Investigation of acoustic, mechanical, thermal, and moisture properties of milled alkali‐treated coconut tree secondary flower leaf stalk fiber‐reinforced polymer composite
Authors: Mahalingam Jayaraj , Rajendran Sivakumar , Shanmugasundram N. , Kuppuswamy Hariharan , Thirumurugan Rama 
Published: December 2023

The current research study centers on exploring natural fibers due to the increasing need for sustainable and eco‐friendly alternatives in various industries. In India, where coconut trees are widely grown for their tender coconuts and by‐products, the leftover fruit leaf stalks become agricultural waste once the coconut is harvested from the trees. So this research work involves the development of composite materials with natural fiber components by using unsaturated polyester resin (UPR) as the matrix material along with alkali‐treated coconut tree secondary flower stalk fiber (ACSF) for reinforcing. The composite materials were formed using the compression molding technique with different weight compositions of 20%, 30%, and 40% of ACSF and 80%, 70%, and 60% of UPR, respectively. From the results, the 30ACSFC reveals a maximum value of 42 N/mm2, 58 N/mm2, 10 kJ/m2, and 48 HD in flexural, tensile impact, and hardness tests, respectively. In the water absorption analysis, 20ACSFC had observed a lower moisture content, which explains the low weight percentage of ACSF in the composite. From the TGA analysis, 30ACSFC had a residual mass of 18% due to the significant change in the cellulose because of alkali, leading to strong adhesion in the composition matrix. The SAC analysis reveals that at the peak and trough levels of frequency, varying the composition of composite materials leads to improved sound absorption coefficients that surpass the performance of the 30ACSFC composite. The SEM study was carried out to identify the mechanism of failure in the elongated specimens of the tensile test, which was based on the phenomena of matrix crack, fiber pull‐out, fiber shearing, void and interfacial bonding, and de‐bonding. These results indicate the possibility of creating lightweight composites with improved strength and stiffness, making them suitable for use in roof panels, door panels, insulation, and other related applications. The incorporation of ACSF as a reinforcing material introduces new prospects for sustainable and environmentally friendly composite materials, showcasing promising mechanical and thermal properties.

Highlights

Enhanced mechanical strength: Evaluation of tensile strength, flexural strength, and impact resistance showcases how ACSF reinforcement improves the composite's load‐bearing capacity and durability.

Effective acoustic dampening: A study of sound absorption and transmission properties reveals the composite's potential in noise reduction applications, such as architectural acoustics and automotive soundproofing.

Thermal insulation potential: An assessment of thermal conductivity and expansion helps identify whether the composite is suitable for applications requiring enhanced insulation or efficient heat transfer.

Moisture resistance and stability: An analysis of moisture absorption and dimensional changes informs the composite's suitability for humid environments, ensuring its resistance to degradation and maintaining the dimensional stability.