Short Glass Research Articles

Theoretical models for stiffness prediction of short fibre composites

The short natural fibre reinforced polymer matrix composites are a good cost-effective option in a multitude of non-structural applications. The estimation of elastic moduli of such composites is important during the initial design phase. In this work, a brief introduction to the theoretical models to determine elastic moduli of short fibre composites is presented. Various theoretical models like Halpin-Tsai model, Mori-Tanaka model with fibre orientation averaging, alongwith the rule-of-mixtures and the Hashin-Shtrikman bounds are employed to obtain the elastic properties of composites. Although some of these models have been used for short glass fibre composites, in this study, the applicability of these models to natural fibre composites has been explored. The elastic properties obtained from the theoretical model are compared with experimentally obtained values of injection moulded short jute fibre-polypropylene composites from our other work. The model which satisfactorily results in better elastic property predictions of short fibre composites amongst the presented theoretical models has been highlighted. It has been observed that the fibre orientation averaging is imperative to account for random fibre orientation and yield better elastic property predictions.

Short glass fiber reinforced polymer concrete with addition of waste cathode-ray tube (CRT) glass

This paper describes the use of CRT glass waste for the production of polymer concrete. The CRT glass was subjected to a multistage mechanical disintegration process, in a way that allowed obtaining grains smaller than 2 mm. A set of hybrid reinforced polymer concrete was produced by using: ground CRT glass, sand and cut glass fibers 4.5 mm and 12 mm long. The influence of the volume of fibers and the length of glass fibers on the properties of polymer concrete with 30% by volume of epoxy resin, acting as a binder was described. Tests of CRT glass were carried out, among others study of chemical composition, particle size distribution and analysis of grain morphology. For polymer concrete, the flexural strength and compressive strength were determined, and the open porosity, apparent density, and water absorption were examined. The test results showed that polymer concrete with the use of milled CRT glass is a good way to manage this problematic waste. The polymer concrete has several times better than traditional concretes and significantly lower porosity and water absorption, which makes this material advantageous in applications such as the production of thin-walled products and products exposed to water and chemical attack. The addition of chopped glass fibers leads to an increase in mechanical properties and also protects the material against rapid disintegration after exceeding the maximum tresses, which is extremely important for the safety of use of the structure in the event of a failure.

The role of mix design and short glass fiber content on mode-I cracking characteristics of polymer concrete

Suitable resistance against fracture and cracking is a primary requirement for using polymeric concrete materials in practical applications. The main aim of this research is to investigate the effect of mix-design on mode I cracking behavior. A total number of 72 different Polymer Concrete (PC) mix-designs made of four ingredients (epoxy resin, coarse silica aggregate, fine sand filler and chopped strand E-glass fibers) were considered for conducting fracture experiments using the Semi-Circular Bend (SCB) specimen. The weight percentages of the ingredients were varied in the following range: 17–25% resin, 75–81% fine and coarse aggregates and 0–2% glass fibers. The investigated mix-designs were categorized into six groups (ultra-high, high, medium-high, medium-low, low and ultra-low) in terms of the adhesive agent content (i.e. the ratio of resin plus fiber content to the weight of the whole mixture). The experiments showed the noticeable dependency of both fracture toughness and fracture energy values (KIf and GIf) on the PC mix-design. In addition, the effect of substituting 1 and 2% of resin content with glass fiber was investigated. It was found that adding the fiber cannot necessarily enhance the performance of PC mixture against cracking and for some mix-designs; the addition of fiber can even reduce both KIf and GIf values.

Comparison of Real and Simulated Fiber Orientations in Injection Molded Short Glass Fiber Reinforced Polyamide by X-ray Microtomography.

