Short Aramid Fibers Research Articles

Tribological properties of graphene oxide reinforced aramid paper-based composites

Self-lubricating paper-based composites can provide technological solutions such as low friction and extended service life for the aerospace airframe kinematic mechanical components. To improve the tribological properties of aramid short fibers, this study chemically combined graphene oxide (GO) with aramid nanofibers (ANF) through intermolecular forces, creating a self-lubricating GO-reinforced aramid paper-based composite GO/ANF. Mechanical performance tests have shown that the introduction of GO can significantly improve the fracture strength, Young's modulus, and toughness of paper-based composites. The frictional performance test results show that compared with ANF, the GO/ANF paper-based composites can maintain the lowest coefficient of friction (COF) and wear under high load and high sliding rate conditions. When the amount of GO added is 1 wt%, the COF and volume wear rate of GO/ANF paper-based composites are reduced by 23 % and 89 %, respectively. Mechanism analysis indicates that synergistic effects and friction transfer films are important factors contributing to the excellent performance of paper-based composites. This GO/ANF paper-based composite has good application prospects as a good anti-wear liner material in self-lubricating sliding bearing.

Constructing flexible fiber bridging claws of micro/nano short aramid fiber at interlayer of basalt fiber reinforced polymer for improving compressive strength with and without impact

The high-performance Basalt Fiber Reinforced Polymer (BFRP) composites have been prepared by guiding Micro/Nano Short Aramid Fiber (MNSAF) into the interlayer to improve the resin-rich region and the interfacial transition region, and the flexible fiber bridging claws of MNSAF were constructed to grasp the adjacent layers for stronger interlaminar bond. The low-velocity impact results show that the MNSAF could improve the impact resistance of BFRP composites. The compression test results demonstrate that the compressive strength and the residual compressive strength after impact of MNSAF-reinforced BFRP composites were greater than those of unreinforced one, exhibiting the greatest 56.2% and 73.3% increments respectively for BFRP composites improved by 4wt% MNSAF. X-ray micro-computed tomography scanning results indicate that the “fiber bridging claws” contributed to better mechanical interlocking to inhibit the crack generation and propagation under impact and compression load, and the original delamination-dominated failure of unreinforced BFRP composites was altered into shear-dominated failure of MNSAF-reinforced BFRP composites. Overall, the MNSAF interleaving might be an effective method in manufacturing high-performance laminated fiber in industrial production.

High‐strength, recyclable and healable polyurea/aramid fiber elastomeric composites

AbstractThe demanding and rigorous modern work environments present significant challenges to the protective capabilities of engineering materials. Polyurea elastomers often face limitations in terms of inadequate strength and a lack of weather resistance, however, polyurea composites holds great promise in addressing these issues. This study prepared modified ultrafine aramid short fibers using a mechanochemical method. Subsequently, in‐situ polymerization was utilized to combine the modified ultrafine aramid short fibers (M‐AF) with polyurea, resulting in the synthesis of a composite material characterized by recyclability, robust weather resistance, and favorable mechanical properties. Subsequently, intensive researches were conducted on the mechanical properties, recyclability, self‐healing performance, weather resistance, and chemical medium resistance of the composites. The composite at 0.1 wt% of M‐AF exhibited improvements in tensile strength (27.2 ± 0.8 MPa) as well as obviously enhanced impact performance (428.8 ± 6 kJ/m2), and recovered most of its mechanical properties after recycling and self‐healing. Moreover, the composite exhibits excellent weather resistance and chemical resistance, enabling it to uphold its exceptional protective performance even in the face of challenging environments.Highlights Ultrafine aramid fibers were prepared using a simple mechanochemical method. Mechanochemical methods were employed to surface modify aramid fibers. The composites have good strength, recyclability, weather resistance.

