Carbon Fiber Laminate Research Articles

Behaviour of new LCR and ordinary prestressed concrete railway sleepers under repeated impact loads

Rail operations today have become more difficult due to increasing operating speeds and uninterrupted working conditions. Prestressed railway sleepers especially are susceptible to high-frequency dynamic loads from trains and receive significant damage from these loads. Laminated carbon fiber reinforced polyurethane (L-CFRPU) reinforced concrete railway sleeper models (LCR concrete sleepers), which can be produced more economically and practically than prestressed railway sleepers have higher damping and resonance resistance capabilities. In this study, behaviour of railway sleeper under repeated impact loads was investigated and LCR and ordinary prestressed concrete sleepers were compared. According to the results, new LCR concrete sleepers have higher resistance to repeated impact load and show higher residual strength. In addition, these new concrete sleepers are expected to be beneficial in extending the service life of the railway components, reducing maintenance needs, and reducing harmful effects on the environment.

Investigating the elastic and plastic behavior of I-steel beams by using carbon fiber laminates

In this study, two prepared steel beam specimens subjected to concentrated load were examined. One of those beams is strengthened with using carbon fiber reinforced polymer (CFRP) laminates. The examined specimens have the same physical properties in terms of area section and clear span length. Also, a cover plate was used at the top flange and intermediate stiffeners to reinforce them. Where, this plate was used to ensure the occurrence of failure in the bottom flange. The conducted examination was performed to investigate the influence of using CFRP laminates on various responses such as moment/load–deflection, moment/load–strain, yielding and ultimate load. From the obtained results, the deflection and tensile strain responses for the beam strengthened by CFRP indicated that it is stiffer than those of unstrengthen beam. This difference between the two beams is more obvious in the plastic range. Further, the yielding and ultimate capacities for the strengthened beam were increased as compared with the unstrengthen beam by 71.4% and 52.2%, respectively.

Mechanical and thermal characterization of laminar carbon/epoxy composites modified with magnesium oxide microparticles

AbstractThis paper investigates the effects of magnesium oxide (MgO) microparticles on the mechanical and thermal properties of laminated carbon fiber reinforced polymer composites. The polymer epoxy matrix was modified with 0% (pure), 2 wt%, and 4 wt% MgO fillers. Then the laminar composites were manufactured with the vacuum bag method. The energy absorption capacity and impact strength were determined from the Charpy impact tests, whereas the flexural characteristics were evaluated by conducting three‐point bending experiments. Scanned electron microscopy was used to examine both the dispersion of microparticles and the fracture surface of experimentally tested specimens. Thermal performance of the polymer composites with and without MgO additives was analyzed comparatively by performing the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The decomposition temperatures and glass transition temperatures of the composites were obtained. Approximately 30% increment in impact strength was achieved thanks to the MgO fillers. However, although the flexural strength decreased since the MgO particles caused stress concentration, the flexural modulus was not affected due to the decrease of elongation at break. The TGA and DSC instrumentations showed that the decomposition temperatures increased, and curing behaviors were improved depending upon the MgO content.

Comparison of prestressed concrete railway sleepers and new LCR concrete sleepers with experimental modal analysis

Rail operations today have become more difficult due to increasing operating speeds and decreasing maintenance times. Today’s higher frequency train loads are more detrimental, and prestressed railway sleepers especially are susceptible to these dynamic loads. Laminated carbon fiber reinforced polyurethane (L-CFRPU) reinforced concrete railway sleeper models (LCR concrete sleepers) have the potential to exhibit higher damping and resonance resistance more economically and practically. In this study, experimental modal analysis was performed on a large number of samples produced to understand the damping characteristics of sleepers. According to the results, new LCR concrete sleepers have extremely higher damping ratios of over 50% and are expected to be beneficial in extending the service life of the railway components, reducing maintenance needs and harmful effects on the environment.

Fretting Fatigue Performance of Unidirectional, Laminated Carbon Fibre Reinforced Polymer Straps at Elevated Service Temperature.

The fretting fatigue performance of laminated, unidirectional (UD), pin-loaded, carbon fibre-reinforced polymer (CFRP) straps that can be used as bridge hanger cables was investigated at a sustained service temperature of 60 °C. The aim of this paper is to elucidate the influence of the slightly elevated service temperature on the tensile fatigue performance of CFRP straps. First, steady state thermal tests at ambient temperature and at 60 °C are presented, in order to establish the behaviour of the straps at these temperatures. These results indicated that the static tensile performance of the straps is not affected by the increase in temperature. Subsequently, nine upper stress levels (USLs) between 650 and 1400 MPa were chosen in order to establish the S–N curve at 60 °C (frequency 10 Hz; R = 0.1) and a comparison with an existing S–N curve at ambient temperature was made. In general, the straps fatigue limit was slightly decreased by temperature, up to 750 MPa USL, while, for the higher USLs, the straps performed slightly better as compared with the S–N curve at ambient temperature.

