CARBON EXPLAINED

Seldén section structure
All Seldén sections are filament wound. Each section is available in two wall thickness’s with additional reinforcement of Uni-directional tape in key strength areas (tapered top masts for example) gives us 6 inertia options per section size. This extensive set of options enables us to optimise the inertia ratio for specific requirements. Seldén Process
Individual carbon fibres are very light but fragile. For their weight, they are very strong in tension. To make a structure, the fibres are brought together and held firmly in resin. To help handling, the fibres are made into different types of raw materials for manufacturers of large components. We use four types of raw material:a. Pre-preg Tow. This is thin ribbon made from bundles of plain fibres held together by uncured resin. b. Pre-preg UD Tape. This is a wide tape formed in the same way as tow. Applied externally by hand in long strips.c. Pre-preg cloth. A woven cloth made from tow. Applied externally by hand in multi layer reinforcement patches. d. E-glass. Pre-peg fibreglass used internally as an insulating layer where aluminium components may be fitted. Manufacture
The basic tubes are wound over a male mandrel. The mandrel rotates on a large 4 axis CNC lathe, and a delivery head moves in a pre-programmed pattern along a track to lay fibres onto the surface.The pre-preg carbon tow is applied under tension, the layup pattern is driven by a programme which interprets the mast requirement. Layers are built up at various angles to the mandrel axis. UD tape and reinforcing patches are applied during the filament winding process.At this stage, despite the tow being wound under tension, the layup is not consolidated. If heated at this stage it would produce a relatively low density laminate. The secret to making a strong laminate is to apply the correct pressure to squeeze the laminate together at the same time as applying heat to cure the resin. To do this, heat shrink tape is wound onto the outside, using the filament winding head. The whole mandrel/ laminate/heatshrink tape combination is then put into a vacuum bag and setup for cure in the autoclave. The temperature and pressure are increased, maintained and then reduced in a tightly controlled manner.As the temperature increases, the mandrel expands and the tape shrinks. This, together with the increased pressure from the autoclave, squeezes the laminate as it cures with the heat. The resulting laminate is really well consolidated, with virtually no void content.The cured assembly is allowed to cool, removed from the autoclave, then removed from the mandrel using hydraulic power. 8 Photo courtesy of © robrowephotography.co.uk