During injection molding of short glass fiber reinforced composites, a complex structure is formed due to the fiber movement. The resulting fiber orientation can be predicted using various simulation models. However, the models are known to have inadequacies andthe influence of process and model parameters is not clearly and comprehensively described. In this study, the aforementioned model and process parameters are investigated to determine the dependencies of the individual influences on the real and simulated fiber orientation. For this purpose, specimens are injection molded at different process parameters. Representative regions of the specimens are measured using X-ray microtomography and dynamic image analysis to determine the geometric properties of the fibers as well as their orientations. Furthermore, simulations are performed with the simulation software Moldflow® using different mesh types and densities as well as varying parameters of the MRD model to represent the real fiber orientations. The results show that different orientation areas arise in the samples, which cannot be represented with a simulation varying only one parameter. Several simulations must be carried out in order to represent flow regions occurring in the specimen as realistically as possible.

Effect of short glass fiber on shear capacity for shallow wide reinforced concrete beams

Shallow wide reinforced concrete beams are used in modern buildings especially in residential building structures. According to current Egyptian Code Practice 203-2018; the characteristic of a shallow wide concrete beam is that the cross-section width (b) over the effective depth (d) ratio is greater than two and the beam depth is less than 250 mm. Without any shear reinforcing contribution, the applied shear stresses in shallow wide beams must be less than the concrete shear strength. And only concrete provides shear strength. An experimental program was conducted to investigate the contribution of short glass fiber polymer reinforcement to shear strength in shallow wide beams under shear stress. The short glass fiber polymer reinforcement ratio was the main parameter in this study. And also, the contribution of web shear stirrups reinforces against shear stresses. The experimental program consisted of five simply supported reinforced shallow wide concrete beams. Test results show that the use of short glass fiber reinforced polymer has a great effect on shear strength capacity, mode of failure, and ductility of shallow wide concrete beams.

Toughening Mechanism Analysis of Recycled Rubber-Based Composites Reinforced with Glass Bubbles, Glass Fibers and Alumina Fibers.

Recycling of materials attracts considerable attention around the world due to environmental and economic concerns. Recycled rubber is one of the most commonly used recyclable materials in a number of industries, including automotive and aeronautic because of their low weight and cost efficiency. In this research, devulcanized recycled rubber-based composites are designed with glass bubble microsphere, short glass fiber, aluminum chip and fine gamma alumina fiber (γ-Al2O3) reinforcements. After the determination of the reinforcements with matrix, bending strength and fracture characteristics of the composite are investigated by three-point bending (3PB) tests. Halpin–Tsai homogenization model is adapted to the rubber-based composites to estimate the moduli of the composites. Furthermore, the relevant toughening mechanisms for the most suitable reinforcements are analyzed and stress intensity factor, KIc and critical energy release rate, GIc in mode I are determined by 3PB test with single edge notch specimens. In addition, 3PB tests are simulated by finite element analysis and the results are compared with the experimental results. Microstructural and fracture surfaces analysis are carried out by means of scanning electron microscopy (SEM). Mechanical test results show that the reinforcement with glass bubbles, aluminum oxide ceramic fibers and aluminum chips generally increase the fracture toughness of the composites.

Processing and Testing of Reinforced PA66 Based Composites.

The new requirements in different sectors, such as aerospace, automotive and construction, for lightweight materials have led to an increase in demand for composite materials suitable for use in high rate production processes, such as plastic injection. This makes it necessary to look for matrices and reinforcements that, in addition to being compatible with each other, are also compatible with the injection process. It is in this area of research where the work presented here arises. To meet the two requirements mentioned above, this study contemplates a battery of composite materials obtained by combining PA66 and fiberglass, in different proportions and configuration, both for the preparation of the matrix and for reinforcement. For the elaboration of the matrix, two options have been evaluated, PA66 and PA66 reinforced at 35% with short glass fibre. To obtain reinforcement, six different options have been evaluated; two conventional fiberglass fabrics (each with different density) and four hybrid fabrics obtained from the previous ones by adding PA66 in different configurations (two over-stitched fabrics and two other fabrics). The different composite materials obtained were validated by means of the corresponding adhesion, peeling and resistance tests.