Integrated Fabrication of Novel Inkjet-Printed Silver Nanoparticle Sensors on Carbon Fiber Reinforced Nylon Composites.

Inkjet-printing technology enables the contactless deposition of functional materials such as conductive inks on surfaces, hence reducing contamination and the risk of substrate damage. In printed electronics, inkjet technology offers the significant advantage of controlling the volume of material deposited, and therefore the fine-tuning of the printed geometry, which is crucial for the performance of the final printed electronics. Inkjet printing of functional inks can be used to produce sensors to detect failure of mechanical structures such as carbon fiber reinforced composite (CFRC) components, instead of using attached sensors, which are subject to delamination. Here, silver nanoparticle-based strain sensors were embedded directly in an insulated carbon-fiber laminate by using inkjet printing to achieve an optimized conductive and adhesive geometry, forming a piezoresistive strain sensor. Following the inkjet-printing optimization process, the sensor conductivity and adhesion performance were evaluated. Finally, the sensor was quantified by using a bending rig which applied a pre-determined strain, with the response indicating an accurate sensitivity as the resistance increased with an increased strain. The ability to embed the sensor directly on the CFRC prevents the use of interfacial adhesives which is the main source of failure due to delamination.

Land-based wind turbines with flexible rail-transportable blades – Part 1: Conceptual design and aeroservoelastic performance

Abstract. This work investigates the conceptual design and the aeroservoelastic performance of land-based wind turbines whose blades can be transported on rail via controlled bending. The turbines have a nameplate power of 5 MW and a rotor diameter of 206 m, and they aim to represent the next generation of land-based machines. Three upwind designs and two downwind designs are presented, combining different design goals together with conventional glass and pultruded carbon fiber laminates in the spar caps. One of the five blade designs is segmented and serves as a benchmark to the state of the art in industry. The results show that controlled flexing requires a reduction in the flapwise stiffness of the blades, but it represents a promising pathway for increasing the size of land-based wind turbine rotors. Given the required stiffness, the rotor can be designed either downwind with standard rotor preconing and nacelle uptilt angles or upwind with higher-than-usual angles. A downwind-specific controller is also presented, featuring a cut-out wind speed reduced to 19 m s−1 and a pitch-to-stall shutdown strategy to minimize blade tip deflections toward the tower. The flexible upwind and downwind rotor designs equipped with pultruded carbon fiber spar caps are found to generate the lowest levelized cost of energy, 2.9 % and 1.3 %, respectively, less than the segmented design. The paper concludes with several recommendations for future work in the area of large flexible wind turbine rotors.

Effects of tangential supersonic airflow on the laser ablation of laminated CFRP

Ablation behaviors of laminated carbon fiber reinforced plastics (CFRP) subjected to intense continuous wave laser in the supersonic wind tunnel are investigated experimentally. Comparable laser ablation tests in other environments, i.e., static air, static nitrogen and open airflow, are also carried out. Laser ablation rate in the supersonic wind tunnel is significantly larger than those of the other environments, in particular, at least twice of that in an open tangential airflow condition. The ablation morphology can be classified into two regions, coupled ablation zone (CAZ) and downstream affected zone (DAZ). Coupled thermal-fluid-solid analysis including thermochemical ablation and thermomechanical erosion models reveals that the contribution of each laser mechanisms is distinctive at the different positions of the laser ablation pit.

An All-Solid-State Coaxial Structural Battery Using Sodium-Based Electrolyte.