Numerical and experimental investigation for flexural response of Kevlar short fiber tissue/carbon fiber belts toughened honeycomb sandwich plate

This paper investigates the flexural behavior of honeycomb sandwich panels with a toughened/untoughened interface using carbon fiber belt and short aramid fiber tissues. In the first part of the paper, bending response analysis of carbon fiber aluminum honeycomb sandwich plates with an untoughened interface is done using finite element-based first-order shear deformation theory. In the second part, experimental analysis is done to examine the effect of loading rates on the mechanical characteristics of plain and toughened sandwich panels using a three-point bending test. Four types of interface toughening are used as unidirectional and bi-directional stitches of carbon fiber belts, Kevlar short-fiber tissues, and carbon fiber belts combined with Kevlar short-fiber tissues. Experimental result shows that interface toughening improves the maximum load and energy absorbed by sandwich specimens for all loading rates. A scanning electron microscope is used to observe and analyze the failure mode and mechanism of strengthening the interface. It is observed that the stitch of the carbon fiber belt increases the adhesion contact between face sheets and core leading to prevent interfacial debonding. The peak load and energy absorptions of carbon fiber belts toughened interface sandwich are increased by 51 % and 42.5 %, respectively, compared with that of the plain sandwich by a small increment of weight (14%).

Interfacial toughening and bending performance of the CFRP/aluminum-honeycomb sandwich

CFRP / honeycomb sandwiches often fail prematurely due to interface debonding when subjected to bending loads. In this paper, three kinds of toughening interfaces were designed, and their effects on the sandwich’s three-point bending performances (including peak force and energy absorption) were studied. The results showed that the peak force and energy absorption of the sandwich were increased by 43.6% and 141.3%, respectively by adding a multi-scale toughening film (short aramid fiber (AF) film grafted with polydopamine (PDA) and graphene oxide (GO)) at the interface. The toughening interface affected the deformation process and failure mode of the sandwich by changing the competition mechanism between the facesheet, interface, and honeycomb strength. The short fibers of toughening film formed bridges at the toughened interface, and the crack propagation mechanism changed from interface debonding to a combination of interface debonding and matrix fracture. In addition, the test results revealed that the wettability, tensile strength, surface roughness, and specific surface area of the fiber could be significantly improved by treating with PDA and GO, which lead to crack deflection at the interface. Thus, the interface debonding is effectively delayed or prevented.

Interlaminar fracture toughness of carbon/epoxy composites laminates toughened by short carbon fiber

AbstractIn this paper, short carbon fiber (SCF) interlaminar toughened carbon fiber reinforced epoxy resin (CF/EP) composite laminates were prepared. The effect of SCF content on the mode II interlaminar fracture toughness (GIIC) and flexural properties of CF/EP composites was investigated. It was shown that the addition of SCF between the plies had an effect on the GIIC of the composites. When the SCF content was 10 g/m2, the GIIC increased from 1506.62 J/m2 to 1995.6 J/m2, which improved by about 32.46%. When the content of SCF was 5 g/m2, the flexural strength and flexural modulus increased by 36.92% and 98.48%, respectively, showing the best performance. The toughening mechanism of SCF was observed by SEM images as SCF debonding and pulling out from the resin and SCF fracture. The present study was also compared with our previous study on short aramid fiber interlaminar toughened CF/EP composites, and the test data and SEM images of the two experiments were compared to analyze the effect of different short fibers on the interlaminar toughening effect, which provides some reference for the selection of interlaminar toughening materials.

Comparative evaluation of mechanical properties of short aramid fiber on thermoplastic polymers

Abstract This study investigated the mechanical performance of short aramid fiber on polypropylene, polyethylene, polyamide 6, and polyamide 12. Extrusion, press molding, and CNC cutting methods were used in the production of composite samples. Tensile, three-point bending, drop weight and hardness tests of the composites were carried out. As the fiber volume fractions increased, the mechanical properties of the composites improved, but the most efficient fiber fractions for each matrix changed. To analyze the performance of the fibers in the matrix on the composites, scanning electron microscope (SEM) images of the fractured surfaces as a result of tensile and drop weight tests were examined. As the fiber volume fractions increased, the fiber deformation increased, and as a result, the mechanical performance of the composites was adversely affected. Analysis of variance (ANOVA) and F test were performed using signal/noise values to analyze in detail the effect of experimental parameters on output values. Finally, the results of a regression equation model were compared with the experimental readings. It was found to be in good agreement with the model and the results of the experiment.

