Manufacturing and Structural Features with Respect to the Modal Behavior of a Carbon Fiber-Reinforced Epoxy Drum Shell

Abstract

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.

Review of Manufacturing Processes and Vibro-Acoustic Assessments of Composite and Alternative Materials for Musical Instruments

“…Soundboards were crafted from glass and carbon fiber-reinforced polyurethane foam [14], as well as from carbon fiber-reinforced synthetic wood [15]. A drum shell [16] and a cello [17,18] were manufactured by carbon fiber-reinforced epoxy (CFRE). Various musical instruments made from CFRE, including violin, viola, cello [19], guitar, bass, ukulele [20], snare drum [21], and piano [22], are commercially available.…”

“…Thermoset matrices generally exhibit superior mechanical properties compared to thermoplastics. In the realm of instrument making, many instruments described in the literature are manufactured using thermoset polymers, such as epoxy resin [16][17][18]. The manufacturing process for musical instruments made from fiber-reinforced thermoset polymer matrix materials typically initiates with mold preparation [27][28][29][30].…”

“…Open molding produces objects with an exposed surface, such as the soundboard of a stringed instrument [3]. On the other hand, closed molding produces objects with a closed surface in at least one direction (of the surface), as seen in the manufacturing of instruments like drums [16,29]. The means of manufacturing and the lay-up process determine the design of the mold.…”

“…Prepregs consist of reinforcement fabrics pre-impregnated with the matrix, remaining in a non-cured state. They find extensive usage in instruments manufacturing [3,4,16,28,32]. The vacuum-assisted resin transfer molding (infusion or VARTM, a subcategory of RTM) [12,17,23], stands out as the secondbest process for producing high-quality composite objects.…”

“…Some resins cure at room temperature, but high-quality resins often require specific cure cycles in ovens with specific rates of temperature rise and cooling [23,28]. Autoclaves [13,16,32] represent the most advanced version of ovens, providing controlled temperature and pressure conditions for an optimized curing process. Machining, joining, and shearingforming follow for the manufacturing of every part and the assemble of the final instrument is completed.…”