Equipment for making composite tubes including an inflatable heated bladder and a composite mold having a negative coefficient of thermal expansion

• US 5,071,506 A
• Filed: 01/25/1990
• Issued: 12/10/1991
• Est. Priority Date: 10/09/1987
• Status: Expired due to Fees

• Current Assignee: Alliant Techsystems Incorporated (Northrop Grumman Corporation)
• Original Assignee: Thiokol Corporation (Howmet Aerospace, Inc.)
• Inventors: Nelson, David R., Youngkeit, Dean C.
• Primary Examiner(s): Ball, Michael W.
• Assistant Examiner(s): Aftergut, Jeff H.
• Application Number:
  US07/471,002
• Time in Patent Office: 684 Days
• Field of Search: 156/194, 156/173, 156/425, 156/156, 156/175, 156/169, 156/242, 156/433, 156/245, 156/441, 156/428-430, 156/285, 156/286, 249/134, 249/82, 249/152, 264/523, 264/572, 264/573, 264/574, 425/387.1
• US Class Current: 156/441
• CPC Class Codes: B29C 33/3828 Moulds made of at least two different materials having different thermal conductivities
• CPC Class Codes: B29C 33/40 Plastics, e.g. foam or rubber
• CPC Class Codes: B29C 43/12 using bags surrounding the moulding material or using membranes contacting the moulding material
• CPC Class Codes: B29C 70/446 Moulding structures having an axis of symmetry or at least one channel, e.g. tubular structures, frames
• CPC Class Codes: B29D 23/001 Pipes; Pipe joints pleated hoses B29D23/18

Abstract

A process and equipment for making seamless composite tubes. Composite material is applied on a mandrel which includes an inflatable bladder and inserted in a single piece mold. The bladder is pressurized for pressing the composite material against the mold wall for molding and curing thereof. In order to prevent seizing of the tube by the mold and thus allow easy removal of the cured tube, the mold is composed of a composite of resin impregnated carbon fiber material wherein the carbon fiber material has a negative coefficient of thermal expansion along the length thereof and is oriented at an angle of between about 15 and 40 degrees relative to a radial plane of the mold. In order to eliminate the use of inefficient and inconvenient cure ovens, a heat generating element is disposed internally of the mandrel for curing of the composite material.

Claims

1. Apparatus for making a seamless composite tube comprises a mold which includes an elongate single piece carbon fiber and resin composite and aperture means extending longitudinally through said composite for insertion of a mandrel on which resin impregnated fibrous material may be applied for curing and molding thereof, a mandrel which includes an elongate cylindrical body having a pair of end portions and cavity means internally thereof and intermediate said end portions and insertable in said aperture means for curing and molding of resin impregnated fibrous material applied thereon, means comprising an electrical heating element disposed in said cavity means and electrical wires for supplying electrical energy to said heating element for generating heat for curing resin impregnated fibrous material applied on the mandrel, a radially outer surface on said body, bladder means disposed about said radially outer surface and responsive to pressurizing thereof for pressing a resin impregnated fibrous material which is applied thereon outwardly against said aperture means for molding of the resin impregnated fibrous material, passage means in each of said end portions for applying air pressure for pressurizing said bladder means, air pressure inlet means in one of said mandrel end portions, said passage means being in flow communication with said cavity means whereby said cavity means allows the passage of air pressure between said passage means in both said end portions, means in the other of said mandrel end portions for routing said electrical wires into said cavity means for connection to said heating element, and means for sealing said routing means against escape of air pressure from said cavity means, said single piece composite including carbon fibrous material which has a negative coefficient of thermal expansion and the fibers thereof are oriented at an angle which is between about 15 and 40 degrees relative to a radial plane of the mold.

2. Apparatus according to claim 1 further comprises rigid means including a cylindrical member disposed about said single piece composite in closely surrounding relation for maintaining straightness of the single piece composite.

3. Apparatus according to claim 2 wherein said cylindrical member is composed of a composite of cured resin impregnated carbon fibrous material wherein the fibers thereof are oriented at an angle which is greater than about 60 degrees relative to a radial plane of the mold.

4. Apparatus according to claim 3 wherein the fibers of said carbon fibrous material of said single piece composite are oriented at an angle which is between about 25 and 35 degrees relative to a radial plane of the mold.

5. Apparatus according to claim 1 wherein the fibers of said carbon fibrous material of said single piece composite are oriented at an angle which is between about 25 and 35 degrees relative to a radial plane of the mold.

6. Apparatus according to claim 1 wherein the fibers of said carbon fibrous material of said single piece composite are oriented at an angle of about 30 degrees relative to a radial plane of the mold.

