fillout—a pultrusion condition where an area
reinforcing material on the surface of a pultruded plastic contains reinforcement not wetted with sufficient quantity of
part. resin.
fiber show—strands or bundles of fibers that are not covered
NOTE 21—This condition usually occurs at
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