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The effects of moisture on the mechanical and acoustic properties of flax fibers embedded in polypropylene (PP) were investigated in the present study. Flax/PP and hybrid flax-carbon/PP samples were immersed in water at controlled temperatures. The water intake over time in flax/PP was shown to approach Fickian behavior at room temperature while hybrids showed strong deviations. Through hybridization with 13% carbon fibers, water uptake in flax-carbon PP was reduced by 25%. For thin hybrid laminates, positioning carbon fibers at the outer edges caused no significant difference in the rate of moisture uptake. Micrographic analysis revealed that carbon fiber bundles are more susceptible to resin deficiency in flax-carbon/PP hybrids due to its densely packed thin fibers. The stiffness of moisture-saturated flax/PP samples was 50% lower than dry specimens, with 35% increase in failure strain. The tensile strength, however, was almost unaffected, and both, dry and wet samples, exhibited similar damage characteristics. The stiffness reduction affected the acoustic performance: the resonant frequency was reduced, and the STL were lowered in the stiffness-controlled frequency domain. To determine the unknown water uptake at saturation, an accelerated method was presented as an alternative time-efficient solution for designers.

Driven by the need for sustainable eco-friendly materials, natural fibers are increasingly being used as composites reinforcements due to their low cost and their potential in meeting strength and stiffness requirements for nonstructural and semistructural applications. Fewer works, however, have been reported on the acoustic and vibration characteristics of natural fibers. In this article, the sound transmission and absorption performance of flax fiber-reinforced polypropylene (PP) composites in various configurations are assessed experimentally. Natural frequency and damping coefficient of the composites are investigated by modal analysis with an impact hammer. Results from the vibrational analysis showed that thin FF/PP composite panels have resonant frequency ranging between 300 and 1000 Hz which is consistent with the acoustic profile extracted from the sound transmission loss (STL) test. Results of STL tests revealed that higher stiffness of FF/PP composite may lead to higher STL at 100–400 Hz. Resonant frequencies of the composite range from 400 to 900 Hz and STL is show to obey the mass law with nonlinearity in the range of 900–1600 Hz. These results give a better insight into the performance of FF/PP composites in vibroacoustic environments.

Natural fiber based composites are becoming attractive candidates for use in various applications owing to their mechanical and sound absorption properties. It has been proposed that they could potentially replace glass fiber composites owing to their minimized impact on human health and the environment. Though studies have been dedicated to understanding their mechanical properties, few focus on quantifying their sound attenuation behavior. We investigated the sound absorption properties of flax/epoxy composites and found them to be superior to those of glass/epoxy composites. A noteworthy result was that the noise reduction coefficient increased from an average value of 0.095–0.11 for unidirectional flax/epoxy composite and to 0.10 for cross-ply flax/epoxy system. Results suggest that flax/epoxy composites could be less expensive, viable and ecologically superior substitutes for glass-fiber based composites, particularly in applications where sound absorption is important.

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Driven by the need for sustainable eco-friendly materials, natural fibers are increasingly being used as composites reinforcements due to their low cost and their potential in meeting strength and stiffness requirements for nonstructural and semistructural applications. Fewer works, however, have been reported on the acoustic and vibration characteristics of natural fibers. In this article, the sound transmission and absorption performance of flax fiber-reinforced polypropylene (PP) composites in various configurations are assessed experimentally. Natural frequency and damping coefficient of the composites are investigated by modal analysis with an impact hammer. Results from the vibrational analysis showed that thin FF/PP composite panels have resonant frequency ranging between 300 and 1000 Hz which is consistent with the acoustic profile extracted from the sound transmission loss (STL) test. Results of STL tests revealed that higher stiffness of FF/PP composite may lead to higher STL at 100–400 Hz. Resonant frequencies of the composite range from 400 to 900 Hz and STL is show to obey the mass law with nonlinearity in the range of 900–1600 Hz. These results give a better insight into the performance of FF/PP composites in vibroacoustic environments. [ABSTRACT FROM AUTHOR]

Natural fiber based composites are becoming attractive candidates for use in various applications owing to their mechanical and sound absorption properties. It has been proposed that they could potentially replace glass fiber composites owing to their minimized impact on human health and the environment. Though studies have been dedicated to understanding their mechanical properties, few focus on quantifying their sound attenuation behavior. We investigated the sound absorption properties of flax/epoxy composites and found them to be superior to those of glass/epoxy composites. A noteworthy result was that the noise reduction coefficient increased from an average value of 0.095–0.11 for unidirectional flax/epoxy composite and to 0.10 for cross-ply flax/epoxy system. Results suggest that flax/epoxy composites could be less expensive, viable and ecologically superior substitutes for glass-fiber based composites, particularly in applications where sound absorption is important. [ABSTRACT FROM PUBLISHER]