Polymeric Composites as Alternatives for Wood for Producing Music Instruments

In this study, the disadvantages of wood, which is widely employed in producing music instruments, are discussed. For example, high moisture sensitivity, low impact resistance, and time-consuming procedure as well as various properties of different species or in several parts of one specimen which are the main problems of wooden music instruments are extensively discussed in this paper. Many materials have been employed to replace with wood in many applications. The most successful ones are wood plastic composites (WPCs) which have been extensively applied in some fields due to their better moisture and impact resistances and low-cost producing procedure (Injection molding). But, finding a suitable alternative for wood with properties required in acoustic filed is relatively difficult since many considerations have to be noted when it will be utilized in music applications. Although wood particles, which are dispersed in wood plastic composites at high concentrations, induce wood properties to the resultant composite, they could not support all acoustic requirements throughout the composite. In this paper, a new generation based on polymeric composites is introduced as suitable alternative for wood in order to produce music instruments that could resolve the above mentioned problems of wood. Application of fiber composites possessing a structure as same as wood, has been developed due to their specific vibrational and acoustical properties. In general, such fiber composites are provided using various types of synthetic and natural fibers such as glass and hemp fibers, respectively, and different kinds of resins e.g. modified polypropylene, epoxy, and polyester resins. In this study, three different kinds of fibers (i.e. glass, carbon, and Kevlar fibers) were employed to produce fiber composites for replacing with wood in music applications. Also, an unsaturated isophthalic polyester resin was used as polymer matrix. All fiber composites were produced utilizing pultrusion method and their acoustic properties were then compared with two natural wood called white Mulberry and Cedar wood. Density and elastic modulus (in longitudinal direction) of all mentioned specimens, which are the main parameters to determine acoustic properties of a material, were measured and reported comparatively. Consequently, other acoustic parameters such as sound velocity, acoustic coefficient, sound quality factor (Q) and acoustic converting efficiency (ACE) were calculated and reported in comparison with those obtained from two kinds of natural wood. Although the results show that all manufactured composites have higher densities than those of natural wood, which reduce their acoustic efficiency, their considerable high moduli improve it increasingly. Therefore, much higher sound velocities could be obtained for fiber composites compared with wood. Furthermore, the composites demonstrate higher values of sound quality factor as well as acoustic converting efficiency in compared with those calculated for natural wood. From the obtained results it can be also deducted that carbon fiber/polyester composite possesses the highest value of acoustic coefficient among others which can be ascribed to the exceptional modulus of carbon fiber inducing to corresponding composite. The results reveal that carbon fiber reinforced polyester resin shows maximum performance and as a consequence could be undoubtedly used for making high performance music instruments.