Characterization of acoustic-absorbing inter/intra-ply hybrid laminated composites under dynamic loading

This study prepared the novel laminated composites composed of a cushioning layer with double identical hybrid surface reinforcement laminates based on Kevlar fiber (KF)/carbon fiber (CF) and evaluated their acoustic and mechanical performance. The effects of reinforcing fiber type, fiber blending ratio, needle-punching frequency, and laminated sequence on the static bursting, dynamic cushioning and acoustic absorption ability of the composites were individually investigated. Results revealed that the cushioning capacity of the KF-hybrid composites was always superior to that of the CF-hybrid composites. The dynamic cushioning capacity of a hybrid composites with the cushioning layer at the intermediate position was superior to that of samples with a cushioning layer at the top and bottom positions. The CF-hybrid composites exhibited higher acoustic absorption coefficient at low (125 to 500 Hz) to mid frequencies (500 to 2000 Hz) but a lower value at high frequencies (2000 to 4000 Hz) than the KF-hybrid composites. The acoustic absorption curve and the corresponding sound absorption average were significantly affected by the needle-punching frequency. This influence diminished with an increase in needle-punching frequency. The cushioning layer at the top position enhanced the absorption ability at low to mid frequencies. Thus, the hybrid construction with a cushioning layer at the middle position and double hybrid laminated cover plies was the optimal structure for acoustic absorption.     

Sound absorbent,flame retardant warp knitting spacer fabrics: Manufacturing techniques and characterization evaluations

This study proposes a combination for reciprocal reinforcement between warp knitting spacer fabrics and PU foams. PET/Kevlar nonwoven fabrics are made with an 80:20 ratio and an incorporation of various needle-punching speed of 100, 150, 200, 250, and 300 needles/min. Ascribing to having an optimal bursting strength, sound absorption coefficient, and limited oxygen index (LOI), the PET/Kevlar nonwoven fabric that is made by 200 needles/min are selected to be combined with a glass-fiber fabric by applying needle punch in order to form a surface layer. Next, warp knitting spacer fabrics and the nonwoven fabrics are laminated, followed by being combined with polyurethane (PU) foam that are featured with different densities of 200, 210, 220, 230, and 240 kg/m³ in order to form spacer fabric/PU foam composites with multiple functions. The composites are then tested with a drop-weight test, a compression test, a bursting strength test, a sound absorption test, and a horizontal burning test. The test results indicate that all spacer fabric/PU foam composites reach a horizontal burning level of HF1, and their sound absorption coefficients at 2500-4000 Hz also suggest a satisfactory sound absorption. In particular, the optimal residual stress and compressive strength are present when the composites contain 210 kg/m³ PU foam. Similarly, the optimal bursting strength of the composites occurs when they are composed of 230 kg/m³ PU foam. The spacer fabric/PU foam composites are proven to have high strengths, sound absorption, and fire retardant, and thus have promising potentials for use as construction materials and light weight composite planks.     

Nonwoven fabric/spacer fabric/polyurethane foam composites: Physical and mechanical evaluations

In the first stage, polyethylene terephthalate (PET) fibers and Kevlar fibers are combined at a blending ratio of 80/ 20 wt% in order to form PET/Kevlar nonwoven fabrics. Two pieces of PET/Kevlar nonwoven fabrics that enclose a carbonfiber (CF) interlayer are then needle punched in order to form PET/Kevlar/CF (PKC) composites. In the second stage, the sandwiches compose PKC composites as the top and the bottom layers, as well as an interlayer that is composed of a spacer fabric and polyurethane (PU) foam. PU foams have different densities of 200, 210, 220, 230, and 240 kg/m³. These resulting nonwoven fabric/spacer fabric/PU foam sandwiches are then tested using a drop-weight impact test, a compression test, a bursting strength test, a sound absorption test, and a horizontal burning test. The test results indicate that the optimal properties of sandwiches occur with their corresponding PU foam density as follows: an optimal residual stress (240 kg/m³), an optimal compressive strength (240 kg/m³), and an optimal bursting strength (220 kg/m³). In addition, the sandwiches reach the HF1 level according to the horizontal burning test results. They also have an average electromagnetic interference shielding effectiveness of -48 dB, as well as a sound absorption coefficient of 0.5 in a frequency between 1500-2500 Hz, which indicates a satisfactory sound absorption effect. The nonwoven fabric/spacer fabric/PU foam sandwiches proposed in this study are mechanically strong, sound absorbent, and fire retardant, and can be used in construction material and electromagnetic shielding composites.     

