Fiber Rovings Research Articles

Experimental Permeability and Porosity Determination of All-Oxide Ceramic Matrix Composite Material.

This paper presents an investigation into the water permeability of an all-oxide ceramic matrix composite. To determine the parameters and characterize the water permeability of the ceramic composite material, an experimental study was carried out in which a dedicated test rig was constructed and commissioned. A total of five different configurations of composite tubes were tested. They differed in fibre roving strength, winding angle, fibre bundle arrangement during winding, and matrix grain size distribution. To better understand the internal structure of the analysed ceramic matrix composite material, the experimental study used scanning electron microscopy for microstructure and porosity observation. The tested tubes will be used as liners in an oxy-combustion chamber in future studies. The experiments obtained new and interesting results regarding the water permeability of the ceramic matrix composite with different structural parameters. It was also observed that, as with some porous materials, the permeability of ceramic matrix composites decreases with time as more and more liquid is pressed through it.

A hyperelastic approach for modeling the membrane behavior in finite element forming simulation of unidirectional non-crimp fabrics (UD-NCF)

Unidirectional non-crimp fabrics (UD-NCFs) are highly suitable for high-performance components due to their excellent lightweight potential. However, during forming they are prone to wrinkling and gapping compared to woven or biaxial textiles. Macroscopic simulation models can be used to efficiently predict these effects as well as the global forming behavior for complex geometries. Therefore, a new hyperelastic membrane model is proposed to describe the typical deformation of UD-NCFs based on superimposed shear, transverse tension and compression perpendicular to the fiber rovings. The model is parameterized using the forces and different ratios of superimposed strains obtained in experimental off-axis-tension-tests at bias angles of 30°, 45°and 60°. The resulting approach is validated by forming simulations of a hemisphere and tetrahedron geometry in different configurations and quantitative comparison to experimental tests. The model accurately predicts the forming behavior of UD-NCF with a good agreement of the global deformation behavior and local strains.

VERIFICATION OF LAMINATE COMPOSITEPLATE SIMULATION UNDER COMBINED LOADINGS THERMALSTRESSES

This study deals with thermal cyclic loading phenomena of plates which were fabricated from composite materials (woven roving fiber glass + polyester) were exposed to (75 C°) temperature gradient thermal shock for ten times in different stage of conditioning times due to the effect of thermal fatigue using the method of Levy solution and compared these results with both results from experimental published work and (ANSYS Ver. 9) program. A composite laminate plate with fiber volume fraction (υf =25.076%) is selected in this study and applying the combined loadings like bending moment (Mo), and in-plane force (Nxx) beside the effect of thermal fatigue. It involves multi theoretical and finite element fields; but the theoretical one contains the derived equation of stresses distribution and evaluating the normal deflection of a middle point for dynamic analysis applying different boundary conditions for heating and cooling. The main present numerical results for a composite plate with (80%) fiber volume fraction claim that the relative reduction in normal deflection and dynamic load factor are (78.593%) and (9.421%) during cooling to (-15 respectively.

Alkali resistance prediction and degradation mechanism of basalt fiber: Integrated with artificial neural network machine learning model

Basalt fiber is commonly regarded as an alkaline corrosion-resistant material, capable of being transformed into various products (such as basalt fiber roving, chopped yarn and composite reinforcement). However, the main composition of the basalt fiber network skeleton consists of Si ∼ O bonds, which can still react with ∼OH in the alkaline environment. Nevertheless, there are differing viewpoints on the alkaline corrosion of basalt fibers within literatures. Therefore, this study aims to select three representative types of basalt fibers and compare them with two alkali-resistant glass fibers and one regular glass fiber. The attenuation mechanism of basalt fibers were investigated through orthogonal experiments, practical application scenarios and microscopic characterization methods. Additionally, we employed the Weibull model to analyze failure probabilities after erosion on basalt fibers while also applying a machine learning artificial neural network (ANN) model for predicting their alkali resistance. The results indicated that the tensile strength of basalt fiber tended to decrease and the alkali resistance of basalt fiber between alkali-resistant glass fiber and regular glass fiber in four alkaline solutions. The Weibull model also confirms that erosion increases failure probability of basalt fiber and glass fiber. Moreover, Si ∼ O, which forms the network reacted with OH-, resulting in a reduction in surface Si and Al elements content. It became possible to predict the alkali resistance of basalt fiber accurately by establishing an ANN model. Our study provide a theoretical foundation for predicting the lifespan of basalt fibers under corrosive conditions while offering guidance for enhancing their alkali resistance.