Synthesis of a self-assembly amphiphilic sizing agent by RAFT polymerization for improving the interfacial compatibility of short glass fiber-reinforced polypropylene composites

This experimental study focuses on the development of an amphiphilic sizing agent to improve the interfacial adhesion and the mechanical properties of short glass fiber (GF)/polypropylene (PP) composites. To solve the critical compatible issue between the hydrophilic GF and the hydrophobic PP, we strategically utilized the reversible addition-fragmentation chain-transfer (RAFT) polymerization to self-assemble and synthesize an amphiphilic sizing agent. This surfactant-free sizing agent can create hydrogen bonds and electrostatic adsorption on GF surfaces and meanwhile can form molecular entanglements, alkyl cations, and σ-π conjugates with PP matrix. The FT-IR analysis shows that a large number of hydrogen bonds are formed on the sizing agent-GF interface. Additionally, the SEM micrographs of the composite fracture surfaces demonstrate strong interfacial compatibility between the sized-GF and the PP matrix. Comparing with the neat GF/PP composites, the tensile and flexural strength of the sized-GF/PP composites are increased by 25.8% and 33.1%, respectively. Their tensile strength and young's modulus are in close agreement to the analytical calculations. In short, this paper presents a new RAFT-based methodology to develop the amphiphilic sizing agents that are able to improve the interfacial compatibility of GF/PP composites and also can be transferred towards real applications for enhancing the mechanical properties of fiber-reinforced composites.

Polylactic acid/recycled wind turbine glass fiber composites with enhanced mechanical properties and toughness

AbstractThe amount of composite waste from decommissioned wind turbine blades grows rapidly and recycling solutions should be generated to overcome this environmental challenge. This research aims to further develop a recycling method to recover components of dismantled turbine blades by reusing them as reinforcement for new composites. Recycled short glass fibers from shredded blade composites are incorporated into polylactic acid (PLA) to fabricate a composite (15 wt% fiber) that could be used for 3D filament fabrication. To improve the mechanical properties of the composite, a coupling agent was employed to refine the interactions between PLA and recycled glass fibers at the interface of the two components and enhance the adhesion. Due to the inherent brittleness of PLA, which is aggravated with the addition of recycled glass fibers, a toughening agent involving chain‐end modification was incorporated into the composite to improve the toughness of the system. The concurrent outcome of the coupling agent and the toughener on the morphology, mechanical properties and thermal behavior of the composite was evaluated. The incorporation of 1,2,3,4‐butane tetracarboxylic acid and silane‐treating of the recycled fibers improved the strength by 30% and elongation at break and impact strength of the composite 3 and 2 times, respectively.

Impact and CAI behavior of SGF mat filled sandwich panels made from foam core and FRP facesheet

The interlaminar bonding property between the facesheet and foam core plays an important role in enhancing the impact damage resistance ability of sandwich panels. In this paper, we filled short glass fiber (SGF) mat between the facesheet and foam core to enhance their bonding strength. The newly designed sandwich panels were manufactured by vacuum-assisted resin injection processing. A series of SGF mat filled sandwich panels with glass and/or carbon fiber facesheets were manufactured. The low-velocity impact as well as the compression-after-impact (CAI) performence were investigated. Failure modes of the sandwich panels were analyzed. Low-velocity impact results show that SGF mat filled sandwich panels with pure glass fiber facesheet displayed the maximum contact force. In the CAI test, wrinkling of the facesheet, buckling of the foam, and debonding between them are the major failure modes. Compared with contrast samples, SGF toughened sandwich panels show the highest strength increase rate.

