Metallic-Composite Joint Liner for Lower Stress Load Transfer
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Solution Overview
Problem
The challenge lies in implementing strong joints for load transfer from composite members to metallic parts in aircraft systems, where conventional methods often compromise the strength of composite materials, and existing solutions fail to effectively manage stress concentrations and weight reduction in metallic/composite joints.
Innovation Solution
The use of liners made from elastic polymers or fabrics with reduced compressive stiffness, positioned between the composite and metallic members, to alleviate stress concentrations and facilitate load transfer, while avoiding methods that weaken the composite material, such as threading or drilling, by compressing the composite member between the metallic member and an insert.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metallic materials are used for actuator components, then strength and complex geometries are achieved, but weight increases
Solution Approach 1:
The patent employs fiber-reinforced polymer-matrix composites (PMC) to replace traditional metallic materials in actuator components. The composite rod elements with flared or angled ends provide both strength and weight reduction, achieving a balance between mechanical performance and weight requirements for aircraft landing gear systems.
2Weight of moving object
If composite materials are used to reduce weight, then weight is reduced, but joint strength for load transfer deteriorates
Solution Approach 1:
The patent introduces liner elements as intermediary components between the composite rod elements and metallic parts. These liners facilitate effective load transfer from composite to metallic components while preserving the weight advantages of composite materials, solving the joint strength problem without compromising weight reduction.
Solution Approach 2:
The composite rod elements are pre-formed with flared or angled ends before assembly. This preliminary shaping creates optimized stress distribution patterns that enhance joint performance and load transfer capability, addressing strength requirements before the actual assembly process occurs.
3Reliability
If conventional joining methods are used, then connection is achieved, but stress concentrations and composite material strength are compromised
Solution Approach 1:
The patent eliminates traditional joining methods that involve threading or drilling operations on composite materials. By extracting these harmful joining processes and replacing them with compression-fit assemblies using liners, the composite material integrity is preserved while reliable connections are still achieved.
Solution Approach 2:
The patent changes the joining approach from mechanical fastening (threading/drilling) to compression-based assembly. This parameter change in the joining mechanism avoids stress concentrations and material removal, maintaining composite strength while achieving reliable connections through the liner-mediated compression fit.
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 significantly reduces maximum shear stress by up to 56% and enhances the structural integrity of the joint, allowing for efficient axial load handling without compromising the composite material's strength, thus addressing the weight reduction and stress concentration issues in metallic/composite joints.
Implementation Method 1
The one of the flared end or the angled end is compressed between the metallic member and the insert
Implementation Method 2
alleviate stress concentrations
Implementation Method 3
The liners may comprise at least one of an elastic polymer (elastomer), a polymer, or a fabric. A stiffness of the liners may be less than a stiffness of the composite member
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A metallic/composite joint may comprise a composite member (210) having a flared end (212) or an angled end, a liner (240) perimetrically surrounding the composite member, and a metallic member (220) perimetrically surrounding the liner. A first side of the liner contacts the composite member and a second side of the liner contacts the metallic member. The liner perimetrically surrounds at least a portion of the flared end. A through-thickness compressive stiffness of the liner may be less than a similar stiffness of the composite member.