MIL-DTL-62474F
sizing is used, the fabric shall be cleaned (scoured) to a maximum content of 0.5 weight percent
of the moisture-free fabric weight. The maximum moisture content of the aramid fabric after
weaving or weaving and scoring shall be five (5) percent by weight as determined by ASTM
D629, Section 9. Fabric quality shall conform to paragraph 3.3 of AMS 3902. Selvages shall be
woven or three-end leno. Tension in warp and fill shall be adequate to assure uniform fabric
construction after resin coating/impregnation (see 4.4).
3.2.2 Laminating resin. The resin for coating and laminating the aramid fabric laminate
shall be a catalyzed system composed of a mixture of phenol formaldehyde and polyvinyl butyral
resins. Resin coating of the fabric shall be uniform and accomplished by continuous
preimpregnation of the fabric. Moisture content of the aramid fabric shall be determined in
accordance with Section 9 of ASTM D629. The sample shall be dried until the loss in mass is
reduced to less than two (2) percent prior to resin coating. Resin content of the class C aramid
laminate after coating shall be 18 to 22 weight percent solids (volatile free) based on the weight
of aramid fabric as determined by ASTM D3776 (option C) with moisture content reduced to
less than 2 percent. Resin content of the class D aramid laminate after coating shall be 12 to 18
weight percent solids (volatile free) based on the weight of aramid fabric as determined by
ASTM D3776 (option C) with moisture content reduced to less than 2 percent. NOTE: A
sample of resin coated fabric that has been placed in a forced air circulating oven at 330 +10
degrees Fahrenheit (°F) [154 +6 degrees Celsius (°C)] for 60 minutes is considered to be volatile
free (see 4.4).
3.2.3 Recycled, recovered, or environmentally preferable materials. Recycled,
recovered, or environmentally preferable materials should be used to the maximum extent
possible provided that the material meets or exceeds the operational and maintenance
requirements, and promotes economically advantageous life cycle costs.
3.3 Construction (fabrication).
3.3.1 Dimensions and structure. The plastic laminates shall be of the dimensions stated
in the acquisition documents (see 6.2). The class A and B laminates shall consist of the specified
number of plies of resin-coated aramid fabric reinforcement bonded together in a single molding
step with heat and pressure. The laminates shall be built up from individual plies of fabric with
no fabric gap or selvage in any individual ply (see 4.3.3 and 4.4). Class C and D laminates shall
consist of whatever number of plies required for the specified areal density of the finished
laminate.
3.3.1.1 Thickness and flatness variation. The thickness at any point more than one in.
from an edge shall not vary from the nominal thickness of the panel by more than +0.015 in.
(0.38 mm) for type I and +0.030 in. (0.76 mm) for type II. Variation from flatness for each
finished panel shall not exceed 0.06 inch per foot (in/ft) (5.00 millimeters per meter (mm/m)
(See 4.3.3 and 4.4).
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