Absorption Properties Of Composites Research Articles

The microwave absorption properties of soft magnetic materials in frequency up to 40 GHz

With the continuous development of communication technology, the microwave frequency used has been extended to 24∼30 GHz or even higher. Thus, for the research on microwave absorption materials, the commonly used 2∼18 GHz frequency range might no longer be enough. More studies of microwave absorption properties in a higher frequency band are necessary. In this work, we report the microwave absorption properties of several soft magnetic composites in frequency up to 40 GHz. Magnetic materials such as iron, Y2Fe16Si, Ce2Fe17N3−δ, and La2Fe4Co10B micron powders which display excellent microwave absorption properties in 2∼18 GHz, are investigated. Within 2∼40 GHz, the reflection loss (RL) of iron/paraffin, Y2Fe16Si/paraffin, Ce2Fe17N3−δ/paraffin and La2Fe4Co10B/paraffin composites could reach −46.2 dB, −71.4 dB, −49.1 dB, and −40.1 dB, respectively. Moreover, their effective absorption bandwidth (RL < −10 dB) could reach 16.9 GHz, 8.53 GHz, 10.08 GHz, and 8.03 GHz, respectively. Though the measurements are extended to 40 GHz, the absorption properties of these composites become weak when the frequency rises to around 40 GHz, which is restricted by the cutoff frequencies of the materials. The measured data shows that these soft magnetic composites are good candidates for high-frequency microwave absorption materials, while exploring magnetic materials with further higher cutoff frequencies may result in better performance.

Effects of Two Pre-Treatment Methods on Water Absorption Property of Polyester-Fibre Composites

The use of plant fibres as reinforcement in composite materials is finding increasing interest in the automotive and building industry, and the properties of plant fibre composites have been addressed in numerous research studies. The replacement of synthetic fibres with natural fibres in composites is based on their renewable and environmentally friendly nature.
 The aim of this work is to investigate the effects of two chemical pre-treatment methods on the water absorption property of polyester-fibre composites. Fully grown kenaf (hibiscus cannabalis) bast fibres were manually retted from the stalk, washed, and cut into short fibre lengths of about 10 cm. One portion of the fibres was pre-treated with 5% pbw NaOH solution before immersing it in glacial acetic acid and then in acetic anhydride. The second portion was pre-treated with 5%pbw of NaOH and 0.125% of KMnO4 in acetone. The third portion of fibres was untreated to serve as control. The ground fibre was incorporated into ortho unsaturated polyester and cast with Teflon square shaped mould. The cured samples were weighed and immersed in water at room temperature until no further gain in weight was observed. The SEM of the fibres and the composites was taken. The results showed that the acetylation pre-treatment method reduced the water absorption property of the composites by a minimum of 46.0% across all fibre volume fractions while the permanganate pre-treatment reduced it by at least 25.5%. Chemical pre-treatment of fibres can therefore

Development of Jute Fabric for Jute-Polyester Biocomposite considering Structure–Property Relationship

ABSTRACT An attempt has been made to investigate the effect of jute fabric structure, e.g., woven (plain, twill, matte), knitted, and nonwoven (parallel, cross, random laid) as reinforcement, on properties of the jute-polyester composite. The composite sheet was prepared with unsaturated polyester resin and jute fabric by hand lay-up technique using a male-female type mold. Tensile, flexural, impact, and water absorption properties of composite were measured. With the best composite based on properties, compression, shear, and hardness were also measured. Random laid nonwoven shows maximum tensile and impact strength but twill fabric produces maximum flexural strength. Matte fabric shows higher strength and lower elongation among the woven fabrics under experiment. Impact resistance and water absorption of composite from multi-layer fabric are higher compared to single-layer fabric. Composite from twill fabric shows maximum water penetration, whereas random laid nonwoven shows the lowest in similar condition. The study reveals that composite from knitted fabric is better than woven fabric but inferior to nonwoven fabric so far as mechanical properties are concerned. So, multi-layered needle punched jute nonwoven fabric from random laid web is recommended for jute-polyester composite, where higher tensile and impact strength with lower water absorption is required.

Fabrication and microwave absorption properties of the flaky carbonyl iron/FeSiAl composite in S-band

The flaky carbonyl iron powder (CIP) was prepared by high-energy ball milling, and then the CIP/FeSiAl composites were obtained with different mass ratios by ultrasonic mixing method in this paper. Here, scanning electron microscopy and Fourier transform infrared spectroscopy were used to demonstrate the microstructure and functional groups of the prepared samples. The element distribution was detected by energy dispersive spectrometer. The complex permittivity and permeability were determined by vector network analysis in the frequency range of 1–18 GHz. The reflection loss (RL) was calculated according to the transmission line theory. The composites exhibit typical flake shapes, which can exceed Snoek limit due to the enhanced shape anisotropy. The results show that the absorption property of composites can be tuned in S-band by changing the mass ratio of CIP and FeSiAl. For the composite (mass ratio of 1:4) with the thickness of only 1 mm, the RL reaches a minimum of − 6.4 dB at 2.3 GHz. Moreover, the absorption bandwidth less than − 5 dB is 2.3 GHz. This study indicates that the CIP/FeSiAl composites can be potential microwave absorbers in S-band.

Study on Sound Transmission Loss of Multilayer Composite Plate

Adoptingcomposite materials is the most commonly used method for noise control. Thispaper deals with the analysis of the sound absorption property ofcomposite materials. A multilayer composite plate with five layersis analyzed in ANSYS. A Fluid-structure coupled finite element model isestablished with air as the fluid backing. By solving the finite elementequations, the characteristic of the material transmission losses in low andhigh frequencies is obtained. Moreover, the influences of the material parametersinclude density and Young's modulus on the transmission losses are analyzedwhich can provide basis for the design of the absorption composite materials.

Sound-Absorbing Properties of Kapok Fiber Nonwoven Composite at Low-Frequency

More and more concern for environmental problems has led public to use natural and environmentally benign sound-absorbing materials. In this study, the sound-absorbing nonwoven composites based on kapok fiber and hollow polyester fiber were developed and sound absorption properties of kapok fiber nonwoven composites were investigated in the low frequency region of 100-500 Hz using the impedance tube method. The poor sound-absorbing at low-frequency is one of the difficult problems that urgently need to be solved in fibrous sound-absorbing materials. The effects of physical parameters, including bulk density and thickness, and depth of back cavity on sound absorption properties of composites were studied. Increasing of the bulk density, thickness and depth of back cavity is contribute to improve sound absorption properties of composites at low frequency. The comparisons of kapok fiber with polypropylene (PP) fiber and hollow polyester fiber indicated that as a natural fiber, kapok fiber had a superior acoustical properties at low frequency.

Effect of air bubbling and ultrasonic processing on water absorption property of banana fibre-vinylester composites

The effect of alkaline treatment in combination with air bubbling in banana fibre mat on the water absorption property of the fibre composite has been experimentally studied. The effect of sonication on the water absorption property of the composites is also studied. Hot-water immersion test is done on the samples. Water uptake was quantified for the composite disc under different processing conditions. The studies have revealed that the fibre surface modification rate is enhanced by the combination of air bubbling with the general process of alkaline treatment. Water absorption is highly reduced by the sonication process. This shows the importance of this method of fibre treatment and this shall encourage other researchers to develop an adequate system to expedite fabrication for better quality of woven banana fibre composites for various sectors such as household utility or automobile parts.

The Physical Properties of Oil Palm Empty Fruit Bunch (EFB) Composites Made from Various Thermoplastics

Oil palm empty fruit bunch (EFB)-based composites were produced using different types of thermoplastic as matrices. The composites were produced by using an internal mixer. The mechanical and water absorption properties of composites were investigated. Overall, the incorporation of EFB into the polymer matrix has resulted in the reduction of flexural strength. The poor performance has been attributed to the poor filler-matrix interaction. Both flexural and tensile modulus of PE and PP composites have been improved upon the addition of fillers, however, both PS and PVC composites showed a decreasing trend. Tensile strength and elongation at break results for all composites have been reduced as the result of incorporation of filler. This has been attributed to the poor filler-matrix interaction or compatibility, size irregularity and also decreased ductile deformation. Water absorption and thickness swelling increased as the filler loading is increased. This has been attributed to the presence of hyrophillic hydroxyl groups of the filler.