Denture composite reinforced with short polyethylene terephthalate fibers

AbstractPolymer matrix composite materials have found application in dentistry because of good mechanical properties, aesthetic, easy processing, and possibilities of the repair. Acrylates are materials used to make and repair dentures. Reinforcements in the form of short glass or polymer fibers are added to improve the mechanical properties of dental polymers. In this study, the processing of composite material with a polymer matrix from commercial auto‐polymerized acrylate Simgal, with reinforcement in the form of short poly(ethylene terephthalate) (PET) fibers was examined. Samples were processed in three series: pure Simgal, Simgal/PET 1 wt% and Simgal/PET 3 wt%. The influence of the reinforcement in the form of short PET fibers on the mechanical properties of composite materials was investigated. Strength and hardness were tested by impact testing and Vickers microhardness, and it was shown that there is an increase in absorbed energy and hardness. The modulus was reduced by the addition of PET fibers and by increasing the amount of fibers in the composite. The increase in the amount of PET fibers also resulted in a smaller loss of surface mass of the samples compared to the pure matrix by 63% and 93%, respectively. Cavitation test revealed better cavitation resistance of composites than the pure acrylate.

On short glass fiber reinforced thermoplastics with high fiber orientation and the influence of surface roughness on mechanical parameters

Injection molding is a common process for manufacturing thermoplastic polymers. Preconnected to fabrication, mechanically loaded parts are examined in structural simulation. A crucial prerequisite for a valid structural simulation for any material is the underlying material data. To determine this data, different phenomena must be considered such as influences of load type, strain rate, environmental conditions and in case of fiber reinforced materials the fiber orientation (FO) in the considered area. Because of rheological effects, injection molded parts often possess a non-homogeneous FO distribution. This makes it challenging to create testing plates for specimen extraction with a well-defined FO over thickness and width in the considered area. In this paper, a novel testing part is introduced with an unidirectionally oriented testable area. It shows a FO degree of more than 0.75, which has been validated with μ-CT measurement and two thermoplastic materials: polyamide and polybutylene terephthalate, both reinforced with 30 weight percent of short glass fibers. In order to resolve influences of the already addressed FO distribution in injection molded parts, tensile test specimens need to be extracted out of specially designed plates via milling and cannot be injection molded directly. Experiments were carried out to study possible effects of preparation on the mechanical properties of specimens with both materials and two milling parameter sets. The first milling parameter set creates reproducible surface roughnesses, whereas the second parameter set shows a correlation between FO and roughness value: when milling perpendicularly to the main FO lower roughnesses are reached than milling in fiber direction. Uncertainties of the normalized rupture strain from orthogonally extracted specimens seem to be larger than the values from those extracted in fiber direction.

The influence of preheating temperature on the mechanical properties of injection-overmolded hybrid glass fiber reinforced thermoplastic composites

Thermoplastic overmolding technique is an advanced integrated manufacturing technology to fabricate hybrid fiber reinforced thermoplastic composites (hybrid composites) components in which short fiber reinforced thermoplastics are injected onto the surface of thermoformed continuous fiber reinforced thermoplastic (CFRT) laminate (organosheet). To further clarify the bonding mechanism between the heterogeneous interface of short and continuous glass fiber reinforced thermoplastic composites, a series of experimental tests and molecular dynamic (MD) simulations were conducted to investigate the preheating temperature of organosheet on mechanical properties of hybrid composites. The experimental results reveal that the surface roughness of organosheet is increased with raising the preheating temperature, resulting in the enhancement of mechanical interlock at the bonding interface. The interface region in SEM observation is gradually disappeared due to molecule diffusion. Simulation results show that both diffusion coefficient and interfacial bonding energy are clearly improved with preheating temperature. Compared with the non-preheating condition, the flexural strength of the hybrid composite is increased by more than three times when the preheating temperature is set as 220 °C by IR heater. Moreover, the fracture mode of hybrid composites has been proven to change with the preheating temperature.

Mechanical Behavior Modelling and Filler Geometry Effect of Glass Filler Reinforced Starch-Epoxy Hybrid Matrix Composites.

