US 5,853,651 AGranted

High pressure hollow process for manufacturing composite structures

AssigneeSimula, Inc.

InventorsHoward A. Lindsay, Jeffrey A. Mears, Robert F. Monks, Steven M. Motoyama, Christopher K. DeLap

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Abstract

A method of fabricating complex hollow composite structures from laminates of fiber reinforced synthetic resins. The structures are fully monocoque tubes with no seams. The tubes are manufactured by wrapping a hollow semi-rigid inner mandrel made of thermoplastic material such as polystyrene or ABS (acrylonitrile-butadiene-styrene co-polymer) with layers of composite sheets. The sheets are made from high-strength fibers impregnated with thermosetting or thermoplastic resins. The laminated mandrel is placed in a mold, heated and inflated to a predetermined pressure. The pressure can range from 20-200 psig and even higher, while the curing temperature can range from 200.degree.-600.degree. F. The pressure generated by the expanding core produces a highly consolidated composite structure that has fewer voids, a more uniform thickness, and an increased fiber content compared to hollow composites made by other fabrication methods.

Claims21

Dependent claims

A method for manufacturing a hollow composite structure comprising:

(a) manufacturing a first half and a second half of a hollow semi-rigid inner mandrel from a thermoplastic material;
(b) placing an elastomeric tube inside the first half of the inner mandrel, and taping the second half of the inner mandrel over the elastomeric tube and the first half of the inner mandrel;
(c) wrapping the inner mandrel with layers of plies of a composite prepreg of thermosetting or thermoplastic resin having high strength reinforcement fibers therein, such that the layers of plies can be characterized as having an angle between successive layers, and such that said successive layers of said plies overlap with the angle between said successive layers of said plies have fiber orientations of at least three angles selected from the group consisting of -60.degree., -45.degree., -30.degree., 30.degree., 30.degree., 45.degree., 60.degree. and 90.degree.;
(d) placing the plies of said composite prepreg and the inner mandrel together in a mold for fabricating the hollow composite structure;
(e) inflating the elastomeric tube to a pressure in excess of 20 psi;
(f) heating the plies of said composite prepreg and the inner mandrel to an elevated temperature in excess of 200.degree. F.;
(g) selecting a time period of at least fifteen minutes and curing the plies of said composite prepreg and the inner mandrel at the elevated temperature for the selected time period;
(h) allowing the plies of said composite prepreg and the inner mandrel to cool to a temperature below 150.degree. F., at a maximum cooling rate of five to seven.degree. F. per minute;
(i) removing the elastomeric tube;
and
(j) removing the mandrel by solvent extraction thereby providing said hollow composite structure.

8 more elements

A method form fabricating hollow tubular structures comprising:

(a) fabricating two patterns;
(b) placing a separate sheet of thermoformable material over a corresponding one of said two patterns, each said separate sheet having at least one edge;
(c) taping each said separate sheet of thermoformable material at the at least one edge to the corresponding one of said two patterns and then placing each of said two patterns in separate vacuum bags;
(d) placing the vacuum bags in an oven;
(e) heating the oven to an elevated temperature until each said separate sheet of thermoformable material is forced into the corresponding one of said two patterns, such that each said separate sheet now forms one half of a mandrel;
(f) selecting a time period and holding each said one half of the mandrel under vacuum at the elevated temperature for the selected time period;
(g) allowing each said one-half of the mandrel to cool below 200.degree. F. and removing the two patterns from the oven;
(h) removing each said one half of the mandrel from the two patterns to provide a first half and a second half of the mandrel;
(i) trimming all of the thermoformable material that is in excess of the first half and the second half of the mandrel;
(j) placing an elastomeric bladder having a breather strip in the first half of the mandrel;
(k) placing the second half of the mandrel over the elastomeric bladder, and taping the first half and the second half of the mandrel together, thus forming a tubular mandrel, said tubular mandrel containing the elastomeric bladder;
(l) preparing tapes of a prepreg material comprising a resin and reinforcing fibers;
(m) wrapping the tapes of said prepreg material over the tubular mandrel using at least two relative orientations selected from the group of relative orientations consisting of 0.degree., .sup.+ 45.degree., .sup.+ 60.degree., and 90.degree.;
(n) placing the wrapped tubular mandrel in a curing mold;
(o) placing the curing mold in an oven;
(p) selecting a pressure between 20 psi and 200 psi, and inflating the elastomeric bladder to the selected pressure;
(q) selecting a temperature between 200.degree. F. and 600.degree. F., and raising the temperature of the oven to the selected temperature;
(r) curing the prepreg material to form a hollow tubular structure;
(s) removing the hollow tubular structure from the oven;
and
(t) removing the tubular mandrel from the hollow tubular structure by solvent extraction.

18 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/711,181Filed 28 Aug 1996
Granted: 29 Dec 1998
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

B29C 70/446
Using isostatic pressure, e.g. pressure difference-moulding, vacuum bag-moulding, autoclave-moulding or expanding rubber-moulding: moulding…
B29L 2031/603
Composed of several elementary tubular elements: one placed inside the other, e.g. dual wall tubes
B62K 19/16
Characterised by material or cross-section of frame members: the material being wholly or mainly of plastics
Y10S 264/44
Plastic and nonmetallic article shaping or treating: processes: using destructible molds or cores in molding processes