Tannins as Biobased Molecules for Surface Treatments of Flax Wrapped Rovings for Epoxy/Flax Fabrics Biocomposites: Influence on Mechanical Properties through a Multi-Scale Approach

The present study examined the effect of biobased molecules grafted onto wrapped flax rovings on the mechanical properties of fabrics designed for epoxy-based biocomposites, aiming to optimize fiber/matrix adhesion. Biobased solutions, such as tannins from quebracho, were used to treat wrapped flax rovings in comparison to a non-biobased aminosilane solution used as a reference. The chemical treatment is performed using an innovative lab-scale impregnation line. The influence of the solution concentration has been investigated. SEM-EDX and FT-IR confirmed the grafting efficiency of molecules on wrapped rovings. Plain and 5-harness satin fabrics were then manufactured at lab scale with the resulting functionalized rovings. Tensile tests were carried out on rovings and on fabrics. A concentration of 1% silane is sufficient to improve the mechanical properties of rovings and fabrics. The addition of NaOH to tannins strengthens flax fiber rovings more than tannins alone, and the weave pattern influences mechanical performance.

Strength analysis of marine biaxial warp-knitted glass fabrics as composite laminations for ship material

Abstract Fiberglass-reinforced plastics (FRP) composite materials for ships that are widely used are marine-grade unsaturated polyester resin matrix and combimat fiber, a combination of marine-grade chopped strand mat (CSM) and woven roving (WR) fibers. Although less popular than marine CSM–WR, marine biaxial warp-knitted glass fabrics have the potential to be applied as fiber laminates for ship hull materials. A comparative study of tensile and bending strength between marine CSM–WR composite and marine CSM–biaxial composite had been conducted. All composites met the criteria of the Indonesian Classification Bureau. Specifically, the CSM–biaxial had higher tensile and flexural strength with fewer laminations than the CSM–WR. Laminate type II had the highest average normalized tensile and flexural strength, 186.1 and 319.2 MPa. A layer of biaxial fiberglass had a very significant effect on tensile and flexural strength. Besides its strength, fewer type II laminations can speed up the production process of FRP ship hulls. Furthermore, the CSM–biaxial composite had relatively high normalized flexural strength compared to other references. However, the normalized tensile strength achieved in this study was at an intermediate level compared to other references.

First Conclusions on Damage Behaviour of Recycled Carbon Staple Fibre Yarn Using X-ray and Acoustic Emission Techniques.

This paper presents the first results on the characterisation of the damage behaviour of recycled carbon fibre (rCF) rovings manufactured into unidirectionally (UD) reinforced plates. In the first step, the mechanical properties of several material combinations were determined by mechanical tests (tensile, flexural, compression). This proves the usability of the material for load-bearing structures. For example, a tensile modulus of up to 80 GPa and a tensile strength of 800 MPa were measured. Subsequently, the fracture surface was analysed by scanning electron microscopy (SEM) to characterise the fibre-matrix adhesion and to obtain first indications of possible failure mechanisms. Despite the high mechanical properties, poor fibre-matrix adhesion was found for all matrix systems. In situ X-ray microscopy tests were then performed on smaller specimens under predefined load levels as transverse tensile and bending tests. The results provide further predictions of the failure behaviour and can be compared to the previous test results. The three-dimensional scan reconstruction results were used to visualise the failure behaviour of the staple fibres in order to detect fibre pull-out and fibre or inter-fibre failure and to draw initial conclusions about the damage behaviour in comparison to conventional fibre composites. In particular, a benign failure behaviour in the transverse tensile test was demonstrated with this procedure. In addition, first concepts and tests for the integration of AE analysis into the in situ setup of the X-ray microscope are presented.