The aim of the present study is to investigate the inclusion geometry and concentration effect on the quasi-static properties of a starch-epoxy hybrid matrix composite. The composites investigated consisted of a starch-epoxy hybrid matrix reinforced with four different glass inclusions such as 3 mm long chopped strands, 0.2 mm long short glass fibers, glass beads (120 μm in diameter) and glass bubbles (65 μm in diameter) at different concentrations. The flexural modulus and the strength of all materials tested were determined using three-point bending tests. The Property Prediction Model (PPM) was applied to predict the experimental findings. The model predicted remarkably well the mechanical behavior of all the materials manufactured and tested. The maximum value of the flexural modulus in the case of the 3 mm long chopped strands was found to be 75% greater than the modulus of the hybrid matrix. Furthermore, adding glass beads in the hybrid matrix led to a simultaneous increase in both the flexural modulus and the strength.

Development and verification of mechanical characteristics of a composite material made of a thermoplastic matrix and short glass fibers

The paper presents the results of computer modeling and prediction of the mechanical properties of composite materials with a polycarbonate matrix filled with short glass inclusions. At the micro-level, the influence of the volume of inclusions on the mechanical properties of the designed composite based on polycarbonate matrix is studied in the DIGIMAT (France) program. It was found that with a ratio of the sizes of inclusions in the range of 468÷60, the particles have a needle shape, and the material with such inclusions has a higher stress limit and elastic modulus than with a shape coefficient less than 50. The components of the fiber orientation tensor were also determined, at which the values of computer modeling are in good agreement with experimental data. The influence of the size of the finite element grid on the characteristics of the composite at the macro level was studied, and recommendations were given for choosing the size of the face of the finite element. The adequacy of computer models was confirmed by the results of field tests. The paper presents the results of testing flat samples made by injection molding technology. Mechanical tests were carried out for three variants of samples made of composite material based on a polycarbonate matrix with 10 %, 20 % and 30 % inclusions. The discrepancy between the experimental and computer results for samples with 10 %, 20 % content of short chopped fibers is explained by the influence of technological factors on the properties of the material at the macro-level. The conducted research allowed us to develop a computer modeling technique used at the stage of development of polymer composites based on thermoplastic matrices with short glass inclusions

Effect of geometrical parameters and tool pattern of multi-tooth sawing on cutting of sheet molding compound composite: FE study

Short glass fiber composites, particularly sheet molding compound (SMC) materials, are becoming increasingly important alternative in various contemporary aerospace, automotive, and electronic applications. For these manufacturing industries, the quality of the machined SMC composite is still a challenging target. The article proposes a new tool design with an offset between teeth to minimize friction, limit damage and promote chip removal when drilling composite materials. The effects of the tool’s geometric parameters, especially the rake, the inclination and the complementary side cutting edge angles on the material removal process, as well as the cutting and thrust forces, are investigated. A 3D finite element model of a representative multi-tooth tool is developed using the ABAQUS\\Explicit code. The results show that fine-tuning the geometric parameters of the tool reduces the induced machining damage and enhances the chip removal and the flow evolution. The rake angle has a significant influence on the cutting and thrust forces. However, both forces are insensitive to the inclination angle. The complementary side cutting edge angle influences only the thrust force. The presented outcomes not only give insights into the cutting process, but also improve the SMC machinability.

The Effect of Fibers’ Length Distribution and Concentration on Rheological and Mechanical Properties of Glass Fiber–Reinforced Polypropylene Composite

