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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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 7800 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. 12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018

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

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

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

12th CAD/PAD Technical Exchange Workshop May 15th-17th, 2018 Acknowledgements DOTC-16-01 INIT1199; Development of Additive Manufacturing Technologies for Energetic Materials Base Agreement No. 2017-328 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