Repair of fire-damaged RC square columns with CFRP textile-reinforced ECC matrix

Fiber-reinforced polymer (FRP) textile reinforced engineered cementitious composite (ECC) matrix (TRE for short) is a newly developed composite system with great potential for the strengthening and life extension of damaged reinforced concrete (RC) columns after fire exposure. It combines the advantages of the lightweight and high strength of FRP textile and the ultra-high ductility of ECC material. However, there is a lack of research on the use of the TRE system to strengthen fire-damaged RC columns. This paper presents an experimental study on the axial compressive behavior of fire-damaged square RC columns strengthened with the TRE system. A total of 13 specimens were prepared and tested under axial compression. The test variables included the fire-exposure time (2 h or 3 h) used to produce the initial pre-damage of RC columns, the type of cementitious matrix (ECC or mortar), the number of TRE layers (2 layers or 3 layers), and the thickness of the concrete cover (20 mm or 40 mm). The failure modes, load capacity, secant stiffness, ultimate displacement, load–displacement curves of the specimens and the hoop tensile strains in the outermost layer of the CFRP textiles were investigated and discussed. The typical failure mode of the strengthened specimens was characterized by tensile rupture of the fiber rovings bridging the main crack in the strengthening jacket. The results showed that the use of the TRE system could significantly increase the load capacity, secant stiffness and ultimate displacement of fire-damaged RC columns. Depending on the design parameters, the enhancement percentages in the load capacity varied between 18% and 126%.

Approaching Polycarbonate as an LFT-D Material: Processing and Mechanical Properties.

Long-fiber thermoplastic (LFT) materials compounded via the direct LFT (LFT-D) process are very versatile composites in which polymers and continuous reinforcement fiber can be combined in almost any way. Polycarbonate (PC) as an amorphous thermoplastic matrix system reinforced with glass fibers (GFs) is a promising addition regarding the current development needs, for example battery enclosures for electromobility. Two approaches to the processing and compression molding of PC GF LFT-D materials with various parameter combinations of screw speed and fiber rovings are presented. The resulting fiber lengths averaged around 0.5 mm for all settings. The tensile, bending, Charpy, and impact properties were characterized and discussed in detail. Special attention to the characteristic charge and flow area formed by compression molding of LFT-D materials, as well as sample orientation was given. The tensile modulus was 10 GPa, while the strength surpassed 125 MPa. The flexural modulus can reach up to 11 GPa, and the flexural strength reached up to 216 MPa. PC GF LFT-D is a viable addition to the LFT-D process, exhibiting good mechanical properties and stable processability.

Placement defects in thermoset‐impregnated rovings deposited along curved paths

AbstractWet Fiber Placement (WFP) is a novel process for manufacturing complex shaped parts from continuous fiber‐reinforced polymers without semi‐finished products. Here, dry fiber bundles (rovings) are in‐line impregnated with a thermoset resin, followed by almost tension‐free deposition. The freshly impregnated and limp rovings allow for placement in radii. Due to the lack of compression in deposition, subsequent consolidation, for example, via vacuum bagging, is required. However, this consolidation cannot compensate for defects already present in the deposited lay‐up as they will typically occur when depositing rovings along curved paths. In this study, we deposited two carbon fiber rovings in radii between 5 and 2000 mm by WFP. The occurring defects were visually evaluated. Three main defects were observed: Fiber waviness, up‐folding and twists. The extent of the defects was evaluated using image analysis techniques. Results show, that up‐folding and twists are dominant for radii <100 mm, while for greater radii fiber waviness is the main defect. Up‐folding and twists almost completely disappear for radii >500 mm, but a slight waviness is still observed. However, the effect of fiber waviness on the longitudinal stiffness is estimated to be small for radii >500 mm and perhaps acceptable for some applications.

