In the pursuit of sustainable materials, natural fibers are gaining attention because of their renewable nature and low environmental impact. However, their application in composites has been hindered by their hydrophilicity and non-homogeneity in the properties. To address these issues, chemical treatments such as Sodium Hydroxide and Potassium Permanganate have been utilized. This study explored the impact of chemical treatments on Bamboo fibers and their subsequent influence on the vibration and acoustic properties of Carbon/Bamboo fiber-reinforced hybrid composites. This study investigates the vibration damping and acoustic characteristics of hybrid composites, considering the synergistic advantages of Bamboo’s natural damping properties and Carbon fiber’s mechanical strength. The damping factor of Sodium Hydroxide treated Bamboo fiber reinforced hybrid composites is 34.55% higher than that of untreated Bamboo fiber reinforced hybrid composites. It is also 11.95% higher than that of Potassium Permanganate treated Bamboo fiber reinforced hybrid composites. The flexural modulus of untreated Bamboo fiber reinforced hybrid composites was 164.36% and 157.77% higher than that of Sodium Hydroxide treated and Potassium Permanganate treated Bamboo fiber reinforced hybrid composites, respectively. The effect of chemical treatment on the fiber properties were analysed using the FTIR spectrum. Acoustic characterization revealed that untreated Bamboo fiber composites have higher sound absorption coefficients at lower frequencies, whereas Sodium Hydroxide-treated composites have higher sound absorption coefficients at medium and high frequencies. The results indicated that chemical treatment enhanced fiber-matrix adhesion, reduced stiffness, and influenced the damping and acoustic performance of the hybrid composites.

The hybridization reinforcements of composites allow design engineers to enhance the structural and acoustic properties of synthetic fibre-reinforced materials. Natural fibres are considered to have higher potential for replacing synthetic fibres in the composite industry. The present study aims to develop hybrid composite materials for sound insulation applications in the automotive industry. The hybrid composites were developed by reinforcing Basalt and Hemp fibres with Epoxy using vacuum bagging technique and cured under ambient conditions. Vibration and acoustic experiments were carried out on pristine and aged BHU (Basalt-Hemp-Untreated) and BHT (Basalt-Hemp-Treated) specimens. The fibre treatment and moisture gain influenced the natural frequency and stiffness of the hybrid composites. With the fibre treatment, the natural frequency of the specimens was enhanced by 12.8%. With ageing of both BHU and BHT, specimens showed a reduction in the natural frequency by 16.4% and 23% respectively. Moisture ingression into the composites reduced the stiffness and improved the damping factor of the structure. The aged BHU and BHT showed better acoustic performance compared to the pristine specimens.

Composite materials are popular substitutes for conventional materials owing to their high strength-to-weight ratio. Reinforcements in the form of woven fabric clothes are common due to their ease of availability and preparation. The use of hybrid intra-ply as reinforcements synergises the advantages of more than one type of fibre. The current work focuses on the preparation of woven carbon fibre (CF) and carbon–Kevlar (CF-K) intra-ply hybrid fibre-based composites. Epoxy resin was used as the matrix and balsa sheet was used as the sandwich material. The angle of orientation of the woven fibre cloth was varied from 0° to 45° along the direction of loading. The dynamic properties of prepared samples were experimentally investigated using an impact hammer test. The natural frequency and damping ratio were influenced by the angle of orientation and the fibre reinforcement. The CF-K hybrid composite showed better dynamic properties when compared with the CF composite. The natural frequency was highest for the 0° sample, it reduced with the angle of orientation, and a reverse trend was observed for damping ratio. Both CF- and CF-K-based composites showed similar trends. The storage modulus variation also showed a similar trend as that of the natural frequency for both types of samples with orientation, but a reverse trend was observed for loss modulus, i.e., the loss modulus increased with the change in the angle of orientation, indicating the improvement in energy storage ability of the composite.

In recent years, there has been a significant increase in the use of natural fibers as reinforcements in composites. This trend is mainly driven by their eco-friendly nature and wide availability. The objective of this research is to explore the extensive potential of combining Banana Fiber with Tyre Rubber Particles (TRP) as elastomeric fillers in natural fiber composites, focusing primarily on their applications in the automotive and aeronautical industries, particularly in terms of acoustic response. The composite sequences were named as NFC-I to NFC-V, where NFC represented Natural Fiber Composites. To thoroughly investigate the acoustic properties of these innovative composites, experimental analysis on the impedance tube was conducted along with numerical simulations on the Ansys Harmonic Acoustics^® module with Transmission Loss (TL) as the key parameter. An orthotropic material model based on the chopped fiber RVE (Representative Volume Element) was developed on the Ansys 2022 R1^® Material Designer Module which could be deemed as the novelty of the current work. From the results, it was seen that within the designated frequency bands, specifically the low (67–400 Hz), medium (400–1900 Hz), and high (1900–6300 Hz) ranges, the NFC-4 (15 wt% of TRP) composite consistently demonstrated the lowest average TL values. Conversely, NFC-3 (27 wt% of TRP) consistently showcased the highest TL values, reaching a peak of 27.13 dB in the low-frequency range and 46.73 dB in the high-frequency range. The results obtained from the impedance tube experiments align remarkably well with the numerical simulation outputs, demonstrating the reliability of the numerical model in estimating the transmission loss of composite laminatesa crucial parameter for evaluating acoustic performance.

The vibrations generated in the two-wheeled vehicles like motorcycles due to road irregularities such as cracks, potholes, and bumps on the road cause discomfort for the rider as well as the pillion. These vibrations are reported to cause lower back pains, musculoskeletal effects, fatigue, and long-term health issues. Particularly, electric two-wheelers are more susceptible to these vibrations caused by the road and need attention. This paper presents an innovative technique for the reduction of vibrations at prominent locations in the electric two-wheeler to improve the rider’s comfort. All measured accelerations are about vertical direction (along z-axis as per ISO 2631-1 standard). Passive and Semi-active damping treatments namely, Room temperature vulcanizing Silicone rubber and Magnetorheological elastomer (MRE) were applied on the test vehicle at strategic locations of vibration. Both were compared for their effectiveness in reducing the vibrations. Results showed that MRE based damping technique proved better vibration isolation at the strategic locations. The weighted root mean square acceleration as well as vibration dose values were found to decrease with the help of damping treatments thus improving the rider’s overall comfort level.