Composite Stiffener Run-Out Drapeability via Fabric Substitution
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Solution Overview
Problem
Manufacturing composite stringers with complex geometry, such as run-out regions, often results in wrinkling and defects due to poor drapeability of non-crimp fabric layers, which can lead to stress points and reduced performance.
Innovation Solution
The use of non-crimp fabric blankets combined with woven fibre layers, where the non-crimp blankets are either dropped off or cut to form darts in the transition region, allowing only woven fibre layers in the run-out region to improve drapeability and stress performance, and a method of co-infusing and co-curing dry fabrics on a mould tool to form the stiffener without intermediate cutting steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If non-crimp fabric blankets are used in the run-out region, then load carrying performance is improved, but drapeability deteriorates causing wrinkling and manufacturing defects
Solution Approach 1:
The patent applies different fabric types in different regions: non-crimp fabric blankets are used in the constant section region where load carrying performance is critical, while woven fabric is used in the run-out region where drapeability is required to conform to the changing geometry without wrinkling. This local differentiation resolves the contradiction between strength and ease of manufacture.
2Productivity
If non-crimp fabric blankets are used throughout the stiffener, then manufacturing speed is improved, but manufacturing precision deteriorates due to wrinkling and defects in complex geometry regions
Solution Approach 1:
The patent switches from non-crimp fabric blankets to woven fabric in the run-out region where complex geometry requires high drapeability for accurate forming. This local material substitution maintains manufacturing speed while improving geometric accuracy in the critical termination region.
3Ease of manufacture
If non-crimp fabric blankets are cut to form darts to accommodate run-out geometry, then drapeability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent extracts the non-crimp fabric blankets from the run-out region entirely, replacing them with woven fabric that inherently provides the required drapeability without requiring dart cutting or other complex modifications. This simplifies the manufacturing process while maintaining ease of forming.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the manufacturability and performance of composite stiffeners by reducing defects and stress points, improving drapeability, and eliminating the need for post-curing cutting, thereby reducing costs and time.
Implementation Method 1
The fibre layers are joined together, e.g. by stitching, to form the blanket.
Implementation Method 2
a method of co-infusing and co-curing dry fabrics on a mould tool to form the stiffener
Data Source
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AI summary
A composite stiffener for a stiffener reinforced panel. The stiffener has a longitudinal direction and a run-out region which terminates at an end of the stiffener. The stiffener also has a constant section region inboard of the run-out region in the longitudinal direction and having a constant cross section transverse to the longitudinal direction with a crown between adjacent foot portions. The run-out region has a changing cross section transverse to the longitudinal direction with a crown between adjacent foot portions and the crown reduces in height towards the end of the stiffener forming a ramp. The composite stiffener comprises a number of blankets of non-crimp fabric layers.