Nylon Matrix Research Articles

Mechanical characterization of additive manufacturing composite parts

Additive Manufacturing is a novel manufacturing method in which the part is produced layer by layer from a 3D CAD model. In this work, we present the mechanical characterization of Fusion Deposition Modeling (FDM). Composite parts made by a nylon matrix with two kinds of fiber reinforcements: carbon fiber or fiberglass. From the obtained microstructure, we perform a division of the composite part in regions, and individual stiffness matrices are encountered by either using a linear elastic isotropic model, for the case of solid matrix filling, or an orthotropic linear elastic model based on micromechanical results. Then, a volume average stiffness method is employed to perform the characterization of the whole part. The theoretical results are compared with the experimental data, showing good agreement for both cases. This research allows the prediction of the structural behavior of additive manufacturing 2composite parts.

Colossal dielectric permittivity of Nylon-6 matrix-based composites with nano-TiO2 fillers

Herein, the nanocomposite films of Nylon-6 with reinforced nano-TiO2 were explored for their charge storage capacity. The high dielectric constant (e) of TiO2, along with its compatibility with Nylon-6, formed the basis for the present study. TiO2 nanoparticles were synthesized initially using hydrothermal technique. The microscopic uniformity and anatase-phase purity of the TiO2 nanoparticles were confirmed with the help of morphological and structural investigations. The effect of weight fraction of TiO2 in Nylon-6 was investigated to understand the robustness of the fabricated nanocomposites. The composite films with 5, 10 and 20 wt% of TiO2 in Nylon-6 matrix were prepared, and their dielectric behavior was explored by fabricating capacitors with parallel plate architecture. The composite film with 20 wt% TiO2 showed the highest dielectric parameters. The nanocomposite films have the exceptional dielectric quality with e ~ 124 and low dielectric loss of 0.51 at 1 kHz. The colossal dielectric nature along with minimum sophistication in the film fabrication process makes the present nanocomposite to be a potential candidate for the various electronic devices.

Out-of-Plane Compressive Response of Additively Manufactured Cross-Ply Composites

ABSTRACTDigital manufacturing was employed to 3D print continuous Carbon, Glass and Kevlar fibre reinforced composites in Unidirectional (UD) [0°], Off-axis ±45° and Cross-ply [0°/90°] layup sequence. These 3D printed composites were subjected to quasi-static, in-plane tension and out-of-plane (compression and shear) loading. The tensile strength of 3D printed Carbon, Glass and Kevlar UD laminates was significantly lower than that of 3D printing filaments used to manufacture them. The type of fibre (brittle/ductile) reinforcement was found to be governing the shear yield strength of 3D printed composites despite having the same Nylon matrix in all the composites. Out-of-plane compressive strength of the 3D printed Carbon and Glass fibre reinforced composites was independent of specimen size. Contrary to that, Kevlar fibre composites showed a pronounced size effect upon their out-of-plane compressive strength. A combination of X-ray tomography and pressure film measurements revealed that the fibres in 3D printed composites failed by ‘indirect tension’ mechanism which governed their out-of-plane compressive strength. To gain further insights on the experimental observations, Finite Element (FE) simulations were carried out using a pressure-dependent crystal plasticity framework, in conjunction with an analytical model based on shear-lag approach. Both FE and analytical model accurately predicted the out-of-plane compressive strength of all (Carbon, Glass and Kevlar fibre reinforced) 3D printed composites.

On wear of 3D printed Al2O3 reinforced Nylon6 matrix based functional prototypes

The use of fused deposition modelling (FDM) based functional prototypes for wear resistance applications is presently limited mainly because of selective material availability of filament materials. Various research groups have reinforced several fillers in thermoplastic base to prepare feedstock filaments to improve the mechanical properties and to address the reusability issue of polymeric waste. But hitherto the effect of Al2O3 particle sizes (as single, dual and triple particle size as reinforcement) in Nylon6 thermoplastic blend has been less explored. In the present investigation an effort has been made to prepare feed stock filament for 3D printing application to explore its wear resistant properties. The current investigation suggested that dual particle size reinforced pin exhibit better wear properties followed by triple and single particle reinforced pins. The wear tracks obtained in this study shows that dual particle size based composite material is highly wear resistant as compared to virgin acrylonitrile butadiene styrene (ABS)/ Nylon6. The results have been supported by scanning electron microscopy (SEM) images of prepared pins for wear testing.