Short aramid fiber reinforced thermotropic liquid crystalline polyester composites: Fabrication, thermal, and mechanical properties

We conducted a study to analyze the impact of short aramid fibers (AFs) on the melt-rheological behavior, thermal transition, thermal stability, and mechanical durability of thermotropic liquid crystal polyesters (TLCPs). By using different AF loading contents ranging from 3–15 wt%, we produced TLCP matrix composites through masterbatch-based melt-compounding and injection-molding. The SEM images and FT-IR spectra demonstrate that the AFs are dispersed in the TLCP matrix with a microfibrillar structure through good interfacial adhesion caused by specific intermolecular interactions between the TLCP and AFs. As a result, the complex viscosity, shear storage/loss moduli, and thermal transition (melt-crystallization, glass transition, and melting) temperatures of the composites increase with increasing AF filler content. However, the melt-crystallization and melting enthalpies increase only at low AF loading contents of 3–5 wt%. At high AF contents of 7–15wt%, the enthalpies decrease owing to the partial aggregation of AF fillers. The thermogravimetric analysis proves that the thermal stability of TLCP/AF composites improves when the AF filler is introduced. The dynamic mechanical analysis using the stepped isothermal method shows that the addition of 5 wt% AF to the TLCP leads to an approximately 150% improvement in elastic moduli and long-term mechanical durability at elevated temperatures.

Strain softening of natural rubber composites filled with carbon black and aramid fiber

Engineered rubber vulcanizates may contain a low content of short fibers and a high content of nanoparticles while the effects of the different fillers on the softening behavior are not yet explored. Herein, influences of carbon black (CB) and short aramid fiber (AF) on the Payne and Mullins effects of natural rubber composites are investigated for the first time by creating master curves of dynamic modulus or dissipation energy with respect to the straining responses of the matrix. It is revealed that the composite vulcanizates demonstrate the Payne effect characterized by decay of storage modulus, weak overshoot of loss modulus, and very weak high-order harmonics; this effect is mainly dominated by the rubber matrix experiencing microscopic strain amplitude enlarged by the filler. The composite vulcanizates exhibit the Mullins effect that becomes increasingly marked with increasing filler loading and is partially recovered by thermal annealing at relatively high temperatures. The energy dissipation during cyclic tensions is rooted in the viscoelastic deformation of the matrix and the filler-rubber interfacial debonding. The former is marked at room temperature where the rubber phase undergoes a crystallization-melting process during loading-unloading. The latter being marked in the presence of a small content of AF causes yieldinglike deformation for the virgin composites at low tensile strains, and its contribution to the softening is not recoverable during thermal annealing. The results show that the viscoelastic matrix is of importance in controlling the softening of the composite vulcanizates, which will be of guiding significance to conduct research studies on high-performance rubber composites products.

Simultaneously improve the mode II interlaminar fracture toughness, flexural properties, and impact strength of CFRP composites with short aramid fiber interlaminar toughening

AbstractThis work mainly focuses on the mode II interlaminar fracture behavior of carbon fiber composite that was interlaminar toughened by short aramid fiber modified epoxy resin. The short fibers were first dispersed in the epoxy matrix and then in the laminate interlayer area during the lamination process. The ENF test evaluated the Mode II interlaminar fracture toughness of laminates. The results show that mode II interlaminar fracture toughness increases with the addition of short fibers. When the fiber content is 10 g/m2, the toughening effect is the best at 2437.72 J/m2, which is about 61.8% higher than the untoughened sample. The toughening mechanism of CFRP laminates by adding short fibers was observed by mode II fracture surface SEM images. In addition, flexural properties and Charpy impact properties of short fiber modified resin interlayer toughened laminates were also studied. The results showed that with this method, flexural properties and impact strength were improved to a certain extent, proving that this method is an effective interlaminar toughening method.

