Hybrid Metallic-Composite Joint With Integral Bearing Load Path
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Solution Overview
Problem
Aircraft retractable landing gear systems face challenges in efficiently transmitting structural loads between metallic and composite components, requiring an optimized load path to manage axial, compressive, and bending loads while minimizing weight.
Innovation Solution
A metallic-composite joint fitting is designed with a composite structure, an integral bearing featuring frustoconical portions, a sleeve with a cylindrical bearing surface, and a metallic end fitting, where the externally threaded portion has a smaller diameter than the bearing portion, allowing for effective load distribution through threaded and non-threaded surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If composite tubes are used to interface between metallic structures, then component weight is reduced, but load transmission efficiency between metallic and composite components deteriorates
Solution Approach 1:
A metallic bearing is introduced as an intermediary component between the composite tube and metallic end fitting. The bearing includes frustoconical bearing surfaces that interface with the composite tube and a cylindrical bearing surface that interfaces with the metallic end fitting, creating an optimized load path that efficiently transmits loads between dissimilar materials while maintaining weight benefits of composite construction
Solution Approach 2:
The solution employs a hybrid metallic-composite construction where a composite tube with flared end portions is combined with a metallic bearing and metallic end fitting. This composite approach allows each material to be used where it provides optimal performance: composite for weight reduction and metallic for load-bearing interfaces
2Productivity
If working loads are transmitted directly through the composite structure, then load path optimization is achieved, but structural integrity under bending loads deteriorates
Solution Approach 1:
The metallic bearing acts as a mediator that receives loads from the composite tube through its frustoconical bearing surfaces and redirects them through its cylindrical bearing surface to the metallic end fitting. This intermediate metallic structure protects the composite tube from direct bending loads while maintaining an efficient load path
Solution Approach 2:
The bearing design features different geometric characteristics in different regions: frustoconical surfaces where they contact the composite tube to match the flared geometry and distribute loads, and a cylindrical surface where they contact the metallic end fitting. This local differentiation optimizes load distribution at each interface while maintaining overall structural integrity
Data Source
AI summary
A metallic-composite joint fitting is provided. The fitting may comprise a composite structure, an integral bearing comprising a first frustoconical portion and a second frustoconical portion each having a complimentary shape to the composite structure, a sleeve comprising a third frustoconical portion coupled to a cylindrical bearing surface of the integral bearing, and a metallic end fitting coupled to the third frustoconical portion, wherein the metallic end fitting comprises a bearing portion contacted with the cylindrical bearing surface.