Short Glass Research Articles

Defining the Effect of a Polymeric Compatibilizer on the Properties of Random Polypropylene/Glass Fibre Composites

Random polypropylene composites reinforced with short glass fibres have been successfully fabricated by melt-mixing. Polypropylene grafted with maleic anhydride (PP-g-MA) was added to the composites, which was expected to act as a compatibilizer and greatly limit the negative effects known to arise from the feeble polymer matrix/glass fibre interfaces. The effect of compatibilizer concentration on the structural, mechanical and thermal behaviour of the composites has been investigated. The results revealed an improvement of the glass fibre/matrix interaction upon the addition of the compatibilizer, which resulted in enhancing the overall material stiffness and the ability of the matrix to store energy. In particular, the lowering of the glass transition and the investigation of the fracture surfaces of the composites confirmed the improved PPR/fibre adhesion. Examination of the tensile elongation indicated the improvement of the Young’s modulus and yield strength with the addition of PP-g-MA, while the storage modulus was also shown to be significantly increased. These results confirmed the versatility and efficiency of the approach presented in this work to improve the thermomechanical properties and sustainability of PPR and promote its usage in industrial applications and commercial manufacturing.

Assessment of fiber orientation models predictability by comparison with X-ray µCT data in injection-molded short glass fiber-reinforced polyamide

Assessment of fiber orientation models predictability by comparison with X-ray µCT data in injection-molded short glass fiber-reinforced polyamide

Fatigue behaviour of 25% wt. short glass fibre reinforced recycled Polypropylene filled with mineral filler in presence of notches

An experimental investigation is presented regarding the fatigue behaviour of notched and plain specimens made of 25% wt. short glass fibre reinforced recycled Polypropylene filled with mineral filler. Plain and double-edge notched specimens (with notch radius ranging from 0.2 mm to 10 mm) were produced by injection moulding and tested under tension-compression fatigue to highlight the effect of the notch root radius and notch geometry. During the fatigue tests, the damage evolution was monitored using a traveling microscope to define the number of cycles spent for the fatigue crack nucleation. First, the fatigue tests were reanalysed in terms of net-stress amplitude and the traditional stress-life curves for each specimen's geometry were found. Then, an energy-based approach was proposed for the assessment of fatigue life spent for the crack nucleation. The model is conceptually based on the actual damage evolution observed during the fatigue tests, which was according to the technical literature: the initiation of a macro crack results from the accumulation of damage in the matrix. Thus, the strain energy density evaluated in the matrix and averaged on a structural volume embracing the notch tip was adopted as fatigue damage index to correlate in a single scatter band the fatigue data of plain and notched specimens.

Multiscale Analysis of Composite Structures with Artificial Neural Network Support for Micromodel Stress Determination.

Structures made of heterogeneous materials, such as composites, often require a multiscale approach when their behavior is simulated using the finite element method. By solving the boundary value problem of the macroscale model, for previously homogenized material properties, the resulting stress maps can be obtained. However, such stress results do not describe the actual behavior of the material and are often significantly different from the actual stresses in the heterogeneous microstructure. Finding high-accuracy stress results for such materials leads to time-consuming analyses in both scales. This paper focuses on the application of machine learning to multiscale analysis of structures made of composite materials, to substantially decrease the time of computations of such localization problems. The presented methodology was validated by a numerical example where a structure made of resin epoxy with randomly distributed short glass fibers was analyzed using a computational multiscale approach. Carefully prepared training data allowed artificial neural networks to learn relationships between two scales and significantly increased the efficiency of the multiscale approach.

