This work evaluates the use of structural aspects in the manufacture of drum shells based on their modal behavior. The drum shells are made of composite carbon fiber-reinforced epoxy (CFRE) due to the structural variables commonly used in the industry for the manufacture of these musical instruments. Musicians consider the shell of a membranophone to be responsible for the differences in timbre between different instruments. Normally, this variation focuses attention on the mechanical characteristics of the material and on the overall thickness of the cylinder that forms the shell. Some manufacturers, especially those that use metals and composites, resort to low thicknesses, below 2 mm, which forces them to use structural reinforcements at the edges of the cylindrical shell to avoid deformations due to the tension generated by the membranes. As shown in this research work, these structural elements have great relevance within the acoustic behavior of the drum shell. Comparisons are made among the frequencies obtained for the different vibrational modes by using finite element simulations, establishing the length of the structural solution previously mentioned and the number of plies of composite laminate as design variables, starting from the characteristics of a real case constructed with CFRE and concluding with experimental validation. The range of study is limited to the values of the frequencies generated by the membranes. The results demonstrate that the use of different manufacturing variables can lead to savings in production costs without compromising the modal behavior of the shell.

Composite materials are presented in a wide variety of industrial sectors as an alternative to traditionally used materials. In recent years, a new sector has increasingly used these kinds of materials: the manufacture of musical instruments. Resonances of different elements that make up the geometries of musical instruments are commonly used with the aim of enhancing aspects of the timbre. These are sensitive to the mechanical characteristics of the material, so it is important to guarantee the properties of the composite. To do this, it is not uncommon to use pre-impregnated fibers (prepregs) which allow fine control of final volumetric fractions of the composite. Autoclaving is a high-quality process used to guarantee the desired mechanical properties in a composite, reducing porosity and avoiding delamination, but significantly raising production costs. On the contrary, manufacture without autoclaving increases competitiveness by eliminating the costs associated with autoclave production. In this paper, differences in dynamic behavior are evaluated under free conditions of different Carbon Fiber Reinforced Epoxy (CFRE) prepreg boards, processed by autoclave and out-of-autoclave. The results of the complex module are presented according to the frequency, quantifying the variations in the vibratory behavior of the material due to the change of processing.

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