توصيفگر ها :
پانل آكوستيك , جذب صوت , اشتعال پذيري , الياف پارچه جين بازيافتي , رزين فنوليك , مدل سازي , پرتونگاري مقطعي رايانه اي
چكيده انگليسي :
Denim waste, primarily composed of cotton fibers, represents one of the most prominent types of this waste. Currently, approximately 2.3 million tons of denim clothing are produced worldwide annually. This large volume is typically discarded after one to two years of use, with only 10% being recycled, while the remaining 90% is either landfilled or incinerated. Given the high global production rate of this product, recycling denim waste has become a pressing necessity. The aim of this study is to design, fabricate, and optimize fiber panels made from denim waste and phenolic resin for use as sound absorbers in the construction and automotive industries. To this end, denim waste was processed using a garnet machine to obtain fibers. These processed fibers were then combined with phenolic resin and fabricated into panels of four different thicknesses (10, 20, 30, and 40 mm), four densities (80, 100, 120, and 140 kg/m³), and four resin percentages (20, 30, 40, and 50%) according to a response surface methodology (RSM) design using the D-Optimal approach. The morphological characteristics of the panels were examined using a field emission scanning electron microscope. The acoustic properties were assessed using a two-microphone impedance tube based on the transfer function method, while flammability rates were measured in a combustion chamber. Results indicated that the sound absorption average (SAA) and flammability rates (FA) of the fabricated panels ranged from 0.20 to 0.60 and 40 to 147 mm/min, respectively. Furthermore, sound absorption performance for all samples was predicted using Johnson-Champoux-Allard and Attenborough analytical models, with outcomes compared against experimental data. The effects of independent variables on the SAA and FA rate were also analyzed. Based on statistical indicators, including p-values, lack of fit, and the reasonable alignment between adjusted R-squared values and residual sum of squares, second-order and linear statistical models were respectively proposed to predict the SAA and FA rate. The optimal conditions were determined as achieving the highest SAA and the lowest FA rate at a thickness of 27 mm, a density of 140 kg/m³, and a resin content of 47%. Under these conditions, the SAA and FA rate were predicted to be 0.51 and 54.4 mm/min, respectively. Subsequently, three fiber panels were fabricated under optimal conditions, and their acoustic, flammability, and flexural properties were evaluated. It was observed that, with a 95% confidence interval, there was excellent agreement between the model predictions and experimental results. Additionally, three-point bending tests on the optimized panel indicated a flexural strength of 0.93 MPa. To assess the performance of the optimized panel in real-world conditions, sound absorption testing was also conducted in a reverberation room. Under these conditions, the overall sound absorption coefficient for the optimized acoustic panel was measured at 0.75. Furthermore, a simulation of the panel’s application in a multipurpose hall was conducted using Odeon software, where parameters such as reverberation time, early decay time, clarity, definition, and center time were calculated. Results indicated that the reverberation time across all frequencies was nearly linear and uniform, with an average of 0.7 seconds, well below the maximum standard threshold of 2 seconds. Other acoustic parameters also fell within ideal standard ranges. Finally, the optimized panels were installed in an anechoic chamber. Results showed that the average sound pressure level decreased from 56.5 dB to 22 dB following acoustic interventions. Additionally, the reverberation time across all frequencies was reduced to under 1 second.