Development of Screw-Based 3D Printing Machine and Process Experiments for Short Fiber Reinforced Polymer Composites

3D printing is one of the flexible additive manufacturing (AM) processes that can be used to fabricate parts from various types of materials such as polymers, metal, and ceramic. 3D printing process is one of the famous techniques for printing the product from the filament causing material degradation. Granule-based 3D printing or screw-based material extrusion 3D printing is an alternative process that can create the parts from plastic or composite granule raw materials. However, there are limited use and study in the designation of granule-based 3D printing and process parameters including material temperature, heat bed temperature, nozzle size, and printing speed. These process parameters play a significant role in the properties of 3D printing parts. Some parameters cannot be adjusted in the commercial 3D printing process. Thus, the purposes of this study are to develop a screw-based material extrusion 3D printing machine that can freely adjust the process parameters and to investigate the effect of 3D printing parameters on the appearance and mechanical properties of printed parts. Pellets of neat acrylonitrile butadiene styrene (ABS) and short glass fiber/ABS composites are used in the experiments. Six process parameters were studied, including % fiberglass, printing temperature, printing speed, nozzle size, % Infill, and heat bed temperature. Each parameter has 3 levels, which were designed by the Taguchi L18 method. The results were evaluated by the main effect plot method and showed that the printing speed, nozzle size, and %fiberglass are the top 3 parameters that affect tensile strength. The nozzle size, %infill, and %fiberglass are the top 3 parameters that affect Young’s modulus. The granule-based 3D printing machine was completely developed; however, the extruded plastic line from the nozzle was difficult to control resulting in poor product quality. Thus, the feedback control for controlling the screw-extruder speed and temperature will be developed in future work.

Non-Isothermal Crystallization Kinetics and Activation Energy for Crystal Growth of Polyamide 66/Short Glass Fiber/Carbon Black Composites.

This study presents the effect of the addition of 0.4 wt.% carbon black (CB) to polyamide 66 (PA66) containing 30 wt.% short glass fibers (GFs) on the behavior of composite thermal crystallization. Composites were studied by differential scanning calorimetry analysis (DSC) at different cooling rates using wide-angle X-ray scattering (WAXS) and scanning electron microscopy (SEM). This thermal crystallization study highlights the nucleation effect of GFs that promote PA66 crystallization by significantly increasing crystallization kinetics and rates. The activation energies (Eas) calculated by model-free (FWO; KAS) and model-fitting (Kissinger method and C-R method) approaches showed that the combination of both GF and CB decreases the activation energy with respect to neat PA66, meaning that the presence of both additives facilitates crystallization. The Coats-Redfern and Criado methods showed that the crystallization of neat PA66 and related composites follows the second-order reaction, i.e., the decelerated reaction, evidencing compatibility between GFs and the matrix.

Compression properties and constitutive model of short glass fiber reinforced poly-ether-ether-ketone (PEEK)

To analyze the deformation behavior of short glass fiber-reinforced poly-ether-ether-ketone (SGFR-PEEK) under various conditions through numerical simulations, it is crucial to construct a constitutive model that can describe its stress–strain behavior over a wide range of strain rates and temperatures. In this study, quasi-static compression tests were conducted on SGFR-PEEK composites with varying mass fractions, and dynamic tests were performed using a Split Hopkinson Pressure Bar to acquire the material's compressive stress–strain response under quasi-static and dynamic conditions. The results indicate that, under compression, the yield stress of SGFR-PEEK composites increases with an augmentation in glass fiber content, rises with increasing strain rate, and decreases with elevated temperature. Based on experimental findings, a modified Johnson–Cook constitutive model was established to characterize the mechanical performance of SGFR-PEEK. In comparison to the traditional Johnson–Cook intrinsic structure model, the modified model takes into account the glass fiber mass fraction as comprehensively as possible and better predicts the material's flow behavior at high strain rates. Finally, this modified constitutive model was implemented in the ABAQUS software using the user-defined subroutine VUMAT to simulate the compression behavior of SGFR-PEEK composites under different loading conditions, and the model was validated. This research provides valuable insights for the practical application of SGFR-PEEK composites in engineering.

