Ballistic helmets and method of manufacture thereof

A method of manufacturing a ballistic helmet comprising:

• a. hydroforming a helmet preform from a stack of 0/90 fabric layers impregnated with at least one resin according to a process comprising:
• 1) heating the stack of 0/90 fabric layers impregnated with the at least one resin at between 150° F. to 200° F. for about 20 to 45 minutes;
• 2) placing the heated stack of impregnated 0/90 fabric layers on a hydroforming blank holding ring on a hydroforming press;
• 3) closing the hydroforming press to bring a flexible rubber diaphragm against a top of the heated stack of impregnated 0/90 fabric layers;
• 4) pressurizing a forming chamber behind the flexible rubber diaphragm with a hydraulic oil to about 800-1500 psi;
• 5) raising a punch having a predefined shape and dimensions of an inside of a helmet preform from a bottom portion of the hydroforming press against a bottom of the heated stack of impregnated 0/90 fabric layers and up against the flexible rubber diaphragm and into the forming chamber;
• 6) holding the punch in the raised position for 10 to 15 seconds to form the preform with no overlaps, no seams, no cuts and a controlled orientation of the fibers;
• 7) lowering the punch back into the bottom portion of the hydroforming press;
• 8) opening the hydroforming press;
• and
• 9) removing the helmet preform;
• b. placing the helmet preform on a lower die of a matched metal die compression molding press that has been heated to between about 250° F. to 350° F.;
• c. closing the matched metal die compression molding press by bringing an upper die portion down on to the lower die portion of the matched metal die compression molding press;
• d. applying between about 500 psi and 5000 psi to the helmet preform for between about 15 to 25 minutes at between about 250° F. to 350° F. to form a molded helmet;
• e. cooling the matched metal die compression molding press and the molded helmet down to between about 100° F. to 180° F. over about 20 minutes at between about 500 psi and 3,000 psi;
• and
• f. removing the molded helmet from the matched metal die compression molding press.

A method of manufacturing a ballistic helmet comprising:

• a. hydroforming a helmet preform from a stack of 0/90 fabric layers impregnated with at least one resin according to a process comprising:
• 1) heating the stack of 0/90 fabric layers impregnated with the at least one resin at between 150° F. to 200° F. for about 20 to 45 minutes;
• 2) placing the heated stack of impregnated 0/90 fabric layers on a hydroforming blank holding ring on a hydroforming press;
• 3) closing the hydroforming press to bring a flexible rubber diaphragm against a top of the heated stack of impregnated 0/90 fabric layers;
• 4) pressurizing a forming chamber behind the flexible rubber diaphragm with a hydraulic oil to about 800-1500 psi;
• 5) raising a punch having a predefined shape and dimensions of an inside of a helmet preform from a bottom portion of the hydroforming press against a bottom of the heated stack of impregnated 0/90 fabric layers and up against the flexible rubber diaphragm and into the forming chamber;
• 6) holding the punch in the raised position for 10 to 15 seconds to form the preform with no overlaps, no seams, no cuts and a controlled orientation of the fibers;
• 7) lowering the punch back into the bottom portion of the hydroforming press;
• 8) opening the hydroforming press;
• and
• 9) removing the helmet preform;
• b. placing the helmet preform on a lower die of a matched metal die compression molding press that has been heated to between about 250° F. to 350° F.;
• c. closing the matched metal die compression molding press by bringing an upper die portion down on to the lower die portion of the matched metal die compression molding press;
• d. applying between about 500 psi to 5000 psi to the helmet preform for between about 15 to 25 minutes at between about 250° F. to 350° F. to form a molded helmet;
• e. removing the molded helmet from the matched metal die compression molding press;
• f. placing the molded helmet on a helmet-shaped punch in a hydroforming press;
• g. closing the hydroforming press to bring a flexible rubber diaphragm down against a top of the molded helmet;
• h. continuously and uniformly applying about 6000 psi to 10,000 psi of pressure while cooling the molded helmet down to between about 100° F. to 180° F. over about 2 minutes in the hydroforming press;
• and
• i. removing the molded helmet from the hydroforming press.

A method of manufacturing a ballistic helmet comprising:

• a. hydroforming a helmet preform from a stack of 0/90 fabric layers impregnated with at least one resin according to a process comprising:
• 1) heating the stack of 0/90 fabric layers impregnated with the at least one resin at between 150° F. to 200° F. for about 20 to 45 minutes;
• 2) placing the heated stack of impregnated 0/90 fabric layers on a hydroforming blank holding ring on a hydroforming press;
• 3) closing the hydroforming press to bring a flexible rubber diaphragm against a top of the heated stack of impregnated 0/90 fabric layers;
• 4) pressurizing a forming chamber behind the flexible rubber diaphragm with a hydraulic oil to about 800-1500 psi;
• 5) raising a punch having a predefined shape and dimensions of an inside of a helmet preform from a bottom portion of the hydroforming press against a bottom of the heated stack of impregnated 0/90 fabric layers and up against the flexible rubber diaphragm and into the forming chamber;
• 6) holding the punch in the raised position for 10 to 15 seconds to form the preform with no overlaps, no seams, no cuts and a controlled orientation of the fibers;
• 7) lowering the punch back into the bottom portion of the hydroforming press;
• 8) opening the hydroforming press;
• and
• 9) removing the helmet preform;
• b. heating the helmet preform to between about 240° F. to 250° F.;
• c. placing the heated helmet preform on a lower die of a matched metal die compression molding press that has been heated to between about 260° F. to 270° F.;
• d. closing the matched metal die compression molding press by bringing an upper die portion down on to the lower die portion of the matched metal die compression molding press;
• e. applying between about 1,500 psi to 3,000 psi pressure to the helmet preform for between about 18 to 20 minutes at between about 260° F. to 270° F. in the matched metal die compression molding press to form a molded helmet;
• f. cooling the matched metal die compression molding press and the molded helmet to between about 140° F. to 160° F. while maintaining between about 1,500 psi to 3,000 psi pressure to the helmet preform;
• g. removing the molded helmet from the matched metal die compression molding press;
• h. heating the molded helmet at about 260° F. to 270° F. for 30 to 45 minutes;
• j. placing the heated molded helmet on a helmet-shaped punch in a hydroforming press;
• k. closing the hydroforming press to bring a flexible rubber diaphragm down against a top of the heated molded helmet;
• l. continuously and uniformly applying about 6000 psi to 10,000 psi of pressure while cooling the molded helmet down to between about 100° F. to 180° F. over about 2 minutes in the hydroforming press;
• and
• m. removing the molded helmet from the hydroforming press.