Linear Sulfur–Nylon Composites: Structure, Morphology, and Antibacterial Activity

Stabilization of sulfur in its linear form is highly challenging but recently developed inverse vulcanization method succeeded by reacting polysulfur terminals groups with organic cross-linkers. In present work, linear sulfur chains were stabilized in nylon matrix by forming amine-polysulfur complex. Composites were prepared by coextruding nylon with various amount of sulfur (2.5 to 30 wt %) under inert gas environment. Polysulfur chains produced under extrusion condition reacts with terminal amine groups of nylon in molten state and form polysulfur-amine complex. The color of these composites change from translucent to dark brown; which is due to formation of sulfur-amide complex based on FTIR spectroscopy. Furthermore the presence of NH3+ and sulfur anion peaks in XPS spectra confirms the formation of this complex. Disappearance of sulfur crystalline peak and absence of sulfur melt transition in XRD and DSC respectively suggests the conversion of crystalline sulfur into randomly arranged amorphous polys...

Influence of microstructure of carbon fibre reinforced polymer on the metal in contact

The influence of the microstructure of carbon fibre reinforced polymers (CFRPs) with epoxy matrix (E-CFRP) and nylon matrix (T-CFRP) on the galvanic behaviour of DP590 steel, 6022-aluminium alloy, 1040-steel and AZ31-magnesium alloy was investigated in the GMW14872 solution. The E-CFRP/metal couples were initially more galvanic corrosion resistant, but their galvanic corrosion gradually became more severe than the T-CFRP/metal couples. The effective micro-defects in the surface polymer layer of the CFRP samples critically determined the galvanic corrosion. A detailed surface layer model was proposed, the electrochemical processes through the surface polymer layers during galvanic corrosion were discussed. A better understanding on the microstructure of CFRP determined by composites manufacture process can be obtained.

Interlaminar tensile strength for composite materials made by additive manufacturing

The low interlaminar tensile strength of fiber reinforced composite materials presents serious challenges in the design of structures with a considerable radius of curvature, which is commonly found in a wide range of fields such as aeronautics, civil engineering, maritime industry, energy industry, among others. The objective of the present research was to analyze the interlaminar tensile strength, in the interlaminar layer of a material composed of fiberglass as reinforcement in nylon matrix, using a curved beam elaborated by additive manufacturing. To achieve this, tests were carried out according to ASTM Standard, and to determine which parameters significantly influence the failure of the composite material, variations were made in the thickness of the test specimens, which were manufactured following the criteria of the standard. The results obtained allow the assessment of interlaminar tensile strength and specimen behavior after failure.

Tensile mechanical properties of composite materials with continuous fiber produced by additive manufacturing

Additive manufacturing of composites parts reinforced with continuous fibers is emerging as a versatile process, capable of producing complex computer-aided design models by fabricating parts adding material layer by layer. Fused deposition modelling using polymeric materials has been used to produce prototypes, with the constraint of the strength of the material. Recently, the use of continuous fiber reinforcement has provided an alternative for the production of load-bearing functional parts. Current international standards for the characterization of composite materials from mechanical tests are established for parts manufactured by conventional methods, such as, manual molding, injection or coatings. Moreover, the standards do not specify procedures for composite materials produced by additive manufacturing. The objective of this work is to evaluate the performance of the reinforced composite materials produced by additive manufacturing for tensile tests under ISO and ASTM standards, and compare the results in terms of the topology of the material configuration. Average values of the tensile strength for composite materials having a triangular nylon matrix reinforced with fiberglass were obtained within the range of 205 MPa to 234 MPa, with deformations no greater than 0.020 mm. These values are higher than the strength provided by additive manufacturing using materials such as polylactic acid and acrylonitrile butadiene styrene.