Development and characterization of short glass fiber reinforced-waste plastic composite filaments for 3D printing applications

In the present study, a thermoplastic-reinforced composite filament for 3D printing applications was created by mixing short glass fibers (SGF) with the thermoplastic matrix made from plastic waste. Short glass fiber-reinforced recycled high-density polyethylene (rHDPE) and recycled polyethylene terephthalate (rPET) blend thermoplastic composite filaments were first prepared by a plastic extrusion machine. The produced filaments' physical, mechanical, and thermal properties were investigated. After achieving the desired filament, a 3D printing technology called material extrusion was utilized to create 3D sample parts. The mechanical properties of each printed sample were analyzed following ASTM standards, and their morphological structures were also studied at various weight percentages (pure rHDPE, rHDPE/rPET (75/25 %), rHDPE/rPET reinforced with 15 % SGF, and rHDPE/rPET reinforced with 30 % SGF wt%). From the study, a 52 % increase in tensile strength, 32 % in Young's modulus, and a 50 % reduction in elongation with the addition of 30 wt% of SGF to rHDPE/rPET were noted compared to pure rHDPE. Generally, 3D printable composite filaments can be developed through the incorporation of SGF into plastic waste. This has tremendous advantages for solving environmental pollution and achieving sustainable development.

Comprehensive analysis of 3D printed PA6.6 and fiber‐reinforced variants: Revealing mechanical properties and adhesive wear behavior

AbstractWhile 3‐dimensional (3D) printing technology is advancing rapidly, commonly used filament materials are struggling to meet growing expectations. Polyamide (PA) is a material with high potential to replace commonly used low‐performance filament materials, thanks to its cost‐effectiveness and optimal material properties compared to advanced engineering materials. To explore this potential, the thermal, thermomechanical, and mechanical properties (at different temperatures), as well as the wear characteristics, of PA, short carbon fiber reinforced‐PA (SCFR‐PA), and short glass fiber reinforced‐PA (SGFR‐PA) filaments were comparatively examined in this study. Differential scanning calorimeter analysis (DSC), Dynamic Mechanical Thermal Analysis (DMA), uniaxial tensile tests, and Shore D hardness tests were conducted on the 3D printed specimens. The yield strength decreased by 48% and 73%, respectively, for neat PA as compared to room temperature when tested at 40 °C and 60 °C, while for SCFR‐PA, it decreased by 40% and 60%, and for SGFR‐PA, it decreased by 33% and 48%, respectively. The findings obtained from wear tests conducted on both bottom and top surfaces have demonstrated that glass reinforcement yields better results than carbon reinforcement. The experimental findings have been compared with SEM images, revealing their consistency.Highlights This study focuses on the performance evaluation of 3D printed PA and its composites. The mechanical properties of the materials at different temperatures were compared. Adhesive wear behavior is not directly related to fiber type, wear surface or hardness. Morphological analysis was conducted to elucidate the influence of fiber type on mechanical properties and wear behavior.

Effects of mechanical recycling on the properties of glass fiber–reinforced polyamide 66 composites in automotive components

Abstract In this study, we aimed to reveal the effective reusability of waste generated during the injection molding process of polyamide 66 (PA66) reinforced with 30 wt% of short glass fiber (PA66-GF30) widely used in the automotive industry. PA66-GF30 was subjected to the three mechanical recycling cycles, including regranulation and reinjection molding steps, and the recycled materials obtained in each of these cycles were included at the ratios of 15, 20, 25, and 30 wt% to the virgin composite. Thermogravimetric analysis and differential scanning calorimeter analyses showed that the number of recycling cycles and recycled material content in the composite had no significant change in the thermal stability and crystallinity degree of the PA66-GF30. The average fiber length determined by optical microscope analysis shifted to lower values from 300–350 to 150–250 μm by increasing the number of recycling cycles and the recycled material content. The fact that the recycled material content in the composite exceeds 25 wt% and the recycling cycle is applied three times played a key role in changing the mechanical and melt flow behaviors of the composite. Tensile strength, elastic modulus, and impact energy slightly decreased while the elongation at break and melt flow index increased.

Local defect formation in short glass fibre reinforced polymers – micro-mechanical simulations and interrupted in-situ experiments

Discontinuous fibre reinforced polymers are widely used in various industry sectors and often replace conventional materials, due to lower production costs and their lightweight structure. For improvement of the component design, detailed knowledge of the failure mechanisms are necessary. To better understand the defect formation and thus the micro-mechanics, the strain behaviour in single fibres was analysed by micro-mechanical simulations of Representative Volume Elements (RVE). Therefore, selected fibres – similar orientated as in the real structure – were chosen for detailed analysis. Additionally, the defect formation next to selected fibres was investigated by X-ray computed tomography (CT). Furthermore, the critical fibre length was estimated based on the protruding fibre length of the fracture surface. Overall the simulation results correspond to theory. However, the detailed local inspection of the experimental volume data showed a rather strong influence of neighbouring fibres.