7. Apparatus according to claim 1 wherein said bladder means is composed of silicone rubber.

8. Apparatus for making a seamless composite tube comprises a mold which includes an elongate single piece carbon fiber and resin composite and aperture means extending longitudinally through said composite for insertion of a mandrel on which resin impregnated fibrous material may be applied for curing and molding thereof, a mandrel which includes an elongate cylindrical body having a pair of end portions and cavity means internally thereof and intermediate said end portions and insertable in said aperture means for curing and molding of resin impregnated fibrous material applied thereon, means comprising an electrical heating element disposed in said cavity means and electrical wires for supplying electrical energy to said heating element for generating heat for curing resin impregnated fibrous material applied on the mandrel, a radially outer surface on said body, bladder means disposed about said radially outer surface and responsive to pressurizing thereof for pressing a resin impregnated fibrous material which is applied thereon outwardly against said aperture means for molding of the resin impregnated fibrous material, passage means in each of said end portions for applying air pressure for pressurizing said bladder means, air pressure inlet means in one of said mandrel end portions, said passage means being in flow communication with said cavity means whereby said cavity means allows the passage of air pressure between said passage means in both said end portions, means in the other of said mandrel end portions for routing said electrical wires into said cavity means for connection to said heating element, means for sealing said routing means against escape of air pressure from said cavity means, and rigid means including a cylindrical member disposed about said single piece composite in closely surrounding relation for maintaining straightness of the single piece composite.

9. Apparatus according to claim 8 wherein said bladder means is composed of silicone rubber.

10. Apparatus for making a seamless composite tube comprises a mold which includes an elongate single piece carbon fiber and resin composite and aperture means extending longitudinally through said composite for insertion of a mandrel on which resin impregnated fibrous material may be applied for curing and molding thereof, a mandrel which includes an elongate cylindrical body having a pair of end portions and cavity means internally thereof and intermediate said end portions and insertable in said aperture means for curing and molding of resin impregnated fibrous material applied thereon, means comprising an electrical heating element disposed in said cavity means and electrical wires for supplying electrical energy to said heating element for generating heat for curing resin impregnated fibrous material applied on the mandrel, a radially outer surface on said body, bladder means disposed about said radially outer surface and responsive to pressurizing thereof for pressing a resin impregnated fibrous material which is applied thereon outwardly against said aperture means for molding of the resin impregnated fibrous material, passage means in each of said end portions for applying air pressure for pressurizing said bladder means, air pressure inlet means in one of said mandrel end portions, said passage means being in flow communication with said cavity means whereby said cavity means allows the passage of air pressure between said passage means in both said end portions, means in the other of said mandrel end portions for routing said electrical wires into said cavity means for connection to said heating element, means for sealing said routing means against escape of air pressure from said cavity means, and rigid means including a cylindrical member disposed about said single piece composite in closely surrounding relation for maintaining straightness of the single piece composite, said cylindrical member is composed of a composite of cured resin impregnated carbon fibrous material wherein the fibers thereof are oriented at an angle which is greater than about 60 degrees relative to a radial plane of the mold.

11. Apparatus according to claim 10 wherein said bladder means is composed of silicone rubber.

12. A mandrel for making a composite tube comprises an elongate cylindrical body having a pair of end portions and a cavity means internally thereof and intermediate said end portions and further having a radially outer surface, bladder means disposed about said radially outer surface and responsive to pressurizing thereof for pressing a resin impregnated fibrous material which is applied thereon outwardly against an inner wall of a female mold in which the mandrel and applied resin impregnated fibrous material is inserted for molding thereof, means comprising an electrical heating element disposed in said cylindrical body cavity means and electrical wires for supplying electrical energy to said heating element for generating heat for curing resin impregnated fibrous material applied on the mandrel, passage means in each of said end portions for applying air pressure for pressurizing said bladder means, air pressure inlet means in one of said mandrel end portions, said passage means being in flow communication with said cavity means whereby said cavity means allows the passage of air pressure between said passage means in both said end portions, means in the other of said mandrel end portions for routing said electrical wires into said cavity means for connection to said heating element, and means for sealing said routing means against escape of air pressure from said cavity means.

13. A mandrel according to claim 12 wherein said bladder means is composed of silicone rubber.

14. Apparatus for making a seamless composite tube comprises a mold which includes an elongate single piece carbon fiber and resin composite and aperture means extending longitudinally through said composite for insertion of a mandrel on which resin impregnated fibrous material may be applied for curing and molding thereof, a mandrel which includes an elongate cylindrical body having a pair of end portions and cavity means internally thereof and intermediate said end portions and insertable in said aperture means for curing and molding of resin impregnated fibrous material applied thereon, means comprising an electrical heating element disposed in said cavity means and electrical wires for supplying electrical energy to said heating element for generating heat for curing resin impregnated fibrous material applied on the mandrel, a radially outer surface on said body, bladder means disposed about said radially outer surface and responsive to pressurizing thereof for pressing a resin impregnated fibrous material which is applied thereon outwardly against said aperture means for molding of the resin impregnated fibrous material, passage means in each of said end portions for applying air pressure for pressurizing said bladder means, air pressure inlet means in one of said mandrel end portions, said passage means being in flow communication with said cavity means whereby said cavity means allows the passage of air pressure between said passage means in both said end portions, means in the other of said mandrel end portions for routing said electrical wires into said cavity means for connection to said heating element, and means for sealing said routing means against escape of air pressure from said cavity means.

15. Apparatus according to claim 14 wherein said bladder means is composed of silicone rubber.