Carbon Fiber Reinforced Plastic Research Articles

Numerical modeling for shearing of unidirectional carbon fiber reinforced plastic laminates by means of near-net-shape blanking

Structural components made of carbon fiber reinforced plastics (CFRP) exhibit a high degree of lightweight suitability. In order to fulfill geometric and functional requirements, a finishing process step of outer and inner contours is necessary. Near-net-shape blanking processes show potential for economical finishing of CFRP structural components. For the knowledge-based design of a near-net-shape blanking process comparable to fine blanking an understanding of the separation mechanisms during shearing of CFRP laminates is required. Therefore, this paper deals with the development of a finite element (FE) process model for near-net-shape blanking of unidirectional (UD) CFRP laminates with different fiber volume fraction and fiber orientation. Material modeling of the UD CFRP laminates was carried out by means of experimental characterization based on tensile, compression and shear tests. The formulation of the material model was implemented using a VUMAT user subroutine. The application of the blank holder and counter force was realized using a kinematic model based on a VUAMP user subroutine. A validation based on experimental near-net-shape blanking tests will be conducted in the next step.

Analytical Assessment of Composite L Angle Strength Under Internal Fuel Pressure in Composite Wing

The Interspar (IS) box stores the turbine fuel in the composite wing of an Aircraft. The filled fuel is under pressure that induces out-of-plane stresses on all the wing’s structural members around the fuel tank’s boundary. The wing is designed using carbon fiber reinforced plastic (CFRP) with the co-curing of the bottom skin and its stringers along with front and rear spars. A suitable number of cut-outs are made on the top and bottom sides of the IS ribs for the stringer to pass through them. The global finite element analysis showed that the stringer cut-out regions in the IS ribs are highly stressed, as they are subjected to out-of-plane load due to internal fuel pressure, which induces transverse tensile stress in the cut-out region. Resin is the weakest material in the composite laminate, but it has to resist the high-stress component due to out-of-plane loads. The top and bottom flanges of the ‘C’ section IS ribs geometrically form an L angle section with a stringer cut-out made in it. At the L angle location, the IS ribs are critical from both the strength and stiffness point of view. Strength and stiffness at the interface of the fastener joint are essential factors in maintaining the composite wing’s overall structural integrity under internal fuel pressure. The authors adopted the same standalone finite element (FE) modelling approach developed for the Bond Energy Method and carried out appropriate analytical studies to ascertain the safety and structural integrity of the composite wing under internal fuel pressure. This article presents the analytical study carried out on the standalone FE model of an L angle with the stringer cut-out introduced at its appropriate position. The static stress analysis is carried out by enforcing the global displacement on this standalone FE model and extracting three force components in CBAR beam elements representing the resin property in the transverse direction of the composite laminate. The stresses are calculated outside the analysis deck using Excel® spreadsheets. The maximum Normal Stress (σn) in the L angle flange is found to be 13.25 MPa, which is well within the resin or transverse tensile strength of the composite laminate 53 MPa, and the shear stress is found to be 11.10 MPa, which is less than the resin shear strength property of 23 MPa. Hence the study showed that the L angle is safe for carrying internal fuel pressure of 12.5 PSI. The study also showed that the strain and displacement values distribution in the standalone FE model are comparable with that of the global wing box model within the range of (8-10) % and (4-5) % difference, respectively.

Topology optimization for additive manufacturing of CFRP structures

Combining design optimization and additive manufacturing (AM) enables the full exploitation of the potential for heightening the performance of carbon fiber reinforced plastic (CFRP) structures. This study simultaneously conducts topology optimization and fiber path design by employing the radial basis function (RBF) based level set function (LSF). Fiber paths are determined instinctively for the inherent advantages of the LSF, and fiber orientations are parameterized accordingly. Manufacturing drawbacks such as gaps and overlaps can be avoided by introducing a fast-marching method. To verify the effectiveness of the optimization method, three groups of optimized and empirical designs are fabricated by the AM technique, respectively, and the experimental tests are further carried out. Finite element (FE) models are also reconstructed based on the printing schemes, and then the FE simulation is validated by the experimental tests. With the proposed optimization method, stiffnesses for all three groups of the optimal samples are significantly improved compared with the empirical counterparts. The FE modeling technique is capable of reproducing the experimental results. This study paves a new way to develop an integrated framework of optimization, additive manufacturing, experimentation, and validation to deliver high-performance CFRP structures.

Numerical Comparison of Tilt Rotor Propeller Composites Materials of Carbon Fiber-Reinforced Plastic (CFRP), Wood, and Plastic

Numerical Comparison of Tilt Rotor Propeller Composites Materials of Carbon Fiber-Reinforced Plastic (CFRP), Wood, and Plastic

Effect of ultrasonic embossing and welding time on the joint performance of ultrasonically welded short carbon fiber reinforced PEEK

Ultrasonic plastic welding (UPW) is a highly efficient and environmental friendly method that has gained gradually increased attention in joining carbon fiber reinforced thermoplastic (CFRTP). A crucial aspect in UPW of CFRTP is the design of the energy director (ED). This paper employs ultrasonic embossing, a cost-effective way to manufacture ED on the surface of CFRTP sheets. The effect of ultrasonic embossing time and welding time on the joint performance is investigated in terms of microstructure, tensile-shear property, and fracture surface morphology. The results show that the structured surface made by ultrasonic embossing can be used as ED to concentrate welding energy. This process reduces the randomness and dispersion of weld distribution, improves the failure load of welded joints by 30 % compared with the joints made without using ED. The ultrasonic embossing time has a limited influence on the joint failure load. Sound welded joints can be obtained when welding with one structured surface and welding time of 1.5 s.