Toward tailoring the mechanical and dielectric properties of short glass fiber‐reinforced epoxy composites

AbstractGlass fiber‐reinforced polymer‐matrix (GFRP) composites are used to manufacture devices such as radomes, electrical insulators, and radar‐absorbing structures, many of which are used in applications with strict mechanical and dielectric property requirements. As such, designs and properties of GFRP composite materials should be regularly improved to guarantee their safe operation and meet their constantly evolving application requirements. In this study, glass fiber (GF) particles and epoxy resin 128 (EP‐128) were used to manufacture high‐performance EP/GF‐X composites with GF particle contents ranging from 5% to 40%. An investigation into their mechanical and dielectric properties revealed that EP/GF‐20 composite specimens presented the best mechanical performance with their bending strength and modulus reaching 159.68 MPa and 6521.92 MPa, respectively, and an average dielectric constant of 4.862 within the 10–105 Hz frequency range. A theoretical analysis of the EP/GF‐X composite specimens' dielectric constants using classic dielectric models based on the Lichtenecker, Bruggeman, Jaysundere‐Smith, and Maxwell‐Garnett rule‐of‐mixture equations indicated that the dielectric model based on the Bruggeman rule‐of‐mixture equation provided the dielectric constants closest to the measured values with a maximum deviation of less than −0.321% for EP/GF‐40 composites. This study provides a feasible strategy to control the mechanical and dielectric properties of GFRP composites.Highlights Glass fiber (GF) particles and epoxy 128 (EP‐128) resin were used to manufacture high‐performance glass fiber‐reinforced epoxy (EP/GF‐X) composites. The composite manufacturing process was carefully controlled to ensure uniform distribution and orientation of GF particles in the EP‐128 resin. The mechanical and dielectric properties of the manufactured EP/GF‐X composites were effectively tailored by controlling the content and distribution of GF particles in the EP‐128 resin matrix. The dielectric constants of the EP/GF‐X composites were measured experimentally and predicted using various theoretical dielectric models. The Bruggeman model provided the dielectric constants of the EP/GF‐X composites closest to the measured values.

Compressive Strength Testing of Glass-Fibre-Reinforced Tooth Crown Tissues After Endodontic Treatment

The objective of this study was to compare the effects of using short and continuous fibres for repairing compression-induced tooth crown damage. Human teeth were used for the study. They were upper medial incisors and maxillary first premolars lost due to periodontal causes. The teeth were divided into two groups with Hahnenkratt and short glass fibres. Teeth compressive strength tests were carried out. Then micro-CT imaging of the teeth and their fractures obtained after compression was performed. The teeth restored with Hahnenkratt’s glass fibre posts showed higher compressive strength than the teeth restored using the EverX Posterior material. The tooth’s most weakened and sensitive point after endodontic treatment was the cervical area of the tooth. All cracks were parallel to the root canal.

Effect of glass fiber reinforcement on compressive strength of photopolymer composite fabricated using vat‐photopolymerization additive technique: An experimental and modeling approach

AbstractShort or nanofillers‐reinforced composites increase the thermo‐mechanical characteristics of additive manufacturing (AM) base materials. Effective outputs were regulated via parametric optimisation and custom production. One of the most used AM method, Vat photopolymerization (VPP), creates complex and geometrically precise photopolymer parts. This study prepares photopolymer composite (PPC) samples with 2.0, 4.0, 6.0, and 8.0 volume percentages of short glass fiber (SGF) using an inter‐stage stirring method in DLP‐based VPP process. An adequate curing time and formable layer thickness were evaluated for the printability performance of SGF‐photopolymer composite. The 4.0% PPC‐sample showed a 20% higher compressive yield strength than pure photopolymer and other volume fractions. The consequences of increased strength values were assessed by the effect of stirring method and the fractography analysis of PPC specimen. The investigation additionally encompassed numerical simulations that employed an innovative technique for constructing and simulating three‐dimensional representative volume elements (RVEs). The RVEs were designed to replicate the experimental outcomes by randomly situating and orienting fillers within the matrix. The study employs the calibrated Three Network (TN) viscoplastic constitutive material model as the matrix property, and the simulation results demonstrate a margin of error of 5%–10% when compared to the experimental findings.Highlights Layer‐wise availability of SGFs through inter‐stage stirring method The exposure time and layer thickness were determined by Jacob's working curve Concept of RVE is used to combine individual SGF layers into a single layer SEM showed that increasing SGF layer resists cracking better than neat matrix Experimental data and numerical simulations are in good agreement