This article aims to investigate the effect of dispersion and uniformity of fiber length distribution on the rheological and mechanical behavior of polypropylene reinforced with short glass fiber. The composites were prepared through melt compounding with three various glass fiber concentrations using a twin-screw extruder. Multiple extrusion processing was used to alter and manipulate the fibers’ length inside the composites. The fiber length distribution was analyzed via the photomicrograph technique. Rheological measurements indicated that the molten samples were visco-plastic fluids and the Herschel–Bulkley model is the best model for fitting on the rheological behavior diagram. Variables of the fitted model are noticeably altered by the fiber length distribution. Moreover, rheological assessments revealed that the non-Newtonian behavior of the molten composites significantly diminished after the second extrusion processing, while it did not have much effect on the fiber length reduction. In the second phase, tensile and flexural properties were determined to detect the mechanical properties. The results indicated that the tensile strength of the composite has a direct relation with the fiber length distribution factor while the flexural strength is independent of fiber length. Furthermore, the highest tensile and flexural strength attained from the composite containing the highest fiber volume fraction.

Process Behavior of Short Glass Fiber Filled Systems during Powder Bed Fusion and Its Effect on Part Dimensions

In powder bed fusion of polymers, filled systems can provide a wide range of part properties, which is still a deficit in additive manufacturing, as the material variety is limited. Glass fiber filled polymers provide a higher strength and stiffness in parts; nevertheless, the process behavior differs from neat polymer systems. In this study, the optical properties and their effect on the part dimensions are analyzed. A higher glass fiber content leads to an increased absorption of laser energy, while the specific heat capacity decreases. This results in larger part dimensions due to higher energy input into the powder bed. The aim of the study is to gain process understanding in terms of ongoing mechanisms during processing filled systems on the one hand and to derive strategies for filled polymer systems in powder bed fusion on the other hand.

Effect of fiber loading on mechanical, physical behavior of thermoplastic blend composites

The short fiber reinforced hybrid thermoplastic blend composites is most widely used in aerospace & automobile industries. Individual fibres and their hybrid effect on mechanical characterisation are the focus of this article. The materials used for the study are Polyamide66 (PA66), Polypropylene (PP), Short glass fibers (SGF) and Short basalt fibers (SBF). The material system used for the study are Blend (PA66/PP), Blend/SGF, Blend/SBF and Blend/SGF/SBF. Melt mix method with twin screw extruder is used to manufacture composite material systems. ASTM standards were used to evaluate the composites physical and mechanical properties, such as hardness, density, tensile, flexure, and impact strength. The experimental data indicated that the mechanical properties particularly tensile and flexural strength enhanced significantly by the insertion of short fibers into thermoplastic blend. Further the impact properties reduced due the brittle nature of the fibers in the blend composites. The density as well as the hardness of the short fiber reinforced composites increases with respect to the blend. The failure mechanism of the composites due the mechanical characterization is observed through the SEM pictures.

Effect of Short Fibres in the Mechanical Properties of Geopolymer Mortar Containing Oil-Contaminated Sand.

Sand contaminated with crude oil is becoming a major environmental issue around the world, while at the same time, fly ash generated by coal-fired power stations is having a detrimental effect on the environment. Previous studies showed that combining these two waste materials can result in an environmentally sustainable geopolymer concrete. Incorporating sand contaminated with crude oil up to a certain level (4% by weight) can improve the mechanical properties of the produced geopolymer concrete but beyond this level can have a detrimental effect on its compressive strength. To overcome this challenge, this study introduces short fibres to enhance the mechanical properties of geopolymer mortar containing fine sand contaminated with 6% by weight of light crude oil. Four types of short fibres, consisting of twisted polypropylene (PP) fibres, straight PP fibres, short glass fibres and steel fibres in different dosages (0.1, 0.2, 0.3, 0.4 and 0.5% by volume of geopolymer mortar) are considered. The optimum strength was obtained when straight PP fibres were used wherein increases of up to 39% and 74% of the compressive and tensile strength, respectively, of the geopolymer mortar were achieved. Moreover, a fibre dosage of 0.5% provided the highest enhancement in the mechanical properties of the geopolymer mortar with 6% crude oil contamination. This result indicates that the reduction in strength of geopolymer due to the addition of sand with 6% crude oil contamination can be regained by using short fibres, making this new material from wastes suitable for building and construction applications.