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Even though string musical instruments made of synthetic materials such as carbon fiber reinforced polymer (CFRP) have respected acoustic performance, but a short manufacturing cycle and low product cost, they do not become an alternative to replace high-quality string instruments made of sound woods. For CFRP violins to approach high acoustic performance wood violins, they must exhibit approximately the same bending stiffness. The CFRP is denser, stiffer, and isotropic compared to the orthotropy of wood. In this work, the acoustic behavior of CFRP violins with the same geometry as high-quality wood violins was compared. A numerical modal study was developed by finite element simulations, comparing two violin top plates, one in CFRP and the other in Picea abies (PA) wood. The simulations were developed in the ansys mechanical software, using the Block Lanczos method with a mesh of 38,216 finite volumes, finding modal patterns for both the CFRP model and the PA model. Mathematical models based on solid state physics such as effective masses and maximum vibration amplitude between models were outlined. Both models were validated against experimental studies developed by other authors. It is concluded that for instruments with the same geometry, a sonorous superiority of the wood over the CFRP was evidenced, which leads to further reinforce the unique, enigmatic, and mythical behavior of violins made of sonorous woods such as the Stradivarius violins.

This work aimed to study the tribological behavior of films composed of mixtures of nanofibrillated cellulose (NFC) and microcrystalline cellulose (MCC) at different concentrations. A microabrasive wear resistance analysis is presented as part of the tribological properties. Tribological behavior was observed against wear and tear in dry conditions. Mean surface roughness (Ra) was directly influenced by MCC concentrations in films, reaching values up to three times higher at concentrations of 30% MCC compared to films without MCC. The specific wear rate (k) of the films was inversely proportional to the MCC concentrations, observing that for low concentrations of MCC (5%), the reduction of wear was only 7% for films without MCC. Concentrations of 10% MCC the wear rate was reduced by 52%, and when passing to concentrations of 30% MCC, the reduction of wear was even more abrupt up to 95%. The specific wear rate obtained was favorable and comparable to films of synectic origin, which shows that NFC/MCC composites may offer tribological advantages such as reinforcement coatings on different materials.

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