The effect of fiber content and aspect ratio on anisotropic flow front and fiber orientation for injection-molded fiber composites

Abstract In state-of-the-art predictive engineering software for injection molded fiber composites, it is challenging to discuss the effect of fiber properties, including fiber content and aspect ratio, on the shell-core fiber orientation and anisotropic flow front. Recently, the flow-fiber coupled model of informed isotropic (IISO) viscosity was proposed for simulating the realistic flow-induced fiber orientation. At present, one attempts to improve the IISO viscosity in relation to fiber content and aspect ratio. Therefore, injection molding simulations of 30 wt% and 50 wt% short glass fiber-reinforced Polyamide66 (30 wt% SGF/PA66 and 50 wt% SGF/PA66) are performed in the IISO flow-fiber couple 3D-FVM (three-dimensional finite volume method) computation under the fixed aspect ratio of a r = 20. As a result, the predicted fiber orientation distributions are in good agreement with related experimental data, while the core width is increased with fiber contents. In addition, the anisotropic ear flow occurs at the higher content. Based on shear viscosity of 30 wt% SGF/PA66, one can directly alter fiber content as 50 wt% SGF/PA66 in the IISO computation to anticipate the reliable trend of fiber orientation and flow behavior. When the a r = 20 short fiber is lengthened as the a r = 50 long fiber, the core obviously becomes the wider. It is significant to investigate the difference between the decoupled and coupled computation, as well as the influence of the flow-fiber coupled and fiber orientation model parameters.

Tribological characteristics and wear mechanisms of reinforced composites against steel

To explore the potential wear performance of commonly utilized hydraulic system polymer components, we investigated the effects of different working conditions on the frictional and wear behaviors of three polymer sealing materials in this study. Polytetrafluoroethylene (PTFE), nylon (PA), and polypropylene (PP) composites were prepared using copper (Cu) and glass fiber (GF) as fillers. The tribological and wear properties (wear rate, surface appearance, wear patterns) of the sealing composites were evaluated. The results showed consistent trends toward increasing average coefficient of friction as load and speed increased for PTFE. The incorporation of filler improved the wear resistance of the composites. The addition of Cu particles showed lower coefficient under higher load and sliding speed. PA with continuous glass fiber (CGF) sealing composites showed lower coefficient, less wear volume, and relatively smoother wear zone surfaces than PTFE-based composites or PP with short glass fiber (SGF). We propose that PA-CGF outperforms other materials in regards to fatigue and friction and wear even under extremely high silding speed,as well as sealing properties.

Microscopic failure characteristics and critical length of short glass fiber reinforced composites

Short glass fiber reinforced composites (SGFRC) are frequently used to manufacture parts with complex surfaces by injection or compression molding. It was found that the length of fibers is often reduced during the manufacturing processes. To understand the causes of the change in fiber length, ex-situ 3D CT images are taken from tensile experiments to extract the information of the microstructure of the SGFRC, including fiber length, orientation and breakage. In the calculation of the critical length, the Kelly model is modified to include the effect of the stresses at fiber ends and the mechanical effect of internal pore defects on the composites. It is found that the microscopic interaction of short fibers breaks longer fibers, until they are shorter than the critical length. Through comparisons, it is found that the modified Kelly model is more accurate in predicting critical length of short fibers. In this study, micro-failure modes, such as fiber pulling out, interface debonding, matrix damage and pore destruction, are all characterized by micro-CT and scanning electronic microscope to analyze the complex failure mechanisms. The micro failure modes are mainly attributed to the micro geometric features and mass fraction of short fibers.