Static and fatigue behaviour of continuous fibre reinforced thermoplastic composites manufactured by fused deposition modelling technique

In additive manufacturing (AM), the thermoplastic parts made by FDM present lack of strength and low stiffness, as required for fully functional and load-bearing parts. Due to this restriction, a new technology to reinforce with fibres the thermoplastic filaments was developed over the last years. Continuous fibre reinforced thermoplastic composites (CFRTPC) printers are elevating this technology to a whole new level in terms of efficient production and mechanical properties. Static mechanical properties, as well as fatigue behaviour, were studied since in these types of loads a wide range of engineering dynamic applications can be envisaged. Tensile tests were performed to characterise the static mechanical properties. Fatigue tests were done to analyse the durability behaviour of the FDM composite materials, and the fracture surface was analysed by SEM microscopy. The results showed that carbon fibre isotropic layers had the higher ultimate tensile stress, with 165 MPa. From fatigue tests, stress vs. number of cycles curves (S vs Nf) in the temporary life zone were obtained. It was observed from the results that specimens with nylon matrix, triangular filling pattern and matrix density of 20%, reinforced with carbon fibre at 0-degrees, showed better fatigue performance, increasing significantly the number of cycles before specimen rupture. The parameters for the Basquin’s equation were found (S=A·Nfb), with A = 206 MPa, and b = −0,039. Accordingly, mechanical characterization of continuous fibre reinforced thermoplastic composites was investigated, which showed the potential use as a composite material for engineering applications.

Photoprintable nanowire–polymer blends synthesized by dynamic emulsion polycondensation

ABSTRACTIn this article, we report a photoprintable nanocomposite synthesized at room temperature in less than 10 s by aggressive mixing of two monomer solutions. Polycondensation occurs in the dispersed phase of the dynamic emulsion, microdroplets, in which the nanofillers are suspended. Hence, the synthesized composite microparticles have a high dispersion and high loading of nanofillers. Specifically, silver nanowire (AgNW)–nylon 66 blends with various Ag weight fractions are synthesized and studied. The poly(vinyl pyrrolidone) (PVP)‐functionalized AgNWs (by polyol synthesis) are singly dispersed and tethered to the nylon matrix by PVP with a slight depression of the glass‐transition temperature. The Ag–nylon powder melts under low‐intensity visible continuous wave laser radiation; this allows convenient photoprinting of the nanocomposite structures. Photoprinting is demonstrated at a radiation intensity of 0.3 kW/cm2 (405 nm laser) and a scan rate of 5 mm/s for a 1.49 wt % Ag content. This enhanced photothermal characteristic of the nanocomposite, which allows printing at low radiation intensities, is attributed to the efficient coupling of light to the AgNW plasmon modes and the high dispersion of nanowires in the polymer. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47670.

Monomer casting nylon/graphene nanocomposite with both improved thermal conductivity and mechanical performance

For high speed transmission devices, there is an urgent demand for MC nylon with high thermal conductivity and high mechanical strength simultaneously. In this study, the MC nylon/graphene nanocomposite has been prepared via pre-dispersed method, which was beneficial to distribute graphene uniformly in the MC nylon matrix. The thermal conductivity of the nanocomposite with 1.0 wt% graphene was 93% higher than that of the pure MC nylon. The impact strength of MC nylon/0.8 wt% graphene nanocomposite increased by 53%. The thermal stability of the MC nylon/graphene nanocomposites has also been improved. We attributed the excellent properties of MC nylon/graphene nanocomposites to the uniform dispersion of graphene in MC nylon matrix, which was confirmed by TEM and SEM characterization. This work provides an effective way for graphene dispersion and obtained MC nylon/graphene nanocomposites with excellent thermal and mechanical properties.