Three-dimensional phase field modeling of progressive failure in aramid short fiber reinforced paper

As a kind of synthetic aromatic polyamide, aramid fiber has many outstanding properties, such as high strength, high modulus, etc. The composited paper reinforced by aramid fiber is widely used in honeycombs and its strength is of great concerns. In this paper, a three-dimensional progressive failure phase field model is employed to investigate the failure mechanism of aramid honeycomb paper under microscopic length scale. A mesh mapping technique is used to handle the complex geometry of the material, and an explicit solving scheme is used to improve the solving efficiency. The theory is implemented into ABAQUS through the users’ subroutine VUEL. The interfacial debounding and matrix cracking in the short fiber reinforced composite are captured successfully, and the complicated failure mechanism is explored from the modeling results. The present phase field modeling technique has provided a useful numerical tool for the strength prediction of aramid short fiber reinforced composites.

Suppression of Brake Noise and Vibration Using Aramid and Zylon Fibers: Experimental and Numerical Study.

Aramid pulp/fiber is the most vital ingredient of brake friction material (FM) formulation. It is perpetually added to achieve quality brake pads/shoes and improve the overall friction and wear performance. Additionally, novel Zylon fibers have a superior property to aramid fibers. However, no studies give insights on their influence on brake noise and vibration (NV) performance. In the current work, a series of six different types of eco-friendly brake pads was developed. The first five contain aramid pulp, aramid short fibers, and Zylon fibers of different sizes (1, 3, and 6 mm) as the theme ingredients (3 wt %) by keeping the parent composition identical. Additionally, one more pad was developed that contains no aramid/Zylon fibers (i.e., reference pad). The pads were characterized for physical and mechanical properties. The damping and natural frequencies of pads were measured experimentally and numerically. All brake pads were evaluated for detailed NV performance by following the SAE J 2521 test schedule. In addition, numerical simulation was performed to validate the experimental brake squeal results. Results revealed that aramid/Zylon fiber-based pads improved the porosity, damping, and compressibility. Overall, brake noise and vibrations were improved for aramid/Zylon fiber-based pads by 1.2–1.5 dBA and 20–25%, respectively, compared to the reference pad. The complex eigenvalue analysis (CEA) proved that squeal was mainly influenced by the damping and density of the pad materials. Thus, aramid/Zylon fiber-based pads can effectively suppress the instability of the brake system and reduce the brake squeal propensity.

Study on aramid short fiber reinforced CFRP/aluminum layered structure and its galvanic corrosion resistance

In order to strengthen the bonding interface and weaken the influence of galvanic corrosion on carbon fiber/aluminum laminated composite, the aramid fiber with resin was introduced into the bonding layer of carbon fiber aluminum laminated composite structure to composite in this study. The ultimate load of carbon fiber/aluminum laminated composite reinforced by aramid fiber was studied based on the End Notched Flexure (ENF) three-point bending test and the fracture surface was analyzed and compared by Scanning Electron Microscopy (SEM) observations. Compared with the pure resin adhesive, the bearing capacity of Carbon Fiber Reinforced Polymer (CFRP)/aluminum composite structure reinforced by thin film prepared by 1 mm aramid short fiber can be increased by 9.7%. After the accelerated corrosion test, the bearing capacity of 1 mm aramid fiber film has been reduced by only 8.40% compared with the structure without corrosion treatment. However, compared with the CFRP/aluminum composite structure with pure resin adhesive layer, the ultimate bearing capacity of the specimen with aramid fiber reinforced adhesive layer is still 28.69% higher after immersion in salt solution corrosion environment. The aramid fiber reinforced carbon fiber/aluminum galvanic corrosion protection mechanism of the layered composite structure was discussed with detailed Scanning Electron Microscopy (SEM) observations and the Energy Dispersive Spectroscopy (EDS) spectrum analysis of corrosion product elements.

Mechanical and tribological behaviour of PA6 and short aramid fiber composites

This paper presents the results of mechanical and tribological characteristics for two composites: PA6 as matrix and 5% aramid whiskers as additive material and PA6 + 10% aramid whiskers, comparing them to those made of PA6 (polyamide 6). To improve the mechanical and thermal properties of polyamide (PA6), the composites were prepared via the Brabender lab mixer and mould forming under given pressure and temperature conditions. Test specimens made of pure PA6 and PA6 mixed with 5 wt.% and 10 wt.% aramid whiskers were subjected to mechanical tests (three-point bending and impact), thermo–mechanical test (HDT - heat deflection temperature), tribological test (block-on-ring) and analyzed from morpho-structural point of view. Compared to the PA6 samples, the mass concentrations of aramid whiskers improved the HDT deflection temperature values. In the case of samples with 5% aramid whiskers, the absorbed energy increased by 13% and for those with 10% aramid whiskers they increased by 30%. Aramid whiskers-doped materials performed much better on severe tribological testing as compared to PA6 samples. Increasing the deflection temperature, also improved their resistance from a tribological point of view.