The transition to a sustainable society is paramount and requires the electrification of vehicles, the grid, industry, data banks, wearables, and IoT. Here, we show an all-solid-state structural battery where a Na+-based ferroelectric glass electrolyte is combined with metallic electrodes/current collectors (no traditional cathode present at fabrication) and thin-ply carbon-fiber laminates to obtain a coaxial multifunctional beam. This new concept aims to optimize the volume of any hollow beam-like structure by integrating an electrochemical system capable of both harvesting thermal and storing electrical energy while improving its mechanical performance. The coaxial cell is a coaxial cable where the dielectric is ferroelectric. The electrochemical results demonstrated the capability of performing three-minute charges to one-day discharges (70 cycles) and long-lasting discharges (>40 days at 1 mA) showing an energy density of 56.2 Wh·L−1 and specific energy of 38.0 Wh·kg−1, including the whole volume and weight of the structural cell. This is the highest specific energy among safe structural cells, while no Na+-based structural cells were found in the literature. The mechanical tests, instead, highlighted the coaxial cell capabilities to withstand severe inelastic deformation without compromising its functionalities, while increasing the flexural strength of the hosting structure. Moreover, the absence of alkali metals and liquid electrolytes together with its enhanced thermal properties makes this coaxial structural battery a valid and safe alternative as an energy reservoir for all the applications where traditional lithium-ion batteries are not suitable.

Experimental and Finite Element Investigation of Laminated Carbon Fiber Reinforced Polymer Reinforced Railway Sleepers

Günümüz demiryolu işletmeciliğinde artan hız ve aralıksız işletim koşulları sonucunda, daha düşük bakım gerektiren çözümler mecburiyet halini almıştır. Bu çalışmada, en önemli demiryolu yapı elemanlarından biri olan traversler ele alınmıştır. Klasik betonarme traverslerin literatürde geçen çeşitli sorunlarına değinildikten sonra bu sorunların kaynağında çözümlenmesi adına mevcut çelik donatılar yerine karbon fiber takviyeli polimerlerin (carbon fiber reinforced polymers, CFRP) kullanımı araştırılmıştır. CFRP donatı olarak da geleneksel dairesel donatı geometrisi yerine çok daha düşük maliyetli lamine form kullanılmıştır. Üretilen prototiplerde yapılan TS EN 13230-3 statik eğilme testleri ve detaylı ANSYS sonlu eleman analizlerine göre uzun ve verimli servis ömrü açısından oldukça olumlu sonuçlar elde edilmiştir.

Carbon/basalt hybrid composite bolted joint for improved bearing performance and cost efficiency

In this study, the bearing performance and cost efficiency of single-lap, single-bolt joint of carbon/basalt hybrid composite were assessed. Two non-hybrid laminate joints (pure basalt fiber and carbon fiber laminate joints), and four hybrid laminate joints (two with sandwich-like stacking sequences and two with non-sandwich-like stacking sequences) were fabricated using a vacuum-assisted resin transfer molding process. In comparison to pure carbon-based joints, the hybrid arrangement of basalt layers sandwiched between carbon layers demonstrated improved mechanical performance (23.4% increase in energy absorption and 4.7% increase in ultimate load) while saving 45% of the cost. The surface morphology of damaged specimens was studied by scanning electron microscopy (SEM) at various stages of the loading process. SEM imaging revealed that the proposed hybrid scheme exhibited shear failure, in contrast to all other hybrid designs, which showed interlaminar failure. This study exhibited a better hybrid laminate joint in terms of performance and cost efficiency; which encourages the use of composites in mid/low-end load-bearing applications.

Strengthening Reinforced Concrete Beams with Carbon Fiber Laminate Mounted in a U-Shape for Static and Vibration Purposes

Strengthening Reinforced Concrete Beams with Carbon Fiber Laminate Mounted in a U-Shape for Static and Vibration Purposes

Understanding the Reinforcement of Graphene in Poly(Ether Ether Ketone)/Carbon Fibre Laminates.

PEEK appears as an excellent candidate to substitute epoxy resins in carbon fibre laminates for high-performance aeronautical applications. The optimization of the properties and, in particular, of the transition region between the fibres and the matrix appear as a major issue prior to serial production. Graphene, modified with two compatibilizers, has been incorporated in the polymer layer with the purpose of imparting additional functionalities and enhancing the matrix-fibre interaction. It is found that both carbon fibres and modified graphene significantly influence the crystallization behaviour and smaller, and/or more imperfect crystals appear while the degree of crystallinity decreases. Despite this, nanoindentation studies show that the PEEK layer exhibits significant modulus improvements (≈30%) for 5 wt.% of graphene. Most importantly, the study of the local mechanical properties by nanoindentation mapping allows the identification of remarkably high modulus values close to the carbon fibre front. Such a relevant mechanical enhancement can be associated with the accumulation of graphene platelets at the polymer–fibre boundary, as revealed by electron microscopy studies. The results offer a feasible route for interlaminar mechanical improvement based on the higher density of graphene platelets at the fibre front that should promote interfacial interactions. Concerning electrical conductivity, a large anisotropy was found for all laminates, and values in the range ~10−4 S/cm were found for the through-thickness arrangement as a consequence of the good consolidation of the laminates.

