1. Combined Resin Infusion – Bladder Molding Technique for Manufacturing Composite Tubes
Presenters: Andrew Brady & Bert Mannhalter
Composites and Polymer Engineering Laboratory
South Dakota School of Mines & Technology
Rapid City, SD
12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018

2. 12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018
Contributors
Andrew Brady
Composites Engineer
Composites and Polymer Engineering (CAPE) Lab, South Dakota School of Mines & Technology
Bert Mannhalter
Research Engineer
David Salem
Director
John Goodwin
Project Engineer
Indian Head EOD Technology Division, Naval Surface Warfare Center
12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018

3. 12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018
Outline
Introduction
Goal
Approach
Experimental
Results
Conclusion
Next Step
Acknowledgements
12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018

4. 12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018
Introduction
The propellant grain for the Mk 122 Mod 1 Parachute Deployment Rocket Motor (PDRM) uses a thin-walled composite tube, known as a grain sleeve. The current grain sleeves are produced using a custom made braided nylon sleeving and epoxy resin.
12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018

5. 12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018
Goal
Produce PDRM Grain Sleeve
Requirements:
Meets dimensional specifications
Uses braided sleeving, sleeving must be off-the-shelf
Uses off-the-shelf liquid resin and liquid curing agent
Meets CTE requirements
Meets chemical compatibility requirements
Meets motor production temperature requirements
Meets service temperature requirements
Understand Effect of Moisture on Composite Tube Dimensions
Process Development
12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018

6. 12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018
Approach
Process Options
Traditional Bladder Molding
Vacuum Resin Infusion
Rigid Mandrel/High Pressure Resin
Combined Resin Infusion – Bladder Molding
12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018

7. 12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018
Approach
Traditional Bladder Molding
Utilizes a rigid outer mold to determine outside part finish and dimensions.
Utilizes a flexible bladder to determine the inside part finish and dimensions.
Excellent control of outer part dimensions and finish, flexibility of the bladder may result in wall thickness variations.
Bladder molding process is traditionally limited to prepreg materials.
Bladder is easily removable, typically disposable.
12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018

8. 12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018
Approach
Vacuum Resin Infusion
Utilizes mandrel inside of part and flexible bag/film as outer “mold”.
Excellent control of inner part dimensions and finish.
Poor control of outer part dimensions and finish.
Utilizes liquid resins.
Mandrel must be tapered, or significant forced used to remove (hydraulic/mechanical puller).
12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018

9. 12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018
Approach
Rigid Mandrel/High Pressure Resin (RTM, RIM)
Mold consists of a precision mandrel (inside of part) and outer mold.
Mandrel must interface outer mold for positioning and alignment.
Excellent dimensional control and surface finish on all part surfaces.
Resins of high-viscosities may be infused under high pressure.
Mandrel must be tapered, or significant forced used to remove (hydraulic/mechanical puller).
12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018

10. 12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018
Approach
Combined Resin Infusion – Bladder Molding
Utilizes a rigid outer mold to determine part dimensions and shape.
Utilizes a flexible bladder to determine the inside finish of the part.
Excellent control of outer part dimensions and finish, flexibility of the bladder may result in wall thickness variations.
Utilizes liquid resins.
Bladder is easily removable, typically disposable.
12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018

11. 12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018
Approach
Because the inner surface of the composite tubes will be further manipulated and coated with a elastomeric liner, the trade-off of inner surface control for reduced cost is acceptable.
12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018

12. 12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018
Experimental
Mold Design
Outer clamshell mold fully encapsulating part and bladder.
Ports accessing mold cavity to accommodate resin infusion.
Means to pressurize bladder after infusion.
12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018

13. 12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018
Experimental
Clamshell Mold
Static Plug
Braided Nylon Sleeve
Silicone Bladder
Positive Bladder Pressure Plug
12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018

14. 12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018
Experimental
Resin
Vacuum
Pressure
12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018

15. 12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018
Experimental
Left: infusion using 3,500cP resin. Right: infusion using 325cP resin.
Benchtop resin infusions were carried out using the nylon sleeving and resins of varying viscosity.
The benchtop infusions proceeded very slowly, suggesting that a very low viscosity resin would be necessary for successful tube production.
12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018

16. 12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018
Experimental
First infusion in the tube mold utilized typical infusion resin, and completed in significantly less time than expected.
Subsequent infusions have been completed with resins of viscosities as high as cP.
Because the infusion takes place within the metal mold where it is not visible, an explanation for the ability to infuse such high viscosity resins was not immediately obvious.
“Virtual Flow Media” theory
Due to the dimensions and the elasticity of the bladder, a small empty space exists between the reinforcement sleeve and the mold wall.
Resin flows into the empty space, travelling quickly along the length of the reinforcement sleeve.
Resin flows from the empty space, through the (relatively small) thickness of the reinforcement sleeve.
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17. 12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018
Results
Photo of CAPE grain sleeve.
Composite tubes of consistent dimensions and quality were produced using the proposed process.
Outer dimensions and geometric variations were within tolerance.
Wall thickness dimension and variation were found to be limited by those qualities of the reinforcement sleeve, with influence by processing parameters.
12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018

18. 12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018
Conclusion
A process suitable for producing composite tubes from off-the-shelf braided-sleeve reinforcement and high viscosity liquid resin was proposed and developed.
The developed process did not require several of the challenging components of solid mandrel/high pressure molding
Solid mandrel replaced with flexible bladder
High-pressure injection replaced with “Virtual Flow Media”
Mandrel puller not required due to flexibility and self-release quality of silicone bladder.
12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018

19. 12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018
Next Step
Produce PDRM Grain Sleeve
Requirements:
Meets dimensional specifications
Uses braided sleeving, sleeving must be off-the-shelf
Uses off-the-shelf liquid resin and liquid curing agent
Meets CTE requirements
Meets chemical compatibility requirements
Meets motor production temperature requirements
Meets service temperature requirements
Understand Effect of Moisture on Composite Tube Dimensions
Process Development
Complete
Product Development/Production
12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018

20. 12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018
Acknowledgements
DOTC INIT1199; Development of Additive Manufacturing Technologies for Energetic Materials Base Agreement No Lori Groven – Assistant Professor, South Dakota School of Mines & Technology Jan Puszynski – VP for Research, South Dakota School of Mines & Technology Magdy Bichay – CAD Technologist, Indian Head EOD Technology Division, Naval Surface Warfare Center
12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018