Composite material for maximum sound absorption coefficient

Abstract

Composite material for sound absorption, comprising: a thermosetting polymer matrix; a natural lignocellulose fiber as reinforcement; and an industrial waste ash as filler, wherein the thermosetting polymer matrix is ​​present to about 60 wt.%, the natural lignocellulose fiber is in the range of about 20 to about 40 wt.%, and the industrial waste ash is in the range of 0 to about 20 wt.%.

Description

AREA

[0001] The present application relates to composite materials designed for improved sound absorption, in particular those containing natural fibers and industrial waste fillers in a polymer matrix for acoustic applications in mechanical engineering. GENERAL STATE OF THE ART

[0002] The state of the art for the utility model application includes various innovations in sound-absorbing materials and compositions. There is a very limited study on a material with a maximum sound absorption coefficient, produced with coconut fibers and fly ash-reinforced epoxy composite.

[0003] Existing compositions are often unable to optimally integrate industrial waste to maximize sound absorption while simultaneously addressing waste disposal and environmental concerns. Many previous materials are based on synthetic fillers or waste-free components, which limits their environmental friendliness and cost-effectiveness. Furthermore, the limited optimization of weight percentages in such hybrids restricts the achievement of peak sound absorption coefficients across broad frequency ranges. SUMMARY

[0004] The subject matter of the present invention is defined in the claims.

[0005] Currently, the expansion of industrial zones has led to a corresponding increase in industrial waste. This negatively impacts human health and the environment. This industrial waste includes fly ash, used tire rubber, rice hull ash, and other similar materials. The increasing use of industrial waste in composite materials improves the properties of these materials while simultaneously protecting the environment.

[0006] The present invention aims to reduce the problems of noise pollution and waste disposal. Therefore, the progressive use of industrial waste (such as fly ash) in coconut fiber-reinforced epoxy resin composites is investigated. The proposed material, consisting of coconut fiber and fly ash-reinforced epoxy composites, provides a maximum sound absorption coefficient. It will contribute to the ongoing research into environmentally friendly and efficient composite materials for various acoustic applications. The inclusion of fly ash as a filler in a percentage greater than zero improves the porous structure of the composite, resulting in improved sound absorption compared to composites without fly ash and promoting better noise reduction and sustainability. DETAILED DESCRIPTION OF THE INVENTION

[0007] The object of the invention is to solve the problems of noise pollution and industrial waste disposal by developing a material that maximizes the sound absorption coefficient. By incorporating fly ash, an industrial byproduct, into coconut fiber-reinforced epoxy compositions, the invention improves acoustic performance while simultaneously promoting environmental sustainability. The composite materials containing fly ash offer advantages in sound insulation, such as increased porosity and damping properties, which improve absorption in the frequency range of 63 to 6300 Hz. A component containing more than zero fly ash provides improvements in sound absorption efficiency, making the material suitable for acoustic applications such as noise barriers, flat goods, and automotive interiors.

[0008] The following sections provide a detailed description of the components, manufacturing process, and functionality of composite materials.

[0009] Materials: The fibers were collected from a local market and used as reinforcement material. These are coconut fibers, natural lignocellulose fibers extracted from coconut husks, known for their high tensile strength, low density, and inherent porosity, which contributes to sound absorption. Fly ash was sourced from the Solapur Thermal Power Station in Maharashtra, India, and used as filler. Fly ash is a fine, powdery industrial waste consisting mainly of silicon dioxide, aluminum oxide, and iron oxide, produced by burning coal in thermal power plants. It acts as a lightweight filler, introducing microporosity and thus improving sound damping. Epoxy resin and hardener were commercially sourced and used as the matrix material.The epoxy resin is a thermosetting polymer, typically bisphenol-A based, which provides strong adhesion and mechanical integrity, while the hardener is an amine-based agent that facilitates cross-linking for durability.

[0010] Alternative material implementations could include very similar natural fibers such as jute, sisal, or hemp fibers instead of coconut fibers, as these offer comparable lignocellulosic properties for reinforcement. As a filler, other industrial waste materials such as rice hull ash or bagasse ash could be included as an alternative to fly ash, providing similar silicate-based particle structures to increase porosity. The matrix could alternatively use polyester resin or vinyl ester resin—that is, thermosetting polymers with similar curing mechanisms and mechanical strengths—depending on specific cost, durability, or environmental requirements.