Thermal stability and mechanical properties of ethylenediamine‐modified GO/co‐polyamide nanocomposites

We describe ethylenediamine‐modified graphene oxide (GO)/co‐polyamide (GO‐EDA/CO‐PA) nanocomposites prepared via solution blending with EDA‐modified GO (GO‐NH2/EDA). GO was prepared via the improved Hummers method, and EDA was used to modify the GO to add amine groups to graphene. X‐ray diffraction, Fourier‐transform infrared spectroscopy and atomic force microscope analysis showed that the thickness of GO‐NH2/EDA was 1.2 nm. Amino functional groups were introduced onto the GO sheets. Due to the steric hindrance effect of the amino on modified graphene as well as the strong, specific interactions between aminos and carboxyls on CO‐PA, the GO‐NH2/EDA filler was homogeneously dispersed in the matrix, and the interface reaction was effectively improved. The GO‐NH2/EDA could change the crystal structure of pure nylon and the glass transition temperature (Tg). The mechanical properties of the nanocomposites increased dramatically when the GO‐NH2/EDA content is 0.6 wt%. The tensile strength and yield strength of the nanocomposites increased by 50.3 and 134.8%, respectively. The effects of interfacial interaction, increased crystallization, and prevention of agglomeration of GO‐NH2/EDA improved the thermal properties of the GO‐EDA/CO‐PA nanocomposites. This is because the 50% thermal degradation temperature (T‐50%) and the thermal degradation temperature (Td,max) of the nanocomposites increased by 16 and 15°C when the GO‐NH2/EDA content is 0.8 wt%. The nano‐filler improves the thermal diffusivity of the nylon matrix at low temperature. POLYM. COMPOS., 40:3315–3324, 2019. © 2018 Society of Plastics Engineers

Study of mechanical properties under compression failure in reinforced composite materials produced by additive manufacturing

In this work, we study the mechanical properties under compression of composite materials with reinforced-rigid-matrix produced by additive manufacturing. The study considers different fiber orientations and number of reinforcement layers of the specimens. The experimental investigation was carried out for parts produced with a nylon matrix and fiberglass reinforcement. The composite material was manufactured through fused deposition modeling (FDM) in a Markforged Mark Two 3D printer, which allows the production of specimens satisfying the ASTM D3410 standards. Different filling patterns were analyzed (triangular, hexagonal and rectangular), as well as, the reinforcing fiber angles (0°, ±30°, and ±45°), and the number of reinforcement layers (6, 12 and 18). The different configurations are analyzed in order to establish their performance under compression. Results indicate that to obtain a highly resistant material, more layers should be added and the fibers oriented parallel to the load axis.

SPECIALTY POLYMERS AND DYNAMICALLY VULCANIZED ALLOYS FOR ULTRA LOW AIR PERMEABILITY TIRE INNER LINERS

ABSTRACT Brominated poly(isobutylene-co-p-methylstyrene) specialty elastomers (Exxpro™) or BIMSM (ASTM name) are unique in their low permeability to air combined with a low glass transition temperature, Tg,, and a saturated backbone; making them a choice elastomer for applications requiring air barrier properties. This behavior derives from the geminal dimethyl groups on every other carbon of the polyisobutylene (PIB) backbone causing modification in the bond angles of these chains, allowing them to pack more closely than other saturated hydrocarbons. Dynamically vulcanized alloys (DVAs), also known as thermoplastic vulcanizates (ASTM 5046) of Exxpro™ elastomer and nylon thermoplastic (Exxcore™ DVA), also referred to as BIMSM-Nylon DVA, have much lower permeability to air than BIMSM. The challenge is to maintain the elastomeric nature of the material by having a major volume fraction of BIMSM rubber, while approaching the excellent air barrier characteristics of nylon at a lower volume fraction of the thermoplastic matrix than the dispersed rubber phase. This problem was solved by introducing a functional oligomer that chemically reacts with the nylon. BIMSM-Nylon DVAs consist of submicron sized domains of BIMSM elastomer of tailored molecular structure, in a matrix of nylon and a chemically bound oligomer viscosity modifier. Thus, a reasonable elastomeric modulus is achieved, and the key performance properties of superior air barrier as well as low temperature fatigue resistance are well satisfied. Tire inner liners are the focused end use of BIMSM-Nylon DVA, where the novel material characteristics are targeted to achieve excellent air impermeability, durability, and lightweighting. Optimal combination of these properties is expected to deliver improved performance and sustainable benefits such as fuel economy and lower tire maintenance costs.

