Fabrication of composite materials for improving vehicle NVH performance and investigation of properties

In this master's thesis, composite felts were produced by incorporating polymer layers between felt and interfacing materials to enhance their acoustic properties. The study utilized specially formulated felt and interfacing materials provided by Formfleks Otomotiv Yan Sanayi ve Ticaret A.Ş. The polymers selected as intermediate layers included PVA, Chitosan, Hydroxyethyl Cellulose, Carboxymethyl Cellulose, and Polieterimid. Additionally, auxiliary chemicals such as magnesium hydroxide, aluminum oxide, barite, EVA grind, and EPDM were used. The selection of these materials was informed by NVH (Noise, Vibration, and Harshness) literature and presented as a research paper.In the first phase of the study, composite felts made from the main polymer materials were formed under conditions of 180 °C, 1 minute, and 15 bar. Formability tests revealed that 100% Carboxymethyl Cellulose and 100% Polieterimidpolymers could not be formed. The formability of the other polymers yielded positive results. In the second phase, the thicknesses of the produced composite felts were measured, As a result of the measurement, it was observed that the felt thicknesses were equal, as uniform thickness is crucial for minimizing sound energy loss.In the third phase, sound tests were conducted using an impedance tube to evaluate sound absorpsiyon at high frequencies (2000-6000 Hz). It was observed that PVA polymer negatively affected sound absorpsiyon and did not function as a barrier. However, the PVA composite felt with 0.5% aluminum oxide additive achieved the highest sound absorpsiyon result. In contrast, composite felts made with 95% PVA and 0.5% EPDM exhibited lower sound absorpsiyon values.Transmission loss tests showed that rigid materials provided better results. The best performance was achieved by the composite felt with 95% PVA and 0.5% grind additives. In the composite felts made with Chitosan and Hydroxyethyl Cellulose, it was determined that aluminum oxide improved sound absorpsiyon by increasing porosity. Finally, the highest sound absorpsiyon value was obtained by reducing the aluminum oxide content.Odor and Glow Wire tests were conducted to evaluate the safety and odor properties, which are important for the automotive industry. The odor test indicated that all samples had noticeable, objectionable odors. As a result of the Glow Wire test, it was confirmed that the composite felts meet automotive standards and have the potential to fulfill safety and quality standards. This study aims to present the sound insulation properties of different polymers and additives in a detailed, comprehensive.