[0011] Fiber treatment: The raw coconut fibers were collected at a local market and manually cleaned to remove unwanted coconut husks and impurities. The fibers were washed for 8 hours and sun-dried. They were then immersed in a 5% NaOH solution (20:1 ml / g) for approximately 1 hour. After being removed from the solution, the fibers were rinsed several times with water until no NaOH remained on the fiber surface and then dried at room temperature for 24 hours. This alkaline treatment improves fiber-to-matrix adhesion by removing surface contaminants and increasing roughness, thus enhancing the overall performance of the composite.

[0012] Alternative treatments could include similar alkaline solutions such as potassium hydroxide (KOH) at comparable concentrations or enzymatic treatments for environmentally friendly surface modification to achieve analogous improvements in interfacial adhesion.

[0013] Production of composite materials: The composite materials were produced using the hand lay-up method. The composite samples were sampled in the following dimensions (250 × 150 × 5 mm) on a wooden mold. For samples containing varying weight percentages of coconut fibers and fly ash with a constant weight percentage of epoxy resin, the mold was cleaned and a layer of wax was applied inside to facilitate the removal of the compacted composite samples. The resin and hardener, in a 10:1 ratio, are used in the compositions, but first, the epoxy resin and the required amount of fly ash were mixed with a mechanical stirrer until a homogeneous slurry was formed. To obtain a homogeneous final mixture, the hardener had to be added to this slurry and stirred again.The mixture of epoxy resin and fly ash was prepared and poured onto the surface of the mold. Fibers were then added to the mixture. The resin was distributed within the fibers using a roller, and this process continued until both were visible. The samples were then compressed with a 30 kg load for 24 hours and subsequently cured for 48 hours to ensure the strength of the matrix and reinforcement. Following the curing process, samples of plates, namely S1, S2, S3, S4, and S5 (as listed in Table 1), with varying dimensions according to ASTM standards, were cut for testing, including mechanical and acoustic absorption tests.

[0014] Alternative manufacturing methods could include compression molding or vacuum-assisted resin pressing to improve uniformity, the use of similar weight ratios and curing conditions for scaled-up production, or improved fiber impregnation. Table 1 sample symbol Epoxy resin coconut fiber fly ash S1 E60: C40: F0 60 40 0 S2 E60: C35: F05 60 35 05 S3 E60: C30: F10 60 30 10 S4 E60: C25: F15 60 25 15 S5 E60: C20: F20 60 20 20

[0015] The sound absorption coefficients of various weight percentages of coconut fiber / fly ash composites are measured at frequencies ranging from 63 to 6300 Hz to obtain an optimal composite material with a high sound absorption coefficient. The integration of fly ash contributes to a more porous microstructure, which scatters and dissipates sound waves more effectively, resulting in higher absorption coefficients, particularly at mid to high frequencies. This makes the composites advantageous for soundproofing in industrial, architectural, or automotive environments, reducing noise pollution while utilizing waste materials.

[0016] The material described herein integrates sustainable materials and an innovative composition to combat noise pollution and reduce waste. With varying weight percentages of coconut fibers and fly ash in an epoxy matrix, it provides improved sound absorption, thus contributing to environmentally friendly acoustic solutions.

Claims

[1] Composite material for sound absorption, comprising: a thermosetting polymer matrix; a natural lignocellulose fiber as reinforcement; and an industrial waste ash as filler, wherein the thermosetting polymer matrix is ​​present to about 60 wt.%, the natural lignocellulose fiber is in the range of about 20 to about 40 wt.% and the industrial waste ash is in the range of 0 to about 20 wt.%. [2] Composite material according to claim 1, wherein the thermosetting polymer matrix comprises an epoxy resin, the natural lignocellulose fiber comprises coconut fibers and the industrial waste ash comprises fly ash. [3] Composite material according to claim 1 or 2, wherein the industrial waste ash is present in a proportion greater than 0 wt.% to improve sound absorption. [4] Composite material according to any of the preceding claims, wherein the natural lignocellulose fiber is alkali-treated. [5] Composite material according to any of the preceding claims, wherein the thermosetting polymer matrix is ​​mixed with an amine-based hardener in a ratio of 10:

1. [6] Composite material according to any of the preceding claims, produced by the hand-laying method and hardened under pressure.