Mechanical properties of extruded continuous glass fiber reinforced wood Particle/HDPE composites: Effects of glass bundle tex and arrangement

Mechanical properties considerably reduce in wood-plastic composites (WPCs) due to the use of wood particles, so the structural applications of these composites are scarce. Thus, embedding continuous fibers is considered the most reliable method for increasing mechanical properties, although there are still challenges in employing this method on a large scale. In this study, an elaborated, special modular die with the capability of adjusting 14 rovings of continuous fibers was designed, manufactured, and implemented to simultaneously embed continuous glass fibers into the extruded WPC profile. More precisely, it was aimed to investigate the arrangement of fiber rovings into the desired positions in a WPC profile of 70 wt% wood content. Also, the effect of the glass bundle tex (at three level, 1200,2400 and 4800) and the fiber position (at four levels, 0, 2, 4, and 6 mm of relative movement of the guides) on the mechanical properties of WPCs was evaluated. According to the results, the flexural strength of reinforced specimens for 1200, 2400, and 4800 texes increased by 85.8, 107, and 159.7%, respectively, compared with the non-reinforced composite. Theoretical values were calculated and compared with experimental outcomes. Based on the results, The failure mode was non-catastrophic, which means the specimens were able to carry partial loading; a desirable characteristic for the structural applications.

The Effect of Glass Fiber Storage Time on the Mechanical Response of Polymer Composite.

The growing demand for polymer composites and their widespread use is inevitably accompanied by the need to know their degradation behavior over a sufficiently long period of time. This study focuses on commercial glass fiber rovings, which were stored in the indoor environment for up to 11 years. Fibers with different storage times, from fresh up to the oldest, were used to produce unidirectional fiber-reinforced polyester composites that were characterized to determine their shear and flexural properties dependent on fiber storage time. A significant decrease in shear strength was observed throughout the aging of the fibers, down to a decrease of 33% for the oldest fibers. An important finding, however, was that the significant decrease in shear strength was only partially reflected in the flexural strength, which corresponded to a decrease of 18% for the oldest fibers at consistent flexural modulus.

Effect of Stacking Sequence on Long-Term Creep Performance of Pultruded GFRP Composites.

Pultruded glass-fibre reinforced polymer (pGFRP) composites are classified as lightweight material, which exhibit high strength-to-weight ratio for structural usage. This composite material has been applied as cross-arm members in transmission towers due to its ability in thermal and electrical insulation. However, the influence of the stacking sequence of pGFRP composite on its mechanical performance has not been fully covered in the literature to explain the long-term durability of the current cross-arm designs. The study expected to evaluate five fiber layers with various stacking sequences in terms of quasi-static and creep tests in a four-point bending mode. The creep test was performed for 1440 h (60 days). These composites were fabricated using the pultrusion process in the form of a square hollow structure. Later, it was cut into composite coupons with various sizes depending on the test conducted. The results showed that nine layers with 0°/45°/0°/−45°/0°/−45°/0°/45°/0° had the ultimate flexural strength. This stacking sequence configurations seemed to be optimally manufactured in continuous roving fibre by alternating between 0° and ±45° fiber orientations. Additionally, the S-9 pGFRP composite sample showed that it had a low-creep deflection with high elastic and apparent creep moduli in 1440 h. In terms of strength reduction factor, this configuration was recorded as the highest. The findings showed that the nine layers of pGFRP composites with alternation of 0° and ±45° fiber orientations were highly suitable for structural application at transmission towers for a long-term operation.

