PSI - Issue 71

Manas Samantaray et al. / Procedia Structural Integrity 71 (2025) 348–356

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2.2 Moisture absorption The water absorption test was carried out as per ASTM D570 standard. Initially the specimen was weighed and then placed inside the water. After a time interval the specimen was weighed again. The process was repeated until the water absorptivity of the specimen became zero. The water absorptivity of the specimen can be determined by the following equation =( − )⁄ x 100 (1) Where W f = Final weight of the specimen W i = Initial weight of the specimen The diffusion coefficient ‘D’ can be calculated as the slope of net gain in weight versus square root of time curve . ∞ = √ √ (2) Where M t = Mass water content at time t M ∞ = Mass of equilibrium water content T = Thickness of the sample D = Diffusion coefficient In general, the moisture resistance of natural fibre composite is very less. Mainly the water may enter the micro gaps between the different polymer chains or water may penetrate in the gap between the fibre and matrix interface or may enter the micro cracks of the composite.The water absorption properties of the developed composites were evaluated using the diffusion coefficient analysis, which is a crucial feature for materials used in automotive applications where exposure to moisture can impair durability and mechanical performance. According to the study, the equilibrium water content marginally rises because of the moisture affinity of natural fibres, but the diffusion coefficient drops as the fibre volume fraction increases, suggesting that a larger fibre content gradually reduces water intrusion. According to these results, composites with larger fibre percentages are better suited for automotive settings since they are less likely to absorb moisture. This study aids in the creation of composites that strike a balance between mechanical performance and moisture resistance, guaranteeing long-term durability in damp and humid environments by determining the ideal fiber-matrix ratios. Ever, if two images fit next to each other, these may be placed next to each other to save space. For example, see Fig. 1. 2.3 Sound Absorption Test Using a medium-type impedance tube with two fixed microphones, the sound absorption properties of the developed composite and the samples were assessed using the mean of Test Sens analyzing systems, in accordance with the ASTME 1050-98 standard method. Several acoustical properties over the frequency range of 100 – 4000 Hz were measured using the tube setup. At one end of the impedance tube is a sound source or loudspeaker. The loudspeaker's incident sound waves went down the tube, struck the sample and reflect. To find the sound absorption coefficients(α) at various frequencies, a two -channel digital frequency analyzer was used to compute the complex transfer function by measuring the sound pressure at two fixed places. This number, which ranges from 0 to 1, indicates how much sound energy the sample is absorbing. A value of α = 0 indicates no sound absorption at all, while a value of α = 1 indicates full sound absorption. The result shows that the sound absorption coefficient increases with the increase in frequency. It is also observed that above a frequency range of 1500 Hz the composite shows the best sound absorption property and it has the average sound absorption coefficient of 0.94 in between 2000 hz to 4000 hz. However, the sound absorption is less as compared to the reinforcements.