Rigidification of structures to be deployed by inflating, particularly for use in space
The invention relates to the stiffening of inflatably deployable structures, in particular for space use. More specifically, the invention relates to a flexible membrane for inflatably deployable structures, that comprises one layer of a composite and at least one polymer film that is permeable to visible radiation covering one of the faces of this layer, said composite being formed from a fibrous material impregnated with a composition incorporating an epoxide or epoxy/acrylate resin and a photoinitiator, and which is characterized in that the photoinitiator is an iron-arene complex salt of general formula (I): where A is an arene group, while X is a non-nucleophilic anion. Applications: manufacture of devices of the following types: radars, solar panels, reflectors, solar shields, antennas, solar mirrors or sails, intended to equip orbital vehicles or vehicles for space or planetary exploration.
1. A structure which is inflatably deployable and stiffenable after being deployed, which comprises a flexible membrane, said membrane comprising at least one layer of a composite, said layer having a first face and a second opposite face, and at least one polymer film that is permeable to visible radiation and that covers the first face of the composite layer, said composite being formed from a fibrous material impregnated with a composition including a non-polymerized epoxide or epoxy/acrylate resin and a photoinitiator for initiating the polymerization of the resin upon irradiation of the membrane with a visible radiation and thereby obtaining the stiffening of the structure, wherein the photoinitiator is an iron-arene complex salt of formula (I):
in which A represents an arene group while X represents a non-nucleophilic anion.
2. The structure according to claim 1 , wherein the photoinitiator is an iron-arene complex salt of formula (I) in which the arene group is an aromatic monocyclic or polycyclic group comprising from 6 to 32 carbon atomsin the aromatic ring optionally substituted by one or more groups; independently selected from the group consisting of a halogen atom, a linear alkyl, a branched alkyl, an alkoxyl group, a haloalkyl group, a nitroalkyl group, a cyanoalkyl group and an alkoxycarbonyl group.
3. The structure according to claim 2 , wherein the photoinitiator is an iron-arene complex salt of formula (I) wherein the arene group is selected from the group consisting of benzene, cumene, naphthalene, methylnaphthalene, phenanthrene, fluorene, coronene and ovalene.
4. The structure according to claim 1 , wherein the photoinitiator is an iron-arene complex salt of formula (I) wherein the non-nucleophilic anion is a halogen or chlorine anion of an element selected from the group consisting of boron, phosphorus, arsenic, antimony, iron and bismuth, or an anion of fluoroaliphatic or perfluoroaromatic sulphonic acid.
5. The structure according to claim 1 , wherein the photoinitiator is cyclopentadienyl(1-methylnaphthalene)iron hexafluorophosphate.
6. The structure according to claim 1 , wherein the photoinitiator represents from 0.1% to 10% by weight of the weight of the resin.
7. The structure according to claim 6 , wherein the photoinitiator represents from 0.2 to 5% by weight of the weight of the resin.
8. The structure according to claim 1 , wherein the fibrous material is a material formed from carbon fibres, glass fibres or a mixture of these fibres.
9. The structure according to claim 1 , wherein the resin is a bisphenol A diglycidyl ether (BADGE) or a multifunctional acrylic derivative of such a resin.
10. The structure according to claim 1 , wherein said membrane has an inner face and an outer opposite face and wherein the polymer film that is permeable to visible radiation forms the inner face of the membrane, while the second face of the composite layer is covered with a thermal cover that forms the outer face of the membrane.
11. The structure according to claim 1 , wherein the composite layer is inserted between a first polymer film and a second polymer film that are permeable to visible radiation, and that are identical or different.
12. The structure according to claim 11 , wherein said membrane has an inner face and an outer opposite face and wherein the first polymer film forms the inner face of the membrane, while the second polymer film is covered with a thermal cover which forms the outer face of the membrane.
13. The structure according to claim 1 , wherein the polymer film that is permeable to visible radiation is an aromatic polyimide film, a polyarylene ether benzimidazole film or a polybenzoxazole film.
14. The structure according to claim 13 , wherein the polymer film that is permeable to visible radiation is an aromatic polyimide film.
15. A method for stiffening a structure as defined in claim 1 , comprising:
a) irradiating the structure with visible radiation through said at least one polymer film that is permeable to visible radiation in order to initiate the polymerization of the resin present in this structure; and
b) heating the structure to activate the polymerization of said resin, wherein the heating of the structure may be carried out at the same time as or after its irradiation.
16. The method according to claim 15 , wherein the heating of the membrane is carried out after its irradiation.
17. The structure according to claim 2 , wherein said arene group is an aromatic monocyclic or polycyclic group comprising from 6 to 12 carbon atoms in the aromatic ring and is optionally substituted.