Composite Strip Filler Edge Geometry to Prevent Ply Gaps
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Solution Overview
Problem
Composite structures, such as drive shafts, face challenges with damage initiation in areas of non-uniform thickness due to gaps between adjacent plies, which can lead to stress concentrations and reduced damage tolerance.
Innovation Solution
The use of composite strips with filler edges having specific geometries, such as chamfers, double bevels, and curved shapes, to prevent or reduce gaps between adjacent strips, thereby enhancing the structural integrity and damage tolerance of composite structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional composite structures use straight edges between adjacent plies, then manufacturing is simple, but gaps form between strips leading to stress concentrations and reduced damage tolerance
Solution Approach 1:
The patent applies local quality by modifying only the edge geometry of composite strips at specific locations where gaps occur, rather than changing the entire structure. The filler edges with chamfer, bevel, or curved geometries are applied locally at the interfaces between adjacent plies to prevent gap formation, while the rest of the composite structure maintains its conventional design.
Solution Approach 2:
The patent employs curvature by using curved filler edge geometries instead of straight edges. The curved profiles (convex or concave) allow the filler edges to better conform to the natural curvature of composite layups, particularly in rounded corners and transition zones, preventing gap formation that would occur with straight edges while maintaining manufacturing feasibility.
2Strength
If tapered shapes are created in zones of joints or rub-rings to add extra thickness, then stress concentrations are compensated, but gaps between adjacent plies are more likely to form
Solution Approach 1:
In tapered zones such as joints and rub-rings, the patent applies filler edges with specific geometries at each interface between adjacent plies. This local modification ensures that even in regions where thickness changes create natural gaps, the filler edges prevent gap formation and maintain structural integrity, allowing the tapered design to provide stress concentration compensation without sacrificing damage tolerance.
Solution Approach 2:
The patent implements preliminary action by pre-forming the filler edge geometries on composite strips before assembly. This ensures that when strips are laid up in tapered zones, the gap-preventing geometry is already in place, proactively preventing gap formation rather than attempting to correct it after assembly. This is particularly important in complex tapered regions where post-assembly gap correction would be difficult.
3Ease of manufacture
If straight cuts are used at transverse ends of composite strips, then manufacturing is straightforward, but resin pockets and gaps form at the ends
Solution Approach 1:
The patent applies parameter changes by modifying the geometric parameters of the transverse ends of composite strips. Instead of straight 90-degree cuts, the filler edges are cut at angled (chamfer or bevel) or curved geometries. These parameter changes in cut angle and profile prevent resin pocket formation at strip ends while remaining compatible with conventional cutting equipment and processes.
4Reliability
If filler edges with non-straight geometries are used, then gaps between adjacent strips are prevented, but manufacturing complexity increases
Solution Approach 1:
The patent minimizes manufacturing complexity by applying complex filler edge geometries only locally at interfaces between adjacent plies where gaps occur, rather than throughout the entire composite structure. This selective application maintains simplicity in the majority of the structure while providing gap prevention only where needed.
Solution Approach 2:
The patent uses curved filler edge geometries that, while more complex than straight lines, follow simple convex or concave profiles that can be efficiently manufactured using conventional CNC routing or waterjet cutting. The curvature provides superior gap prevention compared to straight edges, particularly in rounded corners and transition zones, while remaining manufacturable with standard equipment.
Data Source
Figure 1A
Figure 1B~1D
Figure 2~4
AI summary
In accordance with at least one aspect of this disclosure, a composite structure can be formed of or including a plurality of composite strips (151). The plurality of composite strips (151) include one or more filler strips (153) which can have at least one filler edge (155) having a filler edge geometry between a first surface (157) and second surface (159), the second surface (159) being opposite the first surface (157). The filler edge geometry can be configured to prevent formation of one or more gaps between one or more adjacent composite strips.