Numerical simulation and experimental validation of ratchetting deformation of short fiber-reinforced polymer composites

This paper proposes a micromechanical model based on the finite element method (FEM) to analyze the ratchetting deformation of short glass fiber-reinforced polymer composites (SFRPCs). To reasonably consider the complex mechanical characteristics of the polymeric matrix under asymmetrical stress-controlled cyclic loading, a damage-coupled nonlinear viscoelastic-viscoplastic (VE-VP) cyclic constitutive model was constructed. The cyclic constitutive model of the matrix was introduced into the FEM model utilizing a user-defined material, and the corresponding experimental validation of the matrix was conducted. Subsequently, the cyclic constitutive model was introduced into the analysis of the micro-FEM model of the composites. The random orientation was considered to generate fibers in the FEM. Based on the analysis of the microscale representative volume element (RVE) model, the effects of different fiber content and cyclic peak stress on the ratchetting of SFRPCs were studied in detail. After validation, the effects of the fiber length and fiber stiffness on the ratchetting deformation of SFRPCs are discussed based on the developed micro-FEM model. The results show that the increase in the fiber length and fiber stiffness reduced the ratchetting deformation of SFRPCs within a specific content range. The model can assess the ratchetting deformation and damage evolution within the composites to provide more accurate predictions of the ratchetting deformation of SFRPCs and guide the expanded application of SFRPCs in structures.

Load-bearing capacity and wear characteristics of short fiber-reinforced composite and glass ceramic fixed partial dentures.

The aim of this study was to evaluate load-bearing capacity and wear performance of experimental short fiber-reinforced composite (SFRC) and conventional lithium-disilicate CAD/CAM fabricated fixed partial dentures (FPDs). Two groups (n = 12/group) of three-unit CAD/CAM fabricated posterior FPDs were made. The first group used experimental SFRC blocks, and the second group fabricated from lithium-disilicate (IPS e.max CAD). All FPDs were luted on a zirconia testing jig with dual-curing resin cement. Half of FPDs per group were quasi-statically loaded until fracture. The other half experienced cyclic fatigue aging (100.000 cycles, Fmax = 500 N) before loading quasi-statically until fracture. Fracture mode was examined using SEM. Wear test was performed using 15,000 loading cycles. Both material type and aging had a significant effect on the load-bearing capacity of FPDs. Experimental SFRC CAD without fatigue aging had significantly the highest load-bearing capacity (2096 ± 149N). Cyclic fatigue aging decreased the load-bearing capacity of the SFRC group (1709 ± 188N) but increased it for the lithium-disilicate group (1546 ± 155N). Wear depth values of SFRC CAD (29.3μm) were significantly lower compared to lithium-disilicate (54.2μm). Experimental SFRC CAD demonstrated the highest load-bearing capacity before and after cyclic fatigue aging, and superior wear behavior compared to the control material.

Material and mechanical characterization of recycled polypropylene reinforced with different weight percentages of short glass fiber developed by injection molding

The objective of this study was to develop short glass fiber-reinforced recycled polypropylene composites using injection molding technique with varying fiber percentages (0–50 wt%). The study aimed to evaluate the mechanical and material properties of the composites and their potential applications. To achieve this, polypropylene composite pellets were prepared using a low-cost and simple manufacturing method that involved plastic recycling using a crushing method and pelletizing with different weight percentages of short glass fiber using twin-screw extruder. The study conducted various analyses, such as melt flow index, capillary rhinometry, thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy. Results showed that the recycled polypropylene/short glass fiber composites exhibited improved heat resistance, crystallization rate, and thermal stability compared to the pure polymer. The best impact mechanical (about 3.65 ± 0.09 J/m) properties were obtained at 50 wt% of short glass fiber in the fabricated composites. Scanning electron microscope analysis indicated a uniform dispersion of short glass fiber in the polypropylene matrix. The potential applications of these composites were found in household appliances, industrial plastic products, and other areas. Overall, this study demonstrates the potential of short glass fiber-reinforced polypropylene composites as a cost-effective, environmentally friendly and sustainable alternative for various applications.