Method for making a fiber reinforced crosslinked polyimide matrix composite article

Claim 1

A method for making a reinforced crosslinked polyimide resin matrix composite article, comprising: heating a plurality of plies of prepreg, said plies of prepreg each comprising reinforcing fibers and a reaction mixture, said reaction mixture initially comprising an aromatic diamine, an end cap monomer and at least one of an aromatic dianhydride, a diester-diacid of an aromatic dianhydride or a tetracid of an aromatic dianhydride, to a temperature between 245° and 265° C. and holding at said temperature for a period of time between 30 and 70 minutes so that the reaction mixture forms a low viscosity substantially noncrosslinked molten imide intermediate, wherein said heating step includes subjecting the heated plies of prepreg to subatmospheric pressure between 500 and 600 mm Hg to remove volatile impurities and volatile reaction-products from the plies of prepreg and form plies of imidized prepreg, stacking plies of imidized prepreg under superatmospheric pressure to a temperature and for a period of time sufficient to form the fiber reinforced crosslinked polyimide matrix composite article by consolidating he plies and crosslinking the imide intermediate, wherein the article so formed is substantially free of internal voids and surface blisters.

Claim 2

A method for making a reinforced crosslinked polyimide resin matrix composite article, comprising: heating a plurality of plies of prepreg, said plies of prepreg each comprising reinforcing fibers and a reaction mixture, said reaction mixture initially comprising an aromatic diamine, an end cap monomer and at least one of an aromatic dianhydride, a diester-diacid of an aromatic dianhydride or a tetracid of an aromatic dianhydride, to a temperature between 245° and 265° C. and holding at said temperature for a period of time between 30 and 70 minutes so that the reaction mixture forms a low viscosity substantially noncrosslinked molten imide intermediate, wherein said heating step includes subjecting the heated plies of prepreg to subatmospheric pressure between 500 and 600 mm Hg to remove volatile impurities and volatile reaction-products from the plies of prepreg and form plies of imidized prepreg, stacking plies of imidized prepreg under superatmospheric pressure to a temperature and for a period of time sufficient to form the fiber reinforced crosslinked polyimide matrix composite article by consolidating he plies and crosslinking the imide intermediate, wherein the article so formed is substantially free of internal voids and surface blisters.

Claim 7

A method for making a reinforced crosslinked polyimide resin matrix composite article, comprising: stacking a plurality of plies of prepreg, said plies of prepreg each comprising reinforcing fibers and a reaction mixture, said reaction mixture initially comprising an aromatic diamine, an end cap monomer and at least one of an aromatic dianhydride, a diester-diacid of an aromatic dianhydride or a tetracid of an aromatic dianhydride, to form a laminated prepreg, heating the laminated prepreg to a temperature between 245° and 265° C. and holding at said temperature for a period of time between 30 and 70 minutes so that the reaction mixture forms a low viscosity substantially noncrosslinked molten imidized intermediate, wherein said heating step includes subjecting the laminated prepreg to subatmospheric pressure between 500 and 600 mm Hg to remove volatile impurities and volatile reaction products from the laminated prepreg and form a laminated imidized prepreg, and heating the laminated imidized prepreg under superatmospheric pressure to a temperature and for a period of time sufficient to form the fiber reinforced crosslinked polyimide matrix composite article by consolidating the plies and crosslinking the imide intermediate, wherein he article so formed is substantially free of internal voids and surface blisters.

Claim 8

A method for making a reinforced crosslinked polyimide resin matrix composite article, comprising: stacking a plurality of plies of prepreg, said plies of prepreg each comprising reinforcing fibers and a reaction mixture, said reaction mixture initially comprising an aromatic diamine, an end cap monomer and at least one of an aromatic dianhydride, a diester-diacid of an aromatic dianhydride or a tetracid of an aromatic dianhydride, to form a laminated prepreg, heating the laminated prepreg to a temperature between 245° and 265° C. and holding at said temperature for a period of time between 30 and 70 minutes so that the reaction mixture forms a low viscosity substantially noncrosslinked molten imidized intermediate, wherein said heating step includes subjecting the laminated prepreg to subatmospheric pressure between 500 and 600 mm Hg to remove volatile impurities and volatile reaction products from the laminated prepreg and form a laminated imidized prepreg, and heating the laminated imidized prepreg under superatmospheric pressure to a temperature and for a period of time sufficient to form the fiber reinforced crosslinked polyimide matrix composite article by consolidating the plies and crosslinking the imide intermediate, wherein he article so formed is substantially free of internal voids and surface blisters.