Thermomechanical analysis of riveted carbon fiber laminates for aerospace applications

AbstractExperimental fatigue tests performed on riveted carbon fiber laminates showed that the specimens, after some thousands of cycles, heated up, reaching around the rivet holes high temperatures. These temperatures if not properly controlled could be detrimental for the joint health. In order to understand the relative importance of all the mechanical and geometric parameters involved in the joint manufacturing, a numerical model of the joined carbon fiber laminates was developed using a commercial finite elements code. A simplified analytical model of heat transfer was then used to simulate the rivets thermal behavior under the assigned operating conditions: this model allowed comparisons with finite elements and can be used for simple thermal simulations. The numerical and analytical results were found in a good agreement with the available experimental results. The present research conclusions can be used for drawing better design rules in the definition of riveted carbon fiber laminates.

Effect of compression and tension types of concentrated edge loads on buckling and vibration behavior of interlaminar hybrid fibre metal laminates

The present study deals with the numerical investigation on the buckling and vibration behaviour of interlayer hybrid fibre metal laminates (HFMLs) subjected to different types of concentrated edge compression and tension loads. The term interlayer hybrid represents carbon and glass fibre laminates are sandwiched in between aluminum face sheets. Totally six different hybrid configurations are taken into consideration separately for cross-ply and angle-ply layup schemes. To serve this purpose a finite element code using MATLAB is developed to examine the effects of hybrid configuration, aspect ratio, fiber orientation, type of loading and boundary conditions have been considered to study the buckling responses of HFMLs. The plate is modelled by using 9-noded heterosis elements by considering the effect of shear deformation and rotary inertia. It is revealed from the investigation that the hybrid configurations and loading conditions significantly affect the buckling and vibration characteristics of HFMLs.

Impedance models for single and two degree of freedom linings and correlation with grazing flow duct testing

Presented here is the development of a predictive model for impedance of single-degree-of-freedom (SDOF) and two-degree-of-freedom (2DOF) acoustic linings that is suitable for the design stage of suppression of inlet noise for turbo-fan engines. It is required that over a probable range of lining physical parameters and operating conditions the impedance spectrum is predicted with accuracy sufficient to support a lining design process and assessment of achievable attenuation. The starting point is a published impedance model for SDOF linings that primarily focuses on the transfer impedance of conventional and micro-perforate face sheets with grazing flow. This is expanded here to include 2DOF linings, introducing new issues related to transfer impedance of the inserted septum. Problems addressed are related to the septum insertion process that can change thickness, hole diameter and open area ratio of the uninstalled septum, and introduce blockage. Required empiricism is discussed and models for face sheet and septum-in-core transfer impedance are derived, applicable to a specific range of sheet thickness, hole diameter, and open area ratio. Manufacturing processes considered are mechanical drilling in the case of the carbon fiber laminate face sheet that is conventional perforate, and laser drilling in the case of the epoxy film micro-perforate septum material. Benchmarking is carried out by comparison of acoustic field predictions, using the proposed lining model in an FEM propagation code, with measured data from a grazing flow duct facility. Test samples include SDOF and 2DOF linings, including cases with three segments, each with distinct physical properties. Example results of comparisons are shown to highlight the fidelity of the impedance model over a frequency range compatible with the grazing flow duct geometry.

On the source of the thermoelastic response from orthotropic fibre reinforced composite laminates

In thermoelastic stress analysis (TSA) of orthotropic laminated polymer composites, heat transfer influences the measured stress induced temperature change, or ‘thermoelastic response’. The composite constituents, including different fibre types, fibre geometry, ply thickness and resin systems, in combination with the manufacturing process means that, even for nominally identical materials, different conditions are generated for heat transfer. Hence, definitively identifying the ‘source’ of the thermoelastic response for a general composite laminate has remained elusive. A procedure based on the simultaneous application of digital image correlation (DIC) and TSA is devised that enables the source of the thermoelastic response to be established categorically. In glass fibre laminates, it is shown that heat conduction cannot take place so the thermoelastic response emanates from the surface resin rich layer. In similar carbon fibre laminates, adiabatic conditions are only met at higher frequencies with the response emanating from the orthotropic surface ply.

