MIL-DTL-44117B
3.6.1.1 Forming of shell before molding. Forming of the helmet shell shall be accomplished
using either pinwheel preforms or a combination of pinwheel preforms and rectangular panels. For
either method, metallic fastening devices, such as staples, are not permitted unless they are in the
trim area. Application of resin shall not be permitted in this operation. Spot welding or sewing
with thread shall be permitted provided that evidence of these methods is not visible on the outside
surface of the finished helmet.
3.6.1.1.1 Pinwheel preform construction. The pinwheel preforms shall be similar in
configuration to that shown on Drawing 8-2-661 but may vary in size. The pinwheels shall each
be one continuous, integral piece of fabric. To facilitate forming of the preform, the pinwheels
may be cut up to within 2 1/2 inches of the center point of the pinwheel, leaving an uncut area
measuring a minimum of 5 inches across in any direction. There shall be no more than eight legs,
of approximately equal dimensions, on each pinwheel. A maximum of one pinwheel, may be
formed by using two (2) half pinwheels joined together with a minimum 3 inch by 5 inch rectangle
of the same material used for the pinwheels. The 5 inch dimension shall be centered and parallel to
the butted joint of the two (2) half pinwheels. This segmented pinwheel layer may be located
anywhere within the preform layup other than the innermost or outermost preform layer. The
pinwheel preforms shall be assembled with four crown plies, similar to Drawing 8-2-661 so that
there are not less than 33 layers of fabric throughout any cross-sectional area of the shell. The
pinwheel preforms shall be superimposed over each other such that the gaps of each layer are
offset from the gaps of all other layers. Gaps in the pinwheel preforms shall not exceed 3/32 inch
in width. There shall be no pleat, wrinkle, or crease greater than 1/2 inch length. Any pleat,
wrinkle, or crease 1/2 inch or less in length shall be smooth.
3.6.1.1.2 Combination pinwheel preform and rectangular panel construction. The combination
pinwheel preform and rectangular panel construction shall consist of rectangular panels
sandwiched between a single outer and a single inner fabric layer of pinwheel construction. The
panels shall be rectangular in shape, cut in the warp and filling direction and the size may vary
providing that no dimension is less than 3 inches. In addition to rectangular panels, the crown may
contain circular or oval-shaped plies provided that the radius to any point on the periphery is not
less than 2 1/2 inches. The individual preform layers shall be superimposed over each other such
that the gaps of any two adjacent layers are offset by a minimum of 1/2 inch. The panels shall be
laid up so that there are not less than 33 layers of fabric, including the inner and outer pinwheel
layers, throughout any cross-sectional area of the shell. There shall be no pleat, wrinkle or crease
greater than 1/2 inch in length. Any pleat, wrinkle, or crease 1/2 inch or less in length shall be
smooth.
3.6.1.2 Molding of shell. The shell shall be formed during a single molding cycle, which is
defined as the time between the closing and opening of the mold one time only (breathing
degassing, or pinching off is not considered opening or closing the mold in this context). The shell
shall not be remolded after this single molding cycle. The outer and inner surfaces of the molded
shell shall be smooth. Both the inside and outside surfaces shall be free from any hole, void,
delamination, pimple, blister, cracking, crazing, dry spot, area of non-resin flow, or pit greater than
1/8 inch in diameter and greater than the depth of one ply. Permissible gaps and pits shall be filled
with epoxy resin composition to provide smooth and continuous surfaces on both surfaces of the
shell. There shall be no pleat, wrinkle, or crease on the inside or outside of the helmet shell, except
as allowed in 3.6.1.1.1 or 3.6.1.1.2. Any presence or evidence of delaminations and/or blistering
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