Effects of binder fibers and bonding processes on PET hollow fiber nonwovens for automotive cushion materials

In this study, nonwoven fabrics were developed for the replacement of polyurethane foams in car interiors, in particular, cushioning materials for car seats. Polyethylene terephthalate (PET) hollow fibers and two types of bicomponent binder fibers were used to manufacture automotive nonwovens by carding processes and then post-bonding processes, such as needle punching or thermal bonding. The physical and mechanical properties of nonwovens were thoroughly investigated with respect to the effects of binder fibers and bonding processes. The tensile strength and elongation for nonwovens were found to be significantly improved by combined needle punching and thermal bonding processes. In addition, the nonwoven cushioning materials were characterized in terms of hardness, support factors, and compressive and ball rebound resilience. The nonwovens showed greater hardness than the flexible PU foam. However, support factors over 2.8 for the nonwovens indicated improved seating comfort, along with better seating characteristics of greater resilience and air permeability in comparison with the PU foam.     

Manufacturing technique and acoustic evaluation of sandwich laminates reinforced high-resilience inter/intra-ply hybrid composites

This study focused on the fabrication and acoustic property evaluation of sandwich cover-ply-reinforced highresilience thermal-bonding nonwoven hybrid composites. P-phenyleneterephthalamides and bicomponent high-resilience bonding polyester intra-ply hybrid nonwoven fabrics were compounded with glass plain fabric to produce the high strength sandwich structural cover ply by means of needle punching and thermal bonding to reinforce the whole composites and dissipate energy when being impacted. Then, the acoustic absorption properties of the homogenous intra-ply hybrid meshwork layer were investigated before and after being reinforced with the aforementioned cover ply. The influencing factors, including areal density, fiber blending ratio, needle punching depth, and air cavity thickness between back plate of the impedance tube and composites, were comparatively investigated. Results revealed that hybrid composites exhibited exceedingly high acoustic absorption properties. Acoustic absorption coefficients were promoted with increases in areal densities and fiber blending ratio of 3D crimped hollow polyester, particularly at low-mid frequency range. In addition, needle punching depths and back air cavity thicknesses considerably affected the average absorption coefficients. The meshwork center layer reinforced with sandwich structural cover-ply perform high resilience properties.     

Investigation on acoustic behavior and air permeability of struto nonwovens

This work deals with the study of acoustic performance of struto nonwovens and their relation to fabric air permeability. In order to achieve the objective of the research, sound absorption coefficient of struto nonwovens was determined via impedance tube method, the average value of sound absorption coefficient (α?) was calculated. Air permeability of struto nonwovens was examined by using FX3300 Textech Air Permeability Tester. Results showed that struto nonwoven exhibited good absorption ability at frequency bands 3000-6400 Hz while it was ineffective for frequency lower than 3000 Hz. Struto nonwovens with high GSM and fabric thickness showed better acoustic performance and lower air permeability. It was observed that α? was inversely proportional to air permeability, with correlation coefficient 0.95. It was concluded that air permeability can be used as a criterion of sound absorption behavior of struto nonwovens. A lower air permeability suggests a better sound absorption performance for struto nonwoven fabrics.     

Sound absorption properties of spiral vane electrospun PVA/nano particle nanofiber membrane and non-woven composite material

In this research, we fabricated a series of PVA membranes loaded with 0 wt.%, 1 wt.%, 3 wt.%, 5 wt.% ZrC and 0 wt.%, 1 wt.%, 3 wt.%, 5 wt.% TiO₂ using a spiral vane electrospun machine respectively. There were 2 sizes of TiO₂ nano particles: 10 nm and 200 nm. We tested sound absorption properties of needle-punched nonwovens as well as the composite of nano membranes and needle-punched nonwovens by an impedance tube at the frequency range from 500 Hz to 6500 Hz. Besides, we tested morphological characterization of nano membranes by scanning electron microscope (SEM) and crystalline properties by X-ray diffraction (XRD). We investigated the sound absorption properties of composites as well as the effect of ZrC, TiO₂, nano particle sizes and cavity depth on sound absorption properties. Results showed that sound absorption properties of composites increased at the whole range of frequency compared to those of needle-punched nonwovens. When loaded with ZrC nano particles, sound absorption properties of composite shifted to a higher frequency region, and with increasing content of ZrC, sound absorption properties were better above 2500 Hz. However, when loaded with TiO₂, sound absorption properties were better at lower frequency. With 3 wt.% TiO₂, sound absorption coefficient reached the best at the frequency range from 500 Hz to 1500 Hz. Besides, 200 nm TiO₂ was more conductive to the increase of sound absorption properties at lower frequency region compared to 10 nm TiO₂. Sound absorption properties of composites with air back cavity shifted to a lower frequency region, too. SEM showed that there was nano particle aggregation when loaded TiO₂ nano particles. XRD showed that ZrC nano particles loaded in PVA nano fiber retained their crystalline structure while TiO₂ didn’t. It appeared from the results that nano particles had an effect on sound absorption materials, with different kinds and different sizes, sound absorption properties will improve in different ranges of frequency     