Recovery and reuse of carbon fibre and acrylic resin from thermoplastic composites used in marine application

The development of new sustainable routes towards better environmental footprint of composites for marine boatbuilding is motivated by the absence of eco-friendly and economically viable recycling techniques to deal with growing end-of-life thermoset boats waste and increasing restrictive legislation. Thermoplastic composites may offer the possibility to recover raw materials from retired parts, which could have a substantial environmental and economic benefit. This study investigates the feasibility of recovery and reuse of both reinforcement and matrix from a carbon fibre reinforced thermoplastic Elium composite. An original pyrolysis process allowed the depolymerisation of the acrylic matrix and recovery of clean carbon fibres and matrix monomer. Distillation was used to purify the monomer from impurities and a recycled Elium resin was synthesized and reused as matrix with long and aligned recycled carbon fibre reinforcement. The study of the morphological and composition differences at fibre scale resulted in concluding that sizing has been decomposed during depolymerisation process and only small traces of polymer were left on fibre surface. Virgin and recycled resin reinforced with carbon fibre laminates were produced by resin infusion. While tensile modulus, strength and strain at break were nearly unchanged, interlaminar shear strength results showed enhanced fibre-matrix interphase bonding. Dynamic mechanical analysis confirmed the good quality of recovered carbon fibres as well as similar virgin and re-polymerised resin properties. The new composite made from both recycled fibre and matrix could be used in the same application field.

Review of THz-based semiconductor assurance

Terahertz radiation for inspection and fault detection has been of interest for the semiconductor industry since the first generation and detection of THz signals. Until recent hardware advances, THz systems lacked the signal quality and reliability for use as an effective nondestructive testing (NDT) method. Incremental advances in THz sources, detectors, and signal processing resulted in the successful applied-industrial use of THz NDT techniques on carbon fiber laminates, automotive coatings, and for detection of counterfeit pharmaceutical tablets. Semiconductor inspection and verification methods ensure the functionality and thereby safety of vital electronics for several critical industries. For this reason, the reliability and verification of a THz NDT method must exceed currently used inspection systems. With recent laboratory access to THz radiation, THz inspection methods are often compared with existing optical, electrical, and volumetric semiconductor verification techniques for their production monitoring and failure analysis viability. This review will cover THz techniques and their applications at the printed circuit board (PCB), integrated circuit (IC), and transistor/gate scales. The THz radiation gap spans between optical and electronic ranges with a millimeter-sized wavelength allowing for adequate penetration of plastic and ceramic and semiconductor materials. THz radiation can be used to determine structural features, electrical signatures in the THz range, and chemical information simultaneously. Cost and environmental limitations restricted the ability for THz NDT semiconductor inspection methods to escape the lab and succeed in the dynamic environment of a semiconductor fabrication environment. Hybridized metrology methods incorporating information from multiple inspection tools are a regime where THz spectral and structural data can be combined with existing methods such as optical, x-ray, or E-beam. THz can be used initially to offer support to the complex failure analysis and verification requirements of the semiconductor industry from nanoscale to macroscale features and components. For THz systems to become independent inspection tools used for semiconductor production monitoring, in the lab or fab, this will require a confident level of statistical process control for THz signal generation, detection, or processing. Applied industrial semiconductor device inspection will likely be a result of a combination of research into THz hardware, reconstruction techniques, and the widespread application of machine learning techniques. Many breakthroughs occurred over the years to enable successful nondestructive characterization and inspection of semiconductor devices from the nanoscale transistors to fully packaged integrated circuits and assembled PCBs.

STATIC TENSILE EXPERIMENT AND NUMERICAL ANALYSIS OF LAMINATED CFRP STRAPS

Pin-loaded laminated carbon fiber reinforced polymer (CFRP) straps are produced by winding unidirectional CFRP tapes around two separated pins, and the load is transferred by the pins. Axial tensile tests were performed to investigate the displacement and strain distributions in the individual layers, the crack propagation and the failure modes. A finite element model was developed and validated by the experimental results. Based on the experimental and numerical results, the effect of critical parameters on the load-bearing and failure mechanisms of the strap were analyzed. The analysis shows that the load transfer efficiency of CFRP straps was decreased by 20% compared to the straight strap. Brittle failure occurred at the intersection between the straight and the curved segments with the development of the delamination and longitudinal cracks. The curvature, strap thickness and friction coefficient had significant influence on the maximum stress of each layer, which always occurred at the intersection between the straight and the curved segments. The load bearing capacity and failure modes were greatly affected by the stress distribution in the curved segment even if the stress level was relatively low.