Winding optimization of composite frame by dry fiber rovings

Light-weight fibers reinforced polymer (FRP) composite frames are essential parts of vehicles body in the aerospace and automotive industries. Composite frames are often designed in complex curved 3D geometry through the dry winding process. The winding process of homogeneously wound-up layers of fibers without overlapping and gaps is the main challenge in the fabrication of frames with consistent thickness and acceptable quality. In this study, an industrial robot and winding head are set with a novel optimum process to wind the dry fiber with the specified angles on the frame, to fabricate it with minimum overlapping and local commulation of fibers, yet without gaps. Mathematical models and algorithms are developed to determine the optimal number of simultaneously wounds rovings of fibers in a given layer. In addition, this study addresses the optimum dry winding of curved parts of frames that form a torus geometry. It is shown that the combination of layers of rovings wound successively on the frame at angles of 45°, 90° (i.e. the rovings are laid along with the frame), and −45°, is the most used variant of winding that provides the composite frame with higher strength. Results indicated that an optimal selection of the number and width of the rovings minimizes the overlap of the wound rovings, which saves up to 20% of the utilized fibers. The derived theory is verified on practical tests and experiments, which confirms the development of new suitable procedures to improve the fabrication of FRP composite frames.

Influence of Roller Configuration on the Fiber–Matrix Distribution and Mechanical Properties of Continuously Produced, Mineral-Impregnated Carbon Fibers (MCFs)

The article at hand is envisaged to enumerate significant technological parameters for the successful impregnation of carbon fiber rovings having 50,000 (50 K) filaments, each within a fine-grained, cementitious suspension. Parameters such as the number of rollers as well as the influence of roller deflection and rotation have been investigated and discussed with regard to the quality of the related impregnation and mechanical properties resulting therefrom. Morphological analysis disclosed distinct differences in the fiber matrix distribution, which are particularly reflected in the flexural performance of the mineral-impregnated carbon fibers (MCFs) produced. Moreover, with the best fiber matrix distribution, uniaxial tensile tests on MCFs demonstrated superior tensile strengths, moduli of elasticity, and elongations at rupture.

Damage monitoring of pultruded GFRP composites using wavelet transform of vibration signals

A statistical procedure is presented for monitoring the damage of pultruded specimens using vibration data. Pultruded composite samples are processed by using continuous glass fiber rovings and epoxy matrix. Two different types of damages, a notch in the top layer and a hole at the midsection has been introduced individually in these samples. Vibration signals from healthy and damaged samples are processed using wavelet transform. various time–frequency domain statistical features have been extracted. Also, the time-domain features have been computed from the raw amplitude data. Further, both these features have been exploited to construct the feature space and significant features have been identified by evaluating the contribution rates. Finally, significant feature set is channeled as input to various machine-learning classifiers (deep neural network and support vector machine) and different classification accuracies have been estimated. The capability of these methods to early detect the damage in pultruded composites has been discussed.

Impact damage detection in glass fibre reinforced polymers via electrical capacitance measurements on integrated carbon fibre bundles

Impact damages are critical for fibre reinforced polymers, as they can lead to large delaminations that strongly influence the structural integrity of the components. Therefore, reliable detection of impact damages through structural health monitoring is desired. This paper demonstrates a method for the detection and size estimation of impact damages in glass fibre reinforced polymers using capacitance measurements on integrated carbon fibre bundles. Therefore, individual rovings of glass fibre fabrics are replaced by carbon fibre rovings. After infusion of the laminate, the electrical capacitance is measured between the carbon fibre bundles. Damage in the form of matrix cracks or delaminations results in incorporated air that changes the permittivity of the material and, therefore, can be detected as a capacitance decrease. Considering the magnitude of capacitance decrease, a size estimation of the impacts is possible. Consequently, the presented method can be used for in-situ monitoring of damages in glass fibre reinforced polymers.

