Composite Intersection Reinforcement for Aircraft Structures
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Solution Overview
Problem
Current composite structures for aircraft, such as grid-stiffened structures, lack an efficient mechanism to transfer loads through the intersections of stiffeners, leading to increased weight and complexity due to the need for thicker skins and frames, as well as high fabrication costs and fiber distortion during curing.
Innovation Solution
A method and apparatus for manufacturing composite reinforcements using a continuous composite fiber wound in various configurations about pins, with mandrels and a cap providing support during curing, allowing for effective load transfer through intersections and reducing fiber distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If frames are mechanically fastened to the fuselage, then the structure can be assembled, but the fabrication cost becomes very high
Solution Approach 1:
The patent merges the frame and skin into a single monolithic composite structure through co-curing. The frame is formed by winding composite material over a mandrel, and the skin is then co-cured to the frame in the same autoclave cycle, eliminating separate assembly operations and mechanical fastening requirements.
Solution Approach 2:
The frame is pre-formed with integral attachment features (such as flanges and bonding surfaces) during the winding process, before the skin is applied. This preliminary formation of attachment geometry eliminates the need for post-assembly fastening operations.
2Strength
If skin thickness is increased to carry extra loads, then the load-carrying capacity is improved, but the weight and complexity of the structure increase
Solution Approach 1:
The patent uses composite materials for both the frame and skin, allowing for optimized fiber orientation and distribution. The skin is wrapped around the composite frame with fibers oriented to efficiently carry loads, achieving high strength-to-weight ratio without increasing thickness.
Solution Approach 2:
The composite skin is applied with locally optimized fiber orientations and thicknesses based on the specific load requirements at each location. High-strength regions are reinforced with additional plies or optimized fiber angles, while lower-stress areas use thinner sections, minimizing overall weight.
3Strength
If braided or woven intersections are used for composite reinforcement, then load transfer through intersections is achieved, but significant tow waviness and fiber distortion occur during curing
Solution Approach 1:
The patent extracts the intersection reinforcement from complex braided or woven configurations and replaces it with a simplified unidirectional composite structure. The frame and skin are both made from unidirectional plies that intersect at clean, straight joints, eliminating the tow waviness inherent in braided intersections.
Solution Approach 2:
The structure is segmented into distinct unidirectional composite components (frame members and skin panels) that are joined through monolithic co-curing. Each component maintains straight, aligned fibers throughout, avoiding the fiber distortion that occurs in integrated braided intersections.
4Device complexity
If longitudinal stiffeners terminate before and after each frame, then the frame structure is simplified, but the ability to control buckling is reduced
Solution Approach 1:
The longitudinal stiffeners are merged with the frame structure through monolithic co-curing, creating continuous load paths that extend through the frame intersections. The stiffeners are integrated into the frame rather than terminating, providing continuous buckling resistance without requiring additional complex attachment mechanisms.
Data Source
AI summary
An assembly and method for manufacturing a composite reinforcement for unitizing a structure are provided. According to one embodiment, the assembly includes a base having a plurality of pins extending outwardly therefrom to define a structure about which a composite fiber is wound to define a composite reinforcement preform. The assembly also includes a plurality of mandrels positioned adjacent to the base and at least a portion of the composite reinforcement preform, and a cap that is positioned over at least a portion of the plurality of mandrels. The cap is configured to engage each of the mandrels to support the mandrels and the composite reinforcement preform during a curing process to form the composite reinforcement.