Developing Extractable Tooling to Adapt Bladder Molding of Short Fiber Composites to Create Bent Formations

• Logan Blackburn, Computer Engineering, University of Delaware

• Tom Cender, Center for Composite Materials, University of Delaware

With traditional, continuous carbon fiber composites, the ability of forming the material to create complex geometries is highly limited. However, with TuFF (Tailored Universal Feedstock for Forming), a short fiber composite, complex parts can be stretch formed using a bladder molding process. Previous work has demonstrated a hollow, corrugated cylindrical strut can be formed with this process. In this method, unidirectional plies of TuFF were laminated onto an inner cylindrical tool and inflated to and outer mold surface in order to avoid the development of wrinkles in the composite. After molding, the straight tool is pulled from the expanded composite part for removal. While this process is sufficient for straight parts, challenges arise in removing the inner tool if the part is a bent shape. In order to generate highly tailored composite designs, this project aims to adapt the tooling to develop an extractable tool that increases design freedom. The new tool concept was developed to be disassembled from within the completed part and allow for removal. The tool utilizes a multi-piece stainless steel rod that is screwed together for assembly as well as Aquacore washable ceramic material to create a rigid core that can be washed away after the part is formed. A straight prototype tool was fabricated and successfully tested using the new design where disassembly after forming can be done without removing the tool from the part. With this design, future tests will be done to ensure the concept translates to forming bent geometries and allow for more complex composite parts to be formed.