Exploration of specimen geometry and tab configuration for tensile testing exploiting the potential of 3D printing freeform shape continuous carbon fibre-reinforced nylon matrix composites

Now that the design freedom of printing of continuous fibre-reinforced polymers has become available, the recommendations on the specimens’ geometry and tab configuration to experimentally determine the elastic properties of conventionally manufactured composites are reviewed. To explore this design freedom, tensile tests for five types of specimen geometry and tabs were investigated. Continuous carbon fibre-reinforced Nylon specimens were printed using a Mark Two commercial 3D printer. Dumbbell shape specimens according to ASTM D638-14 with proposed radius dimension, 76 mm, and with enlarged radius, 244 mm to reduce stress concentrations at the fillet and avoid crack initiation were tested. Rectangular specimens according to ASTM D3039/3039M-14 outperform other specimen geometries. The effectiveness of printed end tabs was investigated. Even although 3D printing offers facilities for printing end tabs, there is no convincing evidence that the performance of specimen gripping is better and the printing is more time consuming and expensive. Rectangular specimens with paper end tabs work best and that is why they were used in the further characterization. The effect of alternating Nylon layers was also investigated and shows drastic reduction in stiffness. In a next step, the tensile properties of a set of eight rectangular specimens with 0° unidirectional layup were characterized and compared with conventionally manufactured composites. The tensile properties for different fibre orientations were also determined. The effect of fibre location and microstructure was studied bringing important insights to the promising 3D printing but also revealing challenges to overcome (e.g. inhomogeneity in fibre distribution) to be able to fully explore the design freedom.

Enhanced Bonding via Additive Manufacturing‐Enabled Surface Tailoring of 3D Printed Continuous‐Fiber Composites

Additive manufacturing (AM) of composites, particularly continuous fiber composites as studied here, is emerging as a new paradigm for creating advanced structures. Traditional machining and joining approaches will evolve or be fully displaced by AM approaches, and here the authors introduce a seminal investigation into AM‐enabled bonding/joining of continuous fiber composite laminates/multilayers. The AM‐enabled tailoring approach volumetrically increases surface area available for bonding by ∼150% by printing lines of continuous Nylon matrix filaments at an infill density of 50% to create a porous (∼50 vol%) bonding surface, rather than the conventional/baseline solid (100 vol%) surface approach. The AM‐tailored multilayers show improvements relative to the baseline single‐lap‐joint (SLJ) multilayer, and versus the industry‐standard surface preparation approach: 550% and 145% increases in ultimate strength, 10 000% and 800% increases in toughness, respectively, while maintaining joint stiffness. Benchmark mechanical performance data is established via the AM‐tailored bonding approach for carbon, glass, and Kevlar continuous fiber reinforced additively manufactured composite SLJ multilayers. AM‐enabled enhanced joining, such as the concept demonstrated here, is critical as AM components are increasingly being joined, both to each other and to other (non‐AM, different AM, etc.) structures in advanced applications.

Microstructure and mechanical properties of three dimensional-printed continuous fiber composites

Additive manufacturing processes have a demonstrated capacity for flexible production of metal and polymer components. More recently, capabilities for three dimensional printing of continuous fiber reinforced composites were developed. As with printed metal and polymer materials, printed composites will exhibit a unique microstructure with morphological features and process artifacts that manifest on multiple length scales. The aim of this research was to investigate the microstructures of various printed continuous fiber composites and determine linkages to consequent mechanical properties such as stiffness and strength. Samples investigated in this study comprised unidirectional carbon fibers in nylon matrix, unidirectional Kevlar fibers in nylon matrix, and Kevlar fibers in nylon matrix aligned at ±45° directions. Tensile properties of the samples were evaluated along with comparison to expected properties. Fiber volume ratios were analyzed by thermogravimetric analysis. Scanning electron microscopy and optical microscopy were used to observe and characterize the hierarchical microstructure. Both strength and stiffness were approximately 30–40% weaker than traditionally produced composites, owing to features such as imperfect interfaces between printed layers, microvoids, incomplete fill density, and similar process artefacts. Future work will investigate mitigation of such effects through process modifications and post-processing to produce higher performance printed composites.

