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HexPly® M79 prepreg for wind turbine blades

News International-French

25 Feb 2013

JEC Europe 2013 - The new HexPly® M79 prepreg from Hexcel is a potential game-changer in the wind blade industry - offering a real option for those who currently manufacture blades by infusion to move to prepreg technology and benefit from superior mechanical performance.

HexPly M79 has been developed by Hexcel’s R&T chemists and engineers to respond to the industry requirements for a lower temperature curing prepreg that cures more quickly than products currently on the market. A number of cure cycle options are possible, providing great versatility. For a very low temperature cure, a cycle of 10 hours at just 70°C is recommended. This enables lower cost tooling and associated materials to be used and results in energy savings, creating a highly competitive cost environment. If a more rapid cure cycle is required, then the prepreg can cure in 8 hours at 75°C and in only 4-6 hours at 80°C. This is a significant time-saving on established industry prepregs where a typical cure cycle for an 80°C curing resin matrix is 10 hours.


With HexPly M79, there is also much less risk of an exothermic reaction (a 60% reduction on Hexcel’s standard M9G prepregs) yet the prepreg is based on the standard epoxy chemistry that has over 20 years of proven performance for wind blade manufacture. An additional benefit is that the new prepreg has a very long outlife at room temperature of at least 2 months, which is unusual for such a low temperature curing product.


The low cure temperature of HexPly M79 gives the added benefit that the system is totally compatible with any liquid epoxy resin used for infusion processing. This means that the prepreg and infusion processes can be combined in the same blade, combining the twin advantages of stronger laminates and cost-effective processing.


The ultimate performance for wind blades is achieved when HexPly M79 is reinforced with carbon fibre to provide exceptionally strong laminates that are lighter than those made with glass fibre. HexPly M79 with carbon fibre reinforcements is an enabling technology for the increasingly larger wind blades that are being manufactured – now approaching 100m in length.


For these super-size blades, Hexcel’s innovative and patented carbon UD materials utilizing Grid-Technology allow very thick carbon UD laminates to be manufactured using vacuum bag technology, resulting in excellent void-free laminate quality. The technology assists in removing air during the vacuum bag process and ensures that the void content in the final unidirectional carbon laminate is very low, giving superior mechanical performance by translating carbon fibre properties into laminate properties. Hexcel’s HexPly carbon fibre UD prepregs with grid technology have been certified by Germanischer Lloyd for use in wind energy applications.


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Booth G57