Complete constitutive model of CFRP including continuous damage in low strain rate compression and temperature generation in high strain rate impact

AbstractThis paper reports a method to construct the complete constitutive model of carbon fiber‐reinforced plastic (CFRP) by distinguishing the strain rate state and modifying the material stiffness. In quasistatic (low strain rate) compression, the initial nonlinear effect caused by the material defects was described by introducing an nonlinear increasing factor. In dynamic (high strain rate) impact, the nonlinear strengthening effect was described by introducing the dynamic amplification factors of stress and strain based on the reference state. Considering the instantaneous temperature rise obtained from the impact work–temperature generation equation and the influence of temperature on modulus and strength, the coupled thermomechanical constitutive models combining the strain rate effect and the temperature effect were established. The user‐defined material subroutines (VUMAT) were developed, and then these constitutive models were verified by finite element analysis (FEA). Finally, the developed material subroutine was applied to predict the impact penetration of CFRP laminates, and the results show that the opening holes, damage and energy dissipation are in good agreement with the reference experiment. This work comprehensively analyzed the construction method of CFRP constitutive models, which would provide a guidance for the coupled thermomechanical behavior under dynamic impact.Highlights An anisotropic continuum mechanical constitutive behavior considering strain rate effect and damage evolution behavior was established. A macroscopic anisotropic constitutive model including the coupled impact temperature generation‐mechanical behavior was established. Combined with the incremental finite element method, the three‐dimensional user‐defined material subroutines (VUMAT) were developed and verified. The thermomechanical impact penetration behaviors of CFRP laminates was predicted, and the stress field, temperature field and failure characteristics were visualized.

Mechanism and Influence Research on the Bending and Torsion Damping of Composite Hollow Tube

The internal damping has a significant influence on the dynamic performance of carbon fiber-reinforced plastic (CFRP) drive shaft. In this paper, the traditional damping strain energy model of composite structures was modified using the reverse off-axis transformation. The damping ratio of CFRP hollow tube pieces is then tested using the vibration method, and the accuracy and efficiency of the modified damping numerical model are verified. Meanwhile, the modified model was proposed to study the damping characteristics and contribution rate of the CFRP hollow tube. The results show the influence law of the laminate parameters on the bending and torsion damping of the CFRP hollow tube. How the strain energy dissipation affects the damping of the CFRP hollow tube is discussed, and the mechanism relationship between the laminate parameters and damping is explored. This study provides theoretical guidance for the design of the bending and torsion damping of CFRP hollow tube.

Recycling of wet carbon fiber-reinforced plastic laminates by thermal decomposition coupled with electrical treatment

The use of carbon fiber-reinforced plastics (CFRPs) produces moisture-absorbing CFRP waste, which is usually recycled via thermal decomposition treatment (TDT). However, the oxygen gas generated during heating can hardly penetrate dense CFRPs, resulting in nonuniform damage to the recovered carbon fibers (rCFs) collected from the outer (oCFs) and inner (iCFs) parts of CFRP waste. Herein, TDT was coupled with electrical treatment (ET) to improve the recycling performance of CFRP laminates waste. The tensile strength of the rCFs measured via the single-fiber tensile tests was analyzed using a two-parameter Weibull distribution. Absorbed water was preferentially evaporated from the laminates by Joule heating during ET, resulting in extensive pore formation. Following TDT, the oCFs and iCFs showed nearly identical average tensile strengths because the pores formed by ET served as efficient diffusion pathways for oxygen gas. The proposed recycling technology may potentially be applied to other types of moisture-absorption waste.

Heat generation mechanisms during induction heating of cross-ply carbon fiber reinforced thermoplastic laminates

Induction welding is considered to be one of the most promising welding technologies for carbon fiber reinforced thermoplastic (CFRTP) composites. However, the uncertainty of heat generation mechanisms presents a challenge to regulating the temperature field uniformity. In this paper, a quantitative calculation method for the induction heating efficiency of various mechanisms was proposed for cross-ply CFRTP laminates. Combining electrical and thermal properties, the cross-ply CF/PEEK and CF/PPS induction heating experiments were designed to explore the quantity ratio of various heat generation mechanisms. The results show that the heat production at the junction is about 106-107 times that of fiber heating. The dielectric loss is dominant mechanism at the junction, and the proportions of heat generated by dielectric loss in CF/PEEK and CF/PPS laminates were 0.6688 and 0.8255, respectively. Furthermore, the temperature prediction model with various stacking sequences was established, showing a good agreement with the experimental temperatures.

Effects on hybridization of interlayer composites and self-reinforced polypropylene

In recent years, there has been increasing attention to develop a high-strength, lightweight composite as a potential substitution for conventional materials in various sectors, whereby most studies have focused on the mechanical performances of fibre-reinforced plastic (FRP) such as carbon, glass and aramid. In contrast, the hybrid composites are less common, though are viewed to have substantial potential in terms of flexibility and capability to merge the benefits of different composites. In this study, five composite designs consisting of several types of woven fibres and self-reinforced polypropylene (SRPP) sheets have been fabricated using the hand lay-up procedure. Several designs are arranged based on the interlayer hybridization mode. The static mechanical properties of the composite designs were examined through the standard tensile and three-point flexural tests. The outcomes attained from the experimental works revealed that carbon fibre-reinforced plastic (CFRP) produced the best tensile characteristics. The CFRP structure displayed 46% higher tensile strength and a 33% greater elastic modulus compared to the CAFRP specimen. Meanwhile, hybrid carbon/aramid fibre-reinforced plastic (CAFRP) pointedly enhanced flexural properties