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|  MIL-T-18847C(AS)
3.14.1.1 Filament winding fibers. Filament winding roving fibers shall be
in accordance with MIL-R-60346. Other fibers considered for use shall have a
minimum tensile strength of 150,000 psi and must be approved by the Naval Air
Systems Command.
3.14.1.2 Insulative fibers. Insulative fibers applied to the outside face
of the composite shall be capable of withstanding a temperature of 2,000F
for 20 minutes without disintegration or loss of more than 90 percent of its
original breaking strength.
3.14.2 Fabrics. Fabrics shall be chosen for the use intended and shall be
of the highest quality consistent with high strength-low weight construction.
Fabric sizing used to increase composite fabric to resin bond strength shall
be compatible with the composite resin system used.
3.14.2.1 Structural fabrics. Structural fabrics shall be in accordance
with MIL-C-9084. Other fabrics considered for use in structural composites
shall have a minimum laminate tensile strength of 20,000 psi and must be
approved by the Naval Air Systems Command.
3.14.2.2. Insulative fabrics. Insulative fabric applied to the tank shall
be secured to the tank structural composite shell with sufficient continuous
insulative fibers to ensure that the fabric will remain in place when
subjected to the fuel fire requirements (see 3.15.4). Insulative fabrics
shall be capable of withstanding a temperature of 2,000F for 20 minutes
without disintegration or loSS of more than 90 percent of its original
laminate breaking strength.
3.14.3 Resins. Structural and adhesive resins of the best quality,
consistent with the specification requirements, shall be used,
3.14.3.1 Resins shelf life. Accurate records of resin shelf life shall be
maintained. Resin or other similar products having shelf life requirements
shall be disposed of when unused beyond the "use before" or shelf life date.
3.14.3.2 Structural composite resins. Structural composite resin systems
shall be phenolic resin in accordance with MIL-R-9299 or epoxy resin in
accordance with MIL-R-21931. Designs which incorporate other resin systems
must be approved by the Naval Air Systems Command. Fire retardant additives
considered for use with an approved resin system shall not cause catalysis or
degrade the physical properties of the approved system more than 10 percent.
3.14.3.3 Adhesive resins. Adhesive resins for structural bonding of
similar or dissimilar items shall be in accordance with MMM-A-132 and listed
on its qualified products list. Design which incorporated other resin systems
must be approved by the Naval Air Systems Command.
3.14.4 Sandwich core. Core materials shall be of the best quality
consistent with high strength-low weight construction. The core materials
shall not be readily combustible nor should the structural portion of the core
decompose to a point that it no longer thermally protects the inside
structural windings when subjected to the fuel fire requirements (see 3.15.4).
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