Composite Lobe Joint Geometry for Thin-Wall Drive Shaft Assembly
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Solution Overview
Problem
The challenge lies in designing composite drive shafts with thin walls for weight efficiency while maintaining structural integrity and reliability, particularly in aircraft applications, where traditional methods using fasteners for joining dissimilar materials are weight-intensive and time-consuming.
Innovation Solution
The method involves using a removable mandrel with a lobe joint member and end flange assembly, applying composite materials via Automated Fiber Placement or Tape Laying, and integrating lobe joint members with tapered portions to form a composite drive shaft without the need for fasteners, ensuring torque and axial force transmission through the geometry of the lobes and tapered surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional fastener-based joining methods are used for dissimilar materials, then structural integrity and reliability are maintained, but weight increases and manufacturing time becomes excessive
Solution Approach 1:
The lobe joint member integrates multiple functions into a single component: it provides load transfer between dissimilar materials, eliminates the need for separate fasteners, and creates a monolithic structure that combines the advantages of both metallic and composite materials. The lobe geometry with tapered portions merges the joining function with the structural component itself.
Solution Approach 2:
The invention extracts and eliminates the fastener elements from the traditional joint design. By removing fasteners, holes, and associated assembly hardware, the design achieves weight reduction while maintaining structural integrity through the lobe geometry that directly transfers loads between components.
2Reliability
If traditional fastener-based joining methods are used for dissimilar materials, then structural integrity and reliability are maintained, but manufacturing time becomes excessive
Solution Approach 1:
The lobe joint member is pre-formed with integrated lobe geometry and tapered portions before assembly. This preliminary formation of the joint structure eliminates the need for time-consuming operations such as drilling holes, inserting fasteners, and tightening during final assembly, thereby reducing manufacturing time while maintaining structural integrity.
3Reliability
If wall thickness is increased to maintain structural integrity, then reliability improves, but weight increases
Solution Approach 1:
The lobe joint member applies local quality by concentrating material thickness where it is most needed for load transfer. The tapered portions and lobe geometry provide increased material density at critical stress points while allowing thinner walls in non-critical areas, optimizing the balance between structural integrity and weight reduction.
Data Source
AI summary
Methods of making composite drive shafts and manufacturing assemblies thereof are provided. The methods include providing a removable mandrel having a cylindrical shape and assembling a lobe joint member at an end thereof. The lobe joint member includes at least three lobes equally distributed thereabout. A removable end flange is assembled to the lobe joint member at an opposite end of the lobe joint member from the removable mandrel to form a manufacturing assembly. A composite material is applied to an exterior surface of the manufacturing assembly to form a composite tubular that includes the lobe joint member at an end thereof. The removable end flange is removed from the lobe joint member and the removable mandrel is removed from within the composite tubular to form a composite drive shaft comprising the composite tubular and the lobe joint member integrally formed at an end of the composite tubular.