Abstract
To test the acoustic performance of fiber-reinforced composites for replacing wood, an acoustic vibration test method is developed. For evaluation of the test method, composites are manufactured using hemp and ramie embedded in epoxy, through vacuum-assisted resin infusion molding. The effects of the most important factors, i.e., impulse, relative humidity (RH), and specimen thickness, on the acoustic vibration response of the composites are systematically studied. The magnitudes of the impulses, represented by different masses of the dropping balls, seem to have little influence on the shapes of the acoustic vibration curves, although the intensity of the spectra increases as the impulse increases. The RH influences the spectrum shape significantly due to variation in the Young’s modulus and density of the material upon absorption of moisture. The specimen thickness also greatly affects the testing results. The specific dynamic modulus, acoustic radiation damping coefficient, and acoustic impedance change a little as the impulse magnitude and RH change, but decrease substantially as the specimen thickness increases. The specific dynamic modulus can be linearly correlated with the flexural modulus of a material.
Highlights
The acoustic properties of fibrous materials and fiber-reinforced composites have been extensively studied for the purpose of sound insulation and absorption [1,2,3,4,5,6,7]
Liang and coworkers [12] used a combination of X-ray micro-computed tomography (Micro-CT), acoustic emission (AE), and digital image correlation (DIC) techniques to evaluate the damage initiation/evolution of hybrid 3D woven composites
No scientifically sound method has been reported for testing the acoustic emission properties of composite materials, for percussion musical instruments, which are often assessed by musicians’ subjective evaluations
Summary
The acoustic properties of fibrous materials and fiber-reinforced composites have been extensively studied for the purpose of sound insulation and absorption [1,2,3,4,5,6,7]. Liang and coworkers [12] used a combination of X-ray micro-computed tomography (Micro-CT), acoustic emission (AE), and digital image correlation (DIC) techniques to evaluate the damage initiation/evolution of hybrid 3D woven composites. Jalili and coworkers [16] have studied the acoustic emissions from carbon, glass, and hemp fiber-reinforced composites for the purpose of manufacturing musical instruments. They reported that the hemp fiber-reinforced unsaturated polyester composites had acoustic properties closest to those of poplar, walnut and beech wood specimens. Designing a scientifically sound, easy-to-use, and highly repeatable method for acoustic vibration tests of composites for percussion musical instruments could be critically important for material evaluation, selection, and improvement. We have to determine how these factors may influence the test results
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