Poly (N-vinyl imidazole) gel-filled membrane adsorbers for highly efficient removal of dyes from water

Energy-efficient and time-saving process for recovery of hazardous dyes from wastewater is highly desired in dyeing industry. In this work, poly(N-vinyl imidazole) (PVI) gel-filled membrane adsorbers were developed for highly efficient recovery of dyes through adsorption filtration. The membrane adsorbers were fabricated via dip-coating of Nylon macroporous membranes in PVI solutions followed by quaternization crosslinking with p-xylylene dichloride (XDC). Physicochemical characterizations indicated that PVI gel was successfully filled and fixed inside the Nylon matrix. In optimized conditions. The treating capacity of membrane adsorbers to typical dye sunset yellow (25 ppm of the feed concentration) reached up to 197 mg/g with the removal ratio >99%. Both the treating capacity and the removal ratio were kept steady even when the permeation flux was as high as 1000 L/m2 h. The membrane adsorbers developed in this work were able to not only remove anionic dyes from water, but also separate anionic dyes from cationic ones. The zeta potential and adsorption tests showed that the electrostatic interaction between PVI gel and dye molecules was responsible for the high removal efficiencies to anionic dyes. The membrane adsorbers can be regenerated effectively with NaOH solution and demonstrated good stability in both acidic and alkaline conditions.

Elastic properties of 3D printed fibre-reinforced structures

This paper aims to evaluate the elastic properties of fibre-reinforced polymer (FRP) structures printed by three-dimensional (3D) printing technology. Both experimental and theoretical approaches are adopted to investigate the performance of FRP 3D-printed structures and predict their elastic properties. Three types of FRP materials were considered in this study including Carbon, Kevlar and Glass printed in selected arrangements of fibre filaments and Nylon matrix. An analytical model was developed based on the Volume Average Stiffness (VAS) method to predict elastic properties of 3D printed coupons, while the numerical model was developed using Abaqus to predict the failure modes and damage in the FRP 3D-printed coupons tested in this study. A parametric study was carried out to develop the mathematical expressions for calculating elastic properties of FRP 3D-printed structures. The parametric study indicates that the level of fibre reinforcements and their orientation arrangement have significant effects on the structural performance of FRP 3D-printed composite sections.

Mechanical properties of compression‐molded electrospun silica fiber/nylon‐6 composites

In this study, we utilized electrospun silica fibers (ESFs) as reinforcement in sandwiched nylon‐6 composites. The silica fibers were fabricated via electrospinning of sol‐gel precursor, prepared from tetraethyl orthosilicate. The process yielded non‐woven silica fiber mats with fiber diameter about 350 nm, which is much smaller than conventional glass fibers. Each ESF mat was sandwiched in between two nylon‐6 sheets and the layers were compression‐molded to produce a composite sample. These composites were prepared with varying silica fiber content, approximately at 0, 0.5, 1.0, and 1.9 wt%. The ESF blended well and chemically bonded with the nylon matrix, as observed through scanning electron microscopy and Fourier transform infrared spectroscopy. Tensile tests revealed that tensile modulus and tensile strength increased with ESF content. Notch Izod impact test showed that impact strength also increased with ESF content. The tensile and impact properties were significantly improved, considering the use of such low silica fiber percentages, which could be due to ultra‐fine fiber diameter and fiber continuity. From flexural test, however, flexural modulus and flexural strength decreased slightly by the addition of ESF. Specimen geometry and fabrication process play important roles in governing the composites mechanical behavior. POLYM. COMPOS., 40:1123–1131, 2019. © 2018 Society of Plastics Engineers