Hybrid Composite Tube End Fitting for Bending Load Transfer

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Solution Overview

Problem

Conventional metallic aircraft landing gear components are heavy and costly, and existing solutions struggle to effectively transfer loads between composite and metallic parts, particularly in mitigating movement and stress under axial and bending loads.

Innovation Solution

A tube arrangement featuring a composite tube with an end fitting that includes a flared portion, lobe portion, and terminating portion, where the lobe and flared portions mechanically lock the end fitting to the composite tube, reducing movement and stress through a combination of annular ridges and grooves, and the terminating portion helps in distributing loads efficiently.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If composite materials are used to substitute metallic components, then weight and cost are reduced, but joint strength and load transfer capability deteriorate

Engineering Contradiction:

ImproveweightVSAvoidjoint strength

Core Design Contradiction:

Weight of moving objectVSStrength

Solution Approach 1:

The end fitting is divided into multiple functional segments: a flared portion for stress distribution, a lobe portion for mechanical interlocking, and a terminating portion for load transfer. This segmentation allows each part to address specific load transfer requirements, thereby maintaining joint strength while using lighter composite materials.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses composite tube materials substituted for traditional metallic components, achieving weight reduction. The composite tube is配合 with a specifically designed end fitting that compensates for the lower inherent strength of composites through geometric design, thus maintaining overall joint strength.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If simple end fitting designs are used, then manufacturing complexity is reduced, but load transfer capability and stability deteriorate

Engineering Contradiction:

Improvemanufacturing complexityVSAvoidload transfer capability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The end fitting features local geometric variations including a flared portion with increased diameter for stress distribution, a lobe portion with annular ridges for mechanical interlocking, and a terminating portion for load transfer. These localized quality changes enhance load transfer capability without requiring complex overall design.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The flared portion employs curved, tapered geometry that smoothly transitions from the composite tube to the end fitting, reducing stress concentrations. The rounded contours distribute loads more effectively compared to sharp transitions, enhancing reliability while maintaining manufacturability.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Stability of the object's composition

If rigid mechanical connections are used, then movement mitigation is improved, but stress concentration and flexural shear increase

Engineering Contradiction:

Improvemovement mitigationVSAvoidstress concentration

Core Design Contradiction:

Stability of the object's compositionVSStress or pressure

Solution Approach 1:

The flared portion uses gradual curved transitions instead of sharp angles, distributing stresses more evenly across the joint. This curved geometry reduces stress concentrations and flexural shear while still providing rigid mechanical connection and movement mitigation.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The lobe portion is segmented with annular ridges that create multiple contact points with the composite tube. This segmentation distributes the mechanical interlocking function across multiple locations, reducing stress concentration at any single point while maintaining overall stability and movement mitigation.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentEP3769947B1Hybrid metallic/composite tube design to transfer bending, axial, and flexural shear

Publication Date: 2025.03.26 GOODRICH CORP

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AI summary

A tube arrangement includes a composite tube (200) defining a centerline axis, wherein the composite tube comprises a proximal surface and a distal surface, and an end fitting (304) comprising a first end (321) disposed within the composite tube and a second end extending from the composite tube, wherein an outer surface (323) of the end fitting defines a flared portion defining a terminus of the first end, a lobe portion (420) disposed axially from the flared portion, and a terminating portion disposed axially from the lobe portion, the proximal surface conforms to a geometry of the outer surface of the end fitting, the lobe portion and the flared portion mechanically lock the end fitting to the composite tube to mitigate movement of the end fitting relative to the composite tube.