Araldite composite resins from Huntsman Advanced Materials have been used by Nägeli Swiss AG to develop a trumpet bell made form  carbon fiber reinforced plastic (CFRP).

Nägeli Swiss AG makes custom metal and composite parts and develops components made of carbon fiber or glass fiber using autoclave-free prepreg processing, resin transfer moulding (RTM) or thermoforming. It makes prototypes as well as serial parts and has been involved in projects in an array of diverse industries, including aeronautics, Formula 1 and space.

In co-operation with daCarbo AG, the initiator of the project, Musik Spiri in Winterthur, the Technical University of Rapperswil and the Institute of Music Acoustics of the University of Vienna, Nägeli Swiss AG were tasked to be the first to develop a trumpet bell made from the composite material.

By making wind instruments from carbon fiber compounds, it is possible to suppress vibrations in the tube that waste energy. Instrument-makers, engineers, acoustic designers and musicians have worked together intensively to develop a trumpet and a trombone which are easier to play yet produce a warm and rounded sound.

The specific geometry of the bell gives it an exceptionally clear tone.
The specific geometry of the bell gives it an exceptionally clear tone.

Specific challenges

The trumpet bell was made using RTM technology. Dry fibers in the form of braided tapes were preformed and placed in a mold and resin was injected into the closed and heated mold. A vacuum was applied, resin injected at high pressure and after the curing cycle, the finished part was demolded.

To ensure the surface of the trumpet bell met the high quality finish required on the inner side of the bell as well as the outside, the viscosity behaviour of the resin system had to be suitable for injection under temperature and the curing cycle of the resin had to take into account that a melting core is used so that the temperature range is limited.

Another challenge lay in the geometry of the bell, which is connected with a U-bend to the metal valve engine. This geometry results in a non-demoldable core, which is why an appropriate process for melting core technology has to be developed.

Blowing energy

The composite bell reportedly allowed for measurable and noticeable lower blowing energy that is necessary for playing the trumpet. Due to the high stiffness of the instrument panel and the good damping properties of composite materials, the percentage of non-audible vibrations of the bell is reduced, therefore increasing the reflection component of the sound. Blind tests have shown that daCarbo-instruments correspond to the tone characteristic of the typical conventional trumpet sound and are readily accepted in professional orchestras.

The specific geometry of the bell also gives it an exceptionally clear tone, the companies say. The production, in contrast to the manual production of brass instruments, is largely automated, providing a constant quality, while corrosion problems from condensation are non-existent inside the instrument.

Famous musicians such as Arturo Sandoval, Jon Barnes and Roy Hargrove have tested the daCarbo trumpet and currently the trumpet bell is in serial production in three different versions, to meet the individual requirements of players.

This story is reprinted from material from Huntsman, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.