The efficacy of coconut fibers on the sound-absorbing and thermal-insulating nonwoven composite board

The aim of this study is to examine the efficacy of the coconut fiber on the sound absorption and thermal insulation performance towards the composite nonwoven fabrics. The 2D polyester fiber and 12D fire retardant three-dimensional hollow crimp polyester fiber are individually mixed with 4D low-melting point polyester fiber (4DLMf) to produce 2D polyester nonwoven fabric (2D-PETF) and 12D polyester nonwoven fabric (12D-PETF) respectively. Subsequently, the coconut fiber (CF) is then laminated with the 2D-PETF and 12D-PETF to fabricate two types of PET/CF composite boards through the multiple needle-punching techniques. Accordingly, the sound absorption, thermal insulation, Limiting Oxygen Index and relative mechanical properties of the PET/CF composite boards are evaluated properly. The experimental results reveal that both types of PET/CF composite boards possess excellent thermal insulation performance and fire resistance property. Also, for both types of PET/CF composite boards, the average sound absorption coefficient increases with the increased amount of CF.     

Ultra-porous flexible PET/Aerogel blanket for sound absorption and thermal insulation

Ultra porous and flexible PET/Aerogel blankets were prepared at ambient pressure, and their acoustic and thermal insulation properties were characterized. Two methods were selected for the preparation of PET/Aerogel blanket. Method I was a direct gelation of silica on PET. PET non-woven fabric was dipped and swelled in TEOS/ethanol mixture, and pH of reaction media was controlled to 2.5 using HCl to promote hydrolysis. After acid hydrolysis, pH was controlled to 7,8,9, and 10 with NH₄OH for the condensation. Method II was by the dipping of PET non-woven fabric in the dispersion of Silica hydrogel. The gelation process was same with Method I. However, PET fabric was not dipped in reaction media. After the hydrogel was dispersed and aged in EtOH for 24 hrs, then, PET non-woven fabric was dipped in the dispersion of hydrogel/EtOH for 24 hrs. The surface modification was carried out in TMCS/n-hexane solution, then the blanket was washed with nhexane and dried at room temperature to prevent the shrinkage. The silica areogels synthesized in optimum conditions exhibit porous network structure. Silica aerogel of highly homogeneous and smallest spherical particle clusters with pores was prepared by gelation process at pH 7. When direct gelation of silica was performed in PET nonwoven matrix (Method I), silica aerogel clusters were formed efficiently surrounding PET fibers forming network structure. The existence of a great amount of silica aerogel of more homogeneous and smaller size in the cell wall material has positive effect on the sound absorption and thermal insulation.     

Proximate Composition and Functional Properties of Fullfat and Defatted Beniseed (Sesamum Indicum L.) Flour

The proximate composition and functional properties of fullfat and defatted beniseed (Sesamum indicum L.) flour were evaluated. Functional properties studied were foam capacity and stability, water and oil absorption, bulk density, emulsion capacity and nitrogen solubility. Defatting increased the crude protein, ash, crude fiber, carbohydrate and mineral contents. Defatted flour showed comparatively better foam capacity and stability, water absorption and emulsion capacities but diminished bulk density and oil absorption capacity. Nitrogen solubility was pH dependent with a minimum at pH 4 and maximum at pH 8. Maximum nitrogen solubility (95%) was recorded for defatted flour while that for the fullfat flour was 60%. The proximate composition and functional properties of the samples suggest that beniseed flour would have useful application in fabricated foods.     

