North TPT®(Thin Ply Technology®)
The carbon fibre now branded Thin Ply Technology, or TPT, is born from the leading edge sail materials technology developed by Createx of Cossonay, Switzerland for the 2007 America’s Cup.
This sail technology was acquired by North Sails after the Cup and the thin ply process refined to become ‘3Di’, the highest performing sail technology currently available.
Mid-2009, the company's technical team decided to apply some of the 3Di materials processing knowledge to ‘rigid’ carbon fibre-epoxy composites. An extensive development programme followed, covering resin chemistry, tape processing, tape laying techniques, lamination methodology and the resulting laminate properties.
What is TPT?
Comparing conventional carbon and TPT
TPT carbon is essentially extremely lightweight unidirectional pre-preg plies (down to 25 grams per square meter, or gsm, fibre weight). By way of comparison, ply weights of 150–600 gsm are typically used at present in the construction of structural composite parts in the marine industry and elsewhere.
Lightweight plies cannot be ‘hand laminated’ due to their fragile nature. A ‘plotter’ (automated tape laying machine) is used to build up multi-ply ‘complexes’ which are then transferred to a mould for consolidation and cure. Use of the plotter and its associated design software results in much higher levels of ply positional accuracy than was previously possible. The designer can also produce a much more ‘finely tailored’ laminate than in the past. The position, extent and angle of every piece of tape are prescribed at design time. An integrated QA system ensures that every piece is placed to specification.
The materials created using the TPT process can be applied to any of the usual pre-preg moulding processes (male or female moulding, roll wrap, mandrel winding etc.) Carbon fibre grades - from standard modulus (235GPa) through high modulus (380GPa) to ultra high modulus (440GPa +) - are able to be used in the process.
Why TPT is better
Four performance gains
The TPT process enables materials performance gains in four areas :
1. Optimised resin properties
The resins used in TPT have been specially developed to take advantage of the characteristics of lightweight plies
2. The 'Thin Ply Effect'
Studies have shown that thinner plies within a laminate have greater strength than thicker ones. This effect applies to static properties as well as impact and fatigue.
3. Optimised ply angles
With the increase in the number of plies in a laminate and the creation of custom 'complexes' comes the opportunity to use whichever ply angles are best for the loading situation at every point on the part.
4. Optimised part thickness
Thinner plies and custom complexes also give the opportunity to produce smooth tapers in part thickness to exactly match local loading.
The result is a lighter stronger composite part with the following characteristics:
- Compressive increase 15-20%
- Improved notch strength 15-30%
- Fatigue properties increased
- Finer tolerance laminate placement/patching and tapers
- Conservative weight savings over conventional materials/processes:
- 6-10% in a standard mast
- 8-12% in standard boom
- 10-25% in standard spreader