Hexcel's HiTape.
Hexcel's HiTape.

Launched at the JEC Europe 2013 trade show in March, HiTape is based on HexTow® carbon fibre and allows dry preforms to be manufactured in an automated process, similar to the automated fibre placement (AFP) and automated tape laying (ATL) processes widely used for UD prepregs.

Cost-effective out of autoclave (OOA) vacuum infusion or injection processes can then be used to manufacture the final product.

"This is a UD tape-type product with which you are able to get a very high volume fraction, a 58-60% volume fraction you would expect from prepreg technology, but more importantly you are able to deposit this in a very high deposition rate approaching 50 kg per hour," explains Paul MacKenzie, Hexcel VP R&T.

"After it's been layed down to provide the preform it is then infused with a resin system in order to cure off out of autoclave to make the final part."

"We see that this will provide cost improvement in terms of being able to process out of an autoclave-type environment," he continues, "but the most important characteristic about this technology, apart from its deposition rate, is the mechanical performance it delivers."

Cost savings

Hexcel says that the tight width tolerance of HiTape gives total control of the automated dry preform process – and it is a waste-free operation, even for complex structures, as the materials are placed exactly where required. There is no need to apply pressure to consolidate the preform and remove air as this occurs later when vacuum is applied.

Hexcel says customer evaluations have demonstrated that significant cost-savings are achievable with HiTape and the associated vacuum infusion process. The material allows the part design to be optimised, including function integration. The automated preform process is simplified, without any splicing of materials or polythene film to remove.

Very high preform lay-up outputs are achieved and another cost-saving benefit is that no refrigerator storage is required due to the dry nature of the reinforcements.

Mechanical properties to rival prepreg

Aircraft structures made with HiTape are claimed to demonstrate mechanical properties that are as high as those found in parts made with the latest generation primary structure prepregs.

HiTape gives particularly high Compression After Impact (CAI) performance, Hexcel reports.

HiTape has been used by AeroComposit for wing prototype components, and by Spirit AeroSystems to form the skin of an engine nacelle outer fan cowl.