Exploration of Zylon fibers with various aspect ratios to enhance the performance of eco-friendly brake-pads

This study explores the potential of high-performance Zylon fibers (ZF) for the first time in brake-pads. It also reports on the influence of the aspect ratio of these fibers on the performance properties of the eco-friendly brake-pads first time, enabling the right selection of the fiber length for the best performance. In addition, Aramid short fibers (AF) and pulp (AP) were also selected as theme ingredients, which would-be competitors to the Zylon fibers (ZF) in brake-pads. A series of six types of brake-pads was developed (theme ingredients- 5 vol%) by keeping parent ingredients fixed. A comparative performance assessment for different properties was carried out. Tribological studies on a full-scale brake dynamometer showed that almost all performance properties such as resistance to wear and fade (pressure, speed, and temperature) improved due to Zylon fibers. The average coefficient of friction slightly decreased for ZF-based pads compared to Aramid pads. Overall, ZF with 3 mm length proved the best one based on the multiple objective optimization by ratio analysis (MOORA) method. Worn surfaces of pads were analyzed using scanning electron microscopy (SEM).

Experimental and numerical investigation of low velocity impact on hybrid short-fiber reinforced foam core sandwich panel

This paper presents an experimental and numerical study of the low-velocity impact on foam core sandwich panels reinforced using hybrid short fibers. The foam cores were reinforced with carbon, aramid and carbon-aramid hybrid short fibers. The face-sheets were made of two layers of glass/epoxy, and foam cores were made of two-part polyurethane. In order to acquire the appropriate weight ratio between foam and short fibers, the weight percentage of 10% was chosen for short fibers. Comparing the experimental results proved that carbon, aramid, and carbon-aramid respectively had a better effect on increasing Young modulus by around 100 to 180 per cent. Before performing impact tests, indentation tests were conducted and based on the results for the parameter of impact energy, the value of 6 J was chosen. According to the results of impact tests and the maximum contact force, hybrid reinforced foam, aramid short fiber reinforced foam and carbon short fiber reinforced foam improved the properties respectively by 18 to 30 per cent in comparison to non-reinforced foam. Furthermore, numerical simulations were conducted via ABAQUS. After modeling face-sheet and foam separately, and verifying the results with experiments, the sandwich panel was modeled entirely while the simulation difference of 9.1% on average with the experiment results was concluded.

Compression‐after‐impact properties of carbon fiber composites with interlays of Aramid pulp micro‐/nanofibers

AbstractThe inherent resin‐rich ply interfaces in laminar carbon fiber reinforced polymer (CFRP) composites are toughened by ultrathin interlays formed by Aramid pulp (AP) micro‐/nanofibers, to show that stronger and more impact‐resistant CFRP can be manufactured with minimum disruption to the current composite forming process. Flexible nonwoven AP micro‐/nano‐fibers, less than 1 mm in length, can conveniently fit in the uneven surface profiles or microresin‐rich areas between carbon fiber plies and form in situ quasi‐Z‐directional fiber‐bridging across the ply interfaces. CFRPs with multiple interfacial AP interlays estimated to be around 3 and 6 g/m2 were tested before and after low energy impact. Ultrathin resin‐rich ply‐interface layers in plain CFRP were transformed into ultrathin “Short Aramid Fiber Epoxy” layers by the AP interlays (20–50 μm in thickness), leading to enhanced compressive energy absorption and up to 86.7% increase in Compression‐After‐Impact Strength. Keeping the interlay thin (around 30 μm or thinner if possible), even the compressive strength (without impact) is not compromised, and the energy absorption under compressive loading (without impact) is 130% higher. The distinctly different compressive failure mechanisms, delamination failure of the plain CFRP was transformed into matrix shear failure in AP‐toughened CFRP, as identified by nondestructive X‐ray microcomputed tomography scans. Scanning electron microscopy was performed on the failure surface to inspect the microscopic toughening mechanisms.

