Composite tension/compression strut
A composite filament-wound shaft with an end fitting mounted on an interface region on at least one end of said shaft, wherein in said interface region filaments of the filament-wound shaft are angled with respect to the shaft axis such that they follow a path with a radial component and have been cut so as to expose the ends of said filaments in said interface region; and wherein said end fitting comprises a helical thread engaging with said interface region. The helical threaded engagement provides excellent load transmission of axial forces and is therefore well suited to tension and compression elements. The joint provides a low cost and low weight interface.
1. The A composite filament-wound shaft with an end fitting mounted on an interface region on at least one end of said shaft,
wherein in said interface region, filaments of the filament-wound shaft are angled with respect to a shaft axis such that the filaments follow a path with a radial component and have been cut so as to expose ends of said filaments in said interface region; and
wherein said end fitting comprises a helical thread engaging with said interface region.
2. The shaft as claimed in claim 1 , wherein said end fitting further comprises grooves across the helical thread that break the helical thread into a plurality of part-helices.
3. The shaft as claimed in claim 2 , wherein said grooves are axial grooves or helical grooves.
4. The shaft as claimed in claim 2 , wherein said end fitting comprises four axial grooves across the helical threads.
5. The shaft as claimed in claim 1 , wherein the thread is a single-start thread.
6. The shaft as claimed in claim 1 , wherein said thread has a profile that comprises a cutting tooth portion arranged to cut into said interface region and a substantially flat land portion that frictionally engages with said interface region.
7. The shaft as claimed in claim 6 , wherein said profile further comprises at least one channel portion adjacent to said cutting tooth portion to accommodate debris produced during a mounting process.
8. The shaft as claimed in claim 1 , wherein the interface region of the shaft comprises a ramp of hoop-wound fibres that increases in thickness in the axial direction of the shaft towards the end of the shaft, and helical-wound fibres wound over said ramp.
9. The shaft as claimed in claim 8 , wherein said helical-wound fibres over said ramp have been cut or ground parallel to the axis of the shaft to expose fibre ends and form said interface region.