Composite Gas Turbine Shaft With Load-Fuse Spline Coupling
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Solution Overview
Problem
Conventional gas turbine engine shafts face challenges in withstanding high loads without plastic deformation or disintegration, leading to potential failure and debris release, which complicates weight, cost, and structural integrity issues.
Innovation Solution
A composite tube with a load fuse mechanism featuring metallic couplings and splines forms a preloaded interference fit, allowing the composite tube to slide past the splines during high loads, preventing failure and maintaining structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the mainline shaft is designed to withstand ultimate load, then the shaft can prevent disintegration and debris release, but the weight of the shaft, mating parts, and surrounding architecture increases
Solution Approach 1:
The shaft is divided into a composite tube section and a metallic coupling section. The composite tube is designed to withstand only limit loads, while the metallic coupling section (with higher strength) is positioned at critical locations to absorb ultimate loads. This segmentation allows the majority of the shaft to be lightweight composite material while only specific segments require the weight penalty of metal reinforcement.
Solution Approach 2:
Instead of making the entire shaft from heavy ultimate-load-capable material, the patent applies high-strength metallic coupling sections only at specific locations where ultimate loads are most likely to occur. The circumferential pitch of splines (200%-2000% of radial height) creates localized reinforcement zones that provide ultimate load protection exactly where needed, while the remaining shaft length maintains lightweight composite construction.
2Reliability
If the mainline shaft is designed to withstand ultimate load, then the shaft can prevent disintegration and debris release, but the complexity of the shaft and surrounding architecture increases
Solution Approach 1:
The patent combines the load-fusing function and the coupling function into a single integrated metallic coupling component. The metallic coupling simultaneously provides ultimate load absorption, torque transmission through splines, and mechanical coupling between composite tube sections. This merging eliminates the need for separate ultimate load absorbers, coupling mechanisms, and debris containment structures, thereby reducing overall system complexity.
Solution Approach 2:
The metallic coupling section serves multiple functions: it acts as an ultimate load absorber, a torque transmitting element, a mechanical coupling between composite sections, and a debris containment feature. This multi-functionality reduces the number of separate components needed, simplifying the overall shaft architecture while maintaining reliability under ultimate loads.
3Reliability
If the mainline shaft is designed to withstand ultimate load, then the shaft can prevent disintegration and debris release, but the cost associated with the shaft and surrounding architecture increases
Solution Approach 1:
The shaft is segmented into cost-effective composite tube sections and strategically positioned metallic coupling sections. This allows the majority of the shaft length to be manufactured from lower-cost composite materials, while expensive high-strength metallic sections are used only at critical locations where ultimate load protection is required, optimizing the overall cost structure.
Solution Approach 2:
High-strength metallic material is applied only at specific locations where ultimate load protection is most critical, rather than throughout the entire shaft. This localized application of expensive material minimizes material costs while maintaining the necessary reliability for preventing disintegration and debris release under ultimate load conditions.
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
The design prevents shaft separation and debris release, reduces weight and material costs, and enhances efficiency by decoupling axial restraint mechanisms, offering a lightweight and stiffer alternative to all-steel driveshafts.
Implementation Method 1
Each of the plurality of splines is received within and engages with a corresponding groove of the composite tube to form a preloaded interference fit between the load fuse mechanism and the composite tube
Data Source
AI summary
A shaft for a gas turbine engine includes a composite tube including a plurality of grooves extending along a longitudinal axis of the shaft. The shaft has a load fuse mechanism that has at least one metallic coupling that has a plurality of splines extending along the longitudinal axis of the shaft. Each of the plurality of splines is received within and engages with a corresponding groove of the composite tube to form a preloaded interference fit between the load fuse mechanism and the composite tube. The at least one metallic coupling includes a first portion defining a first diameter and a second portion extending from the first portion along the longitudinal axis. The second portion defines a second diameter that is greater than the first diameter. The second portion has a smooth annular outer surface devoid of any splines.