Interlaminar mechanical properties of nano- and short-aramid fiber reinforced glass fiber-aluminum laminates: a comparative study

Delamination damages limit the application potential of Fiber metal laminates, hence improving the interlaminar mechanical properties has always been a research focus and challenge in this field. The toughening effect of two fillers, i.e., nano-aramid fibers (ANFs) and short-aramid fibers (ASFs), which are used at the interface of glass fiber-aluminum laminates, have been investigated. Chemical pretreatments of aluminum alloy surface were conducted to ensure the better adherence between the fiber composites and metal sheets. Results revealed that Mode-I and Mode-II fracture toughness of the laminates could be simultaneously improved when using the two fillers at the interface of glass fiber-aluminum laminates. Attributed to the better dispersion of ANFs in epoxy matrix, the toughening performance of ANFs is better than that of ASFs in this case. The mechanism of interlaminar toughening was revealed with electron microscopic observation of fracture morphology. Meanwhile, the finite element analysis based on bilinear cohesive zone model was adopted to predict the increased interlaminar tensile and shear strength.

Improved mechanical performances of short aramid fiber‐reinforced polypropylene composites by Ti3C2 Mxene nanosheets

AbstractFiber‐reinforced polypropylene (PP) composites are widely used for structural bearing because of their excellent mechanical property. So, it is necessary to improve the mechanical property of fiber‐reinforced PP composites. In this present, two‐dimensional Ti3C2 Mxene nanosheets were bound to short aramid fiber (SAF), forming Ti3C2 nanosheets‐modified SAF (Ti3C2/SAF), aiming to improve PP mechanical property. The Ti3C2 nanosheets were obtained after hydrofluoric acid etching and ultrasonically delamination procedure, followed by chemically bound to the surface of H3PO4 solution‐treated SAF to form Ti3C2/SAF. The Ti3C2/SAF‐reinforced PP (Ti3C2/SAF/PP) composites were prepared by a melt blending method. Scanning electron microscopy images showed that the Ti3C2/SAF modified with different concentration of Ti3C2 nanosheets solution presented the distinct morphologies, with the 0.3 mg/ml Ti3C2/SAF formed a relatively uniform Ti3C2 nanosheets coating on the SAF surface. Test results of mechanical performance indicated that the tensile and impact strength of Ti3C2/SAF/PP composites were significantly improved. Especially, the maximum tensile and impact strength of 0.3 Ti3C2/SAF/PP composite at 5 wt% reached to 37.8 MPa and 14.0 kJ/m2, which was increased by 11.5% (or 28.1%) in tensile strength and 12.9% (or 38.6%) in impact strength, compared with that of SAF/PP composite (or PP matrix). This can be attributed that Ti3C2 nanosheets binding to SAF improved the interfacial bonding strength between SAF and PP. This work provides a promising strategy for improving the mechanical properties of fiber‐reinforced PP composites.

Three-point bending properties of carbon fiber/honeycomb sandwich panels with short-fiber tissue and carbon-fiber belt interfacial toughening at different loading rate

The bending performances at different loading rate are studied for carbon fiber/honeycomb sandwich panels toughened by short aramid fiber tissues and carbon fiber belts. The carbon fiber belts are stitched cross the pores of honeycomb core for interfacial improvements. Three-point bending tests at different loading rates are carried out to investigate the effect of short aramid fiber tissue and carbon fiber belt on mechanical properties of carbon fiber/honeycomb sandwich specimens. Experimental results firstly indicate that the short-aramid-fiber interfacial toughening and carbon fiber belts toughening could both enhance the energy absorption and peak load of sandwich specimens at loading rates ranging from 2 mm/min to 500 mm/min. The failure modes and microstructures of toughened specimens are observed to analyse and explain the underlying mechanism of enhancing effect. It is illustrated that crack isolation phenomenon is found to be the main mechanism for avoiding interfacial damage of the sandwich specimen.