Cavitation in thermoplastic melts: New insights into ultrasound-assisted fibre-impregnation

The impregnation of continuous carbon fibre roving with thermoplastic melt is a challenging task due to the high viscosity and surface tension of the melt. A new technique is under development utilizing ultrasonic oscillations within the thermoplastic melt which encloses a fibre roving, to achieve fibre impregnation. Despite ultrasonic processing being very efficient, the specific conditions created in the thermoplastic melt have never been studied before. This study investigated whether cavitation effects could be present during ultrasound-assisted fibre impregnation. The observed acoustic effects allowed us to suggest the possible underlying mechanisms. For the purpose of the study a melt-bath impregnation setup with polylactide was built. To detect the cavitation effects and acoustic parameters a calibrated high-temperature cavitometer was used. The results showed the formation of small cavitation zones in the direct vicinity to the sonotrode tip where the fibre roving would be positioned. Therefore, the occurrence of cavitation was established, and induced effects like shock waves, microjets and microstreaming should be further considered for detailed investigation of the ultrasound-assisted impregnation mechanism.

An energy–momentum couple stress formula for variational-based macroscopic modelings of roving-matrix composites in dynamics

In dynamical systems, fiber-reinforced materials with fiber rovings in a cured matrix material, woven or manufactured by the technology of tailored fiber placement (TFP), for instance, have gained great significance for engineers. Therefore, many finite element simulations are currently in progress during the design of composite parts. But, standard finite element formulations do not take into account dimensions and the direction-dependent flexure and twist stiffness of the rovings. In order to avoid computationally costly mesoscopic finite element models with a discretization of roving-matrix interior boundary interfaces, a macroscopic material model can be derived by introducing micropolar rotation degrees of freedom. Micropolar rotation degrees of freedom allow for a separate constitutive description of the direction-dependent stiffness and inertia of the rovings in the cured matrix material. This continuum model represents an extended continuum formulation with an extended set of balance laws. In its computational setting, the discrete preservation of the complete set of balance laws can be realized by a mixed principle of virtual power in connection with energy–momentum tension stress and couple stress formulas. The guaranteed algorithmic energy–momentum consistency then allows an one-off virtual parameter identification of the macroscopic material constants with the mesoscopic model based on the error of the balance functions. Therefore, a mixed finite element formulation with independent micropolar rotation degrees of freedom is recently published, which are able to simulate dynamical problems by taking into account flexure and twist of the rovings. In this previously published paper, the constitutive laws are at most quadratic such that energy–momentum time integrations are possible without a special couple stress approximation. If a nonlinear strain energy function for flexure and twist of the rovings is considered, a new special couple stress approximation is necessary. Therefore, the present paper completes this mixed finite element formulation with a new couple stress approximation and shows its application by means of that numerical experiments with unidirectional rovings, which are designed for the virtual parameter identification. These fully dynamical examples with large translations, rotations and deformations demonstrate the flexure and twist stiffness of the rovings with roving curvature–twist strain energy functions of Kauderer-type by parameter studies. The complete set of discrete balance laws are satisfied independent of boundary conditions in order to allow the upcoming virtual parameter identification.

A mixed finite element formulation for energy‐momentum time integrations of composites with fiber bending stiffness

AbstractWe aim at dynamic simulations of 3D‐fiber‐reinforced materials in light‐weight structures, which are reinforced by fiber rovings comprised of thousands of filaments. Each roving possesses a separate bending stiffness, which has a large influence on the material behaviour on the macro scale. For the description of this material behavior, we extend a hyperelastic anisotropic Cauchy continuum formulation, which models only the macro‐scopic behaviour of a reinforcement by filaments, by a higher‐order gradient of the deformation mapping as an independent field. The new mixed finite element formulation is based on well‐known mixed finite elements for anisotropic polyconvex material formulations, but include new additional mixed fields concernd with the fiber bending stiffness. As we aim at dynamic long‐term simulations, we apply higher‐order accurate time integrators. Here, we include the new mixed finite element formulation in a variational‐based time finite element method. As numerical examples serve a simple cantilever beam. Here, we first analyze the influence of the fiber bending stiffness.