Transverse impact characterization of carbon woven fabric-foam sandwich composites with carbon nanotubes

Different contents of carbon nanotubes were incorporated in an epoxy matrix that was then reinforced with carbon woven fabric and foam to manufacture the carbon woven fabric-foam sandwich composites. The transverse impact characterizations of the sandwich composites were reported. The split Hopkinson pressure bar apparatus were employed to test the transverse impact behaviors. The impact wave signals were recorded and the impact load versus displacement curves and impact damages of the sandwich composites were observed to analyze the energy absorption and the impact damage mechanisms. It was found that the failure area and energy absorption is increased as the increase of impact velocity and decrease of carbon nanotubes content. The main failure modes are foam breakage and the interface delamination between the woven fabric and foam.     

Studies on compression behaviour of polypropylene needle punched nonwoven fabrics under wet condition

The present study deals with the effect of parallel-laid and cross-laid web of polypropylene needle punched nonwoven fabrics on compression properties (initial thickness, percentage compression, percentage thickness loss and percentage compression resilience) under wet condition. These compression properties of polypropylene needle-punched nonwoven under wet condition have also been compared with its dry condition. With the increase in needling density the initial thickness, percentage compression and percentage thickness loss of the fabrics under wet condition decrease to higher extent compared to its dry condition both in case of parallel-laid and cross-laid fabrics. Cross-laid nonwoven fabric presents lower value of initial thickness percentage compression and thickness loss compared to parallel-laid fabric which is very prominent at high needling density (350 punches/cm²). The percentage compression resilience shows increasing trend with the increase in needling density both under dry and wet conditions of parallel-laid web. It also follows similar trend in case of cross-laid nonwoven under wet condition. The optimum needling density for compression resilience of cross-laid nonwoven fabric under dry condition is 250 punches/cm².     

Preparation and property evaluation of sound-absorbing/thermal-insulating PU composite boards with cushion protection

This study used recycled fibers and inflaming retarding fibers to form composite nonwoven and then compounded with PU foam preparing composite board with sound-absorbing, thermal-insulating and cushion properties. Effects of foam density and composite nonwoven on three properties of PU composite board have studied. Result shows that, with increase of foam density, composite boards had higher sound absorbing coefficient at medium and high frequencies, lower thermal insulation as well as firstly improved and then decreased cushion property. After assessment, the optimal foam density was 60 kg/m³. For diverse requirements, PU foam matches with different kinds of composite nonwoven to achieve excellent cushion property. The resulting composite board can effectively ease hurts from rigid wall, and could be applied in kindergarten, music hall, audio-visual room, pub and recreational centre etc in the future.     

Hemp-fiber based nonwoven composites: Effects of alkalization on sound absorption performance

The effects of the material and treatment parameters on airflow resistivity and normal-incidence sound absorption coefficient of alkalized three layered nonwoven composites have been studied. The material parameters included fiber size and porosity. The treatment factors included the temperature, duration and concentration. The alkalized composite was a three-layered nonwoven sandwich structure consisting layers of Polypropylene/Hemp/Polypropylene. Alkalization treatment has been found to result in a loss of basis weight and a decrease in air flow resistivity. Among treatment factors, only temperature was found to be a statistically-significant factor on air flow resistivity. Higher-temperature alkalization leads to higher air flow resistivity compared to the lower-temperature treatment. Alkalization at higher temperature and higher concentrations gives better results in normalized sound absorption performance compared to lower-temperature and lower-concentration treatments, respectively.     

Morphology and crystal structure on electrospun fibrous poly(1-butene) (PB) membrane

This work was discussed on the morphology and crystal structure on electrospun fibrous PB membrane, namely, both highly porous PB film and the fibrous PB nonwoven prepared by the same method of electrospinning process. Both the tip-to-collector distance (TCD) and the surrounding temperature were crucial parameters for determining the resulting morphologies. In terms of shorter TCD (below 10 cm) and lower surrounding temperature (below 40 °C), highly porous PB film was almost electrospun because such shorter distance and lower temperature were completely not enough to evaporate the used solvents during electrospinning. Fibrous PB nonwoven, however, was obtained at longer TCD and higher temperature (80 °C). X-ray diffraction (XRD) and differential scanning calorimeter (DSC) analyses demonstrated that a porous PB film revealed two crystal structures of dominant form III and small amount of form II arising from the melt recrystallization from form III crystals, while fibrous PB nonwoven showed form I due to the aging time over 2 weeks at room temperature after electrospinning. As a result, it was found that PB membrane can exhibits a porous film and fibrous nonwoven with different morphologies and crystalline microstructures depending on TDC and surrounding temperature although they were prepared from the same method of electrospinning.     

