Composite Shaft Fiber Routing Around Attachment Holes
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Solution Overview
Problem
Composite shafts formed from Polymer Matrix Composites (PMCs) face challenges in interfacing with other parts due to reduced strength by volume, as standard fixings designed for metal are not suitable, leading to weight and cost increases when metal end fittings are used.
Innovation Solution
A filament wound composite fibre reinforced polymer shaft with helical wound fibres featuring at least one hole perpendicular to the axis, where fibre paths divert around the hole, allowing for reduced metal usage and maintaining structural strength by avoiding fibre cutting, enabling efficient force transmission and weight reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal end fittings are used to interface with the PMC rod, then the connection strength is improved, but the weight and cost increase
Solution Approach 1:
The invention merges the shaft body and the connection feature by forming a hole directly through the composite shaft during the filament winding manufacturing process. This eliminates the need for separate metal end fittings, thereby reducing weight while maintaining connection functionality. The shaft itself becomes both the structural element and the connection interface.
Solution Approach 2:
The invention utilizes composite materials (PMC with helical fibres) to create a shaft that can directly interface with other components. By designing the hole and fibre diversion into the composite structure itself, the shaft maintains its strength-to-weight ratio advantages without requiring dense metal fittings, thus resolving the contradiction between connection strength and weight.
2Ease of operation
If a hole is cut through the fibres to create an attachment point, then the ease of operation is improved, but the strength is significantly reduced
Solution Approach 1:
The hole is created during the filament winding manufacturing process itself, before the shaft is completed. The fibre paths are pre-calculated and pre-routed around the hole location during winding, ensuring that fibres continuously bridge across the hole region. This preliminary action maintains strength while enabling easy attachment through the hole.
Solution Approach 2:
The fibre winding pattern is locally modified around the hole region while maintaining the overall helical structure. Fibres are diverted specifically in the vicinity of the hole to ensure continuous load paths, while other regions maintain their original winding pattern. This localized adaptation preserves tensile strength while creating the attachment point.
3Strength
If fibres are diverted around the hole instead of cutting through, then the strength is maintained, but the manufacturing complexity increases
Solution Approach 1:
The hole location and fibre diversion paths are predetermined and programmed into the filament winding process before manufacturing begins. The winding machine is pre-configured with the appropriate fibre routing instructions, so that during the normal winding process, fibres automatically divert around the hole location. This eliminates the need for post-manufacturing modifications or complex assembly steps.
Solution Approach 2:
The filament winding manufacturing process is made multi-functional by integrating both shaft body formation and hole creation with fibre diversion into a single process step. The same winding machine and process that creates the shaft structure also creates the attachment hole with properly routed fibres, eliminating the need for separate operations and reducing overall manufacturing complexity.
Data Source
AI summary
A filament wound composite fibre reinforced polymer shaft comprising helical wound fibres, the shaft having at least one hole perpendicular to an axis of the shaft; wherein fibre paths of the helical wound fibres divert around the hole. The hole can be used as an attachment point to connect the shaft to other parts, e.g. by means of a pin passed directly through the hole. The amount of metal used in this type of connection can be significantly reduced compared to using metal end fittings, thus greatly reducing cost and weight of the whole system. Fibres are diverted around the hole rather than the hole being cut through the fibres which would reduce the strength of the shaft as a whole. By diverting the fibres around the hole, the fibres retain their load bearing properties and the strength of the shaft is maintained even in the presence of the hole.