Method of making polyimide foam structures of controlled density and increased rigidity
First Claim
1. The method of making a composite structure having a uniform polyimide foam component of controlled density, which comprises the steps of:
- providing a substantially open-cell polyimide foam core having substantially uniform cell size and subtantially uniform density;
impregnating said foam core with a liquid polyimide precursor;
compressing said foam shape to squeeze out all but a desired quantity of liquid precursor;
bringing said face sheet into contact with said foam core;
heating the resulting assembly to a temperature sufficient to cure said polyimide precursor; and
whereby a strong, well bonded asesmbly having a uniform selected core density results.
2 Assignments
0 Petitions
Accused Products
Abstract
A method of making structural panels having a controlled density polyimide core, generally with at least one face sheet. An open cell polyimide foam panel is impregnated with a liquid polyimide precursor, compressed to squeeze out all but a desired quantity of the polyimide precursor and dried. One or two face sheets are impregnated with the same liquid polyimide precursor and placed on one or both faces of the foam panel, with pre-drying of the face sheet if desired. This assembly is placed in a mold and subjected to slight compression. The assembly is heated to a moderate temperature for a suitable time to take on the mold configuration. Then the assembly is heated to the curing temperature of the polyimide precursor for a period sufficient to cause curing. The resulting structural panel has a selected density, which determines strength and rigidity, weight and other physical characteristics, controlled by the amount of precursor allowed to remain after the impregnation foam compression step.
85 Citations
16 Claims
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1. The method of making a composite structure having a uniform polyimide foam component of controlled density, which comprises the steps of:
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providing a substantially open-cell polyimide foam core having substantially uniform cell size and subtantially uniform density; impregnating said foam core with a liquid polyimide precursor; compressing said foam shape to squeeze out all but a desired quantity of liquid precursor; bringing said face sheet into contact with said foam core; heating the resulting assembly to a temperature sufficient to cure said polyimide precursor; and whereby a strong, well bonded asesmbly having a uniform selected core density results. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. The method of making structural panels having a polyimide foam core bonded between face sheets which comprises the steps of:
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providing a substantially open-cell polyimide foam core; impregnating said foam core with a liquid polyimide precursor; compressing said foam core to squeeze out all but the desired quantity of said polyimide precursor; drying said foam core at a temperature below the cure temperature of said polyimide precursor; impregnating two face sheets with said polyimide precursor; drying said two face sheets at a temperature below the cure temperature of said polyimide precursor; placing said face sheets on opposite sides of said foam core; placing the resulting assembly between mold surfaces adjusted to slightly compress said foam assembly; heating said assembly at a temperature below the curing temperature of said polyimide precursor for a period sufficient to allow said assembly to take the shape of the mold surfaces; heating said assembly at a temperature sufficient to cure said polyimide precursor for a time period sufficient to produce complete cure; and removing the resulting bonded composite structural panel from the mold. - View Dependent Claims (14, 15, 16)
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Specification