Preparation and Mechanical Property Evaluations of Puncture-Resistant Insoles Composites Reinforced by High-Modulus Filament and Thermal Bonding

High-modulus PET filaments and thermal bonding are used to reinforce the puncture resistance stability of the insole composite. This study aims to discuss the influences of the amount of low-melting-point polyester fibers (LMPET) and needle densities (ND) on tensile, bursting, and quasi-static puncture resistance properties. Besides, significance of LMPET amount and ND on puncture resistance against flat-head (A), spherical-head (B), and pointed-head (C) probes are in particular investigated to simulate the diversified application environments for insoles. Research result shows that, LMPET amount significantly affects the static puncture resistance against three probes; ND only significantly influences the puncture resistance against Probe A and C. Thermal bonding significantly improves the puncture strength against Probe B with various LMPET amounts of insoles, but evidently increases the puncture resistance against Probe A and C when being punched at various ND. The amount of LMPET fibers has a positive influence on the puncture strength of insoles, and 70 wt% of LMPET provide the average static puncture resistance up to 342.6 N. The high-modulus resultant insoles have advantages of flexibility, ease of process, and bendability with a higher and more stabilized puncture resistances.     

The modelling of porous properties regarding PES/CV-blended nonwoven wipes

This paper reports the results from the modelling of porous properties of raw polyester/viscose nonwoven wipes. This was carried out on the basis of nonwoven construction parameters (fibre fineness, web mass per unit area, web thickness), mercury intrusion porosimetry, and a non-deterministic modelling method, e.g. genetic algorithms. Despite the fact that the nonwoven fibre webs had different porous structures as a result of varying their construction parameters, it was possible to very precisely develop predictive models of the porous parameters (pore volume, volume porosity, pore surface area, pore diameter). The results show that the genetic algorithm is a successful modelling tool in those cases where the testing population is limited but still different. The proposed models provide guidelines for the engineering of nonwoven wipes in order to fit the desired porosity properties.     

Development of Multilayered Nanocomposites for Applications in Personal Protection

The aim of the presented research was to study the influence of surface layer material on improvement of impact, dielectric, EMI shielding and sound absorption properties of sandwich composites. The sandwich composite structure consisted of Kevlar or Carbon woven fabric at the surface layer, recycled high loft nonwoven in the center and a mixture of carbon particles/epoxy matrix as a binder to hold the surface layer and core together. The carbon particles were incorporated in epoxy in order to improve failure mechanism and enhance dielectric properties or electromagnetic shielding of sandwich composites. The biggest improvements on impact properties of sandwich composites were obtained when Kevlar fabric was used as surface layer. However, surface layer of carbon fabric was found to provide better dielectric properties and improve EMI shielding of sandwich composites against Kevlar fabric surface layer.     

A study on heat insulation of composites made of recycled far-infrared fibers and three-dimensional crimped hollow polyester fibers

Far-infrared polyethylene terephthalate (FPET) fibers have been commonly used in clothing in order to attain heat retention, and the combination of three-dimensional crimped hollow polyethylene terephthalate (TPET) fibers makes the clothing to be fluffy and air permeable, and thereby improves the wearing comfort. This study aims to make thermally insulating nonwoven composites by using recycled far infrared fibers. The composites are used to cover the heat transfer lines and prevent the heat emissivity. A specified amount of low-melting-point polyethylene terephthalate (LPET) fibers and FPET and TPET fibers at different ratios are blended, followed by being needle punched at 100-300 needles/min, and then hot pressed at 120 °C, in order to form thirty nonwoven composite types. These nonwoven composites are measured for their porosity, thickness, and air permeability, and are tested for thermal insulation and temperature-rise slope under a constant ambient temperature.     

Aerogel based nanoporous fibrous materials for thermal insulation

In this research work, the thermo physiological properties of polyester/polyethylene nonwoven composite wraps of varying thicknesses impregnated with aerogel were studied and compared. The SEM images were also taken to compare the physical configuaration of the aerogel based fibrous composites. Specific thermal properties like thermal conductivity, thermal resistance, thermal diffusivity and thermal absorptivity were measured using alambeta instrument. The air permeability of the thermal wraps was measured in air permeability tester. The relative water vapor permeability and absolute water vapor permeability was measured in Permetest. These tests were conducted to understand thermal properties, air and water vapor permeability of flexible aerogel based composites with nanoporous structure. The results of the experiments were statistically analyzed and found to be within confidence intervals.