Blade Stringer Assemblies with Fabric and Tape Composite Stiffeners
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Solution Overview
Problem
The manufacturing of all-tape blade stringers is challenging due to complex build-up procedures and the need for numerous parts, particularly when forming around sharp bends, as conventional methods involve complex build-up procedures and the use of gap fillers which introduce voids and manufacturing complexities.
Innovation Solution
A stringer assembly comprising a first fabric composite stiffener, a second fabric composite stiffener, and an intermediate tape composite stiffener, where the intermediate tape stiffener is bonded to both fabric stiffeners, allowing for sharper bends and eliminating the need for gap fillers by using three separate components with specific geometries and orientations to enhance rigidity and prevent delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional methods are used to form tape plies into blade stringers, then the stringers can be manufactured, but the build-up procedures become complex and require numerous parts including gap fillers
Solution Approach 1:
The stringer is divided into three distinct components: first fabric composite stiffener, second fabric composite stiffener, and intermediate tape composite stiffener. This segmentation allows each component to be manufactured and formed independently, simplifying the overall build-up procedure while reducing the need for additional parts like gap fillers.
Solution Approach 2:
The intermediate tape composite stiffener is bonded to both fabric stiffeners, merging the tape and fabric construction into a unified assembly. This combining approach eliminates the need for separate gap fillers and reduces the total number of parts required while maintaining structural integrity.
2Ease of manufacture
If composite tapes are used, then surface treatment requirements are reduced, but the tapes are harder to form on contours and corners compared to composite fabrics
Solution Approach 1:
Different regions of the stringer use different materials optimized for their specific functions: fabric composite stiffeners are used in regions requiring contour conformability (web and flange portions), while tape composite stiffener is used in the intermediate region where high axial stiffness is needed. This local quality differentiation allows each material to perform optimally.
Solution Approach 2:
The stringer employs a hybrid composite structure combining both fabric and tape composite materials. This composite approach leverages the advantages of both materials: fabric provides drapability and contour conformity, while tape provides high axial stiffness and reduced surface treatment requirements.
3Ease of operation
If fabric composite stiffeners are used, then the materials are easier to form on contours, but the axial stiffness is lower compared to tape composites
Solution Approach 1:
The stringer design applies fabric composite material specifically in the web and flange portions where contour conformity and drapability are critical, while applying tape composite material in the intermediate portion where high axial stiffness is required. This localized material selection optimizes both properties in their respective locations.
Solution Approach 2:
By combining fabric and tape composite materials in a single stringer assembly, the design achieves both high drapability (from fabric) and high axial stiffness (from tape), resolving the trade-off between these two properties through material heterogeneity.
4Shape
If the stringer uses sharp bends, then the geometry is optimized, but voids and gap fillers are introduced in conventional methods
Solution Approach 1:
By segmenting the stringer into three independently formable components, the design enables sharp bends at the interfaces between components without introducing voids. The intermediate tape stiffener acts as a form tool that shapes the fabric stiffeners into sharp contours while maintaining structural integrity through bonding.
Solution Approach 2:
The intermediate tape composite stiffener serves as a mediator between the two fabric stiffeners, providing a stable form tool that enables sharp bend geometry while eliminating the need for gap fillers. The bonding between components ensures structural integrity is maintained despite the sharp geometric transitions.
Data Source
AI summary
Described herein are stringer assemblies, such as blade stringers, and methods of forming thereof. A stringer assembly comprises a first fabric composite stiffener, a second fabric composite stiffener, and an intermediate tape composite stiffener, disposed between and connected to each of the first and second stiffeners. Using three separate components allows forming sharp bends, eliminating voids and gap fillers, and adding new features, such as edge reinforcements. Each of the first and second fabric composite stiffeners comprises a web portion, a flange portion, and a curved portion, positioned between the web and flange portions. The web portions surround and are attached to the intermediate tape composite stiffener and, in some examples, include tapered-out edges for additional rigidity. The flange portions are attached to the composite base. The curved portions conform to the flared-out edges of the intermediate tape composite stiffener, which extends and connects to the composite base.