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5th March 2020, Milan

Pitch fibre and induction heating to increase tooling efficiency

© GP Marketing Consulting Sas.© GP Marketing Consulting Sas.

GP Marketing Consulting Sas, in collaboration with the Polytechnic of Milan, Plyform Composites srl and Corebon AB, has developed an innovative tool made of high-modulus pitch carbon fibre, combined with induction heating technology, to study its possible industrial applications.

Sumitomo Corporation Europe, the official European distributor of Mitsubishi DIALEAD  pitch fibres, supplied the fabrics used in the production, in particular, the balanced plain weave fabric UHM 636 P for the core and spread-tow UHM DYF 15-150 T for the outer layer, both made with DIALEAD K13916 pitch-based fibre. These fabrics were compared with PAN-based fabrics normally used for moulds, with the same weight and impregnated with a tooling resin system made by Technologycom srl.

According to GP Marketing, pitch-based carbon fibres are particularly interesting for their mechanical and thermal properties, since their molecular composition can reach up to 99.9% of carbon and can exceed 900 GPa of elastic modulus; the molecular structure is also highly oriented, also by virtue of the initial melt spinning, during which the precursor is pulled while being heated. This process as has a result an excellent thermal conductivity, up to 800 W/(m*K) (copper ≈ 400 W/(m*K)).

“An extensive experimental campaign was carried out to evaluate the mechanical and thermal properties of both pitch-based and PAN-based carbon fibre. The latter was used as a reference to compare the results, which demonstrated the higher properties of the pitch-based carbon fibre in both aspects; particularly the elastic modulus reached a 300% increase compared to the PAN-based fibre,” the company explains.

© GP Marketing Consulting Sas.© GP Marketing Consulting Sas.

“A classic LTC 1-8-1 sequence with core 〖"[0/+45/-45 /0]" 〗_"s"  was adopted to manufacture the moulds. The pitch-based carbon fabric showed a good drapability and an easy handling, with no issues whatsoever. The thermal tests in autoclave gave very good results and the induction heating, used in the next step of the project, clearly demonstrated a better thermal behaviour of the pitch tool compared with the PAN one.”

“Induction is a contactless method consisting in heating directly all electrically conductive materials through the electromagnetic induction principle. With an ad hoc inductor, the heating area can be located or distributed both on the surface and throughout the thickness of the composite in a completely customizable way, allowing a complete thermal volumetric control.”

“In our case, the coils were applied directly on a backing structure under the surface of the mould. This type of solution enables an even heating of the entire surface of both moulds. Looking at the thermo-camera videos, it is easy to notice that after only 4 minutes the pitch-based mould had completely reached the operating temperature, unlike the PAN-based mould, which was unable to reach the set temperature,” GP Marketing adds.

© GP Marketing Consulting Sas.© GP Marketing Consulting Sas.

“So, the whole work demonstrated that it is possible to introduce and manufacture on an industrial scale such an innovative mould, which combines the mechanical and thermal advantages of the pitch-based carbon fibres with the induction heating. The result is a stiffer mould with a high level of efficiency, which can drastically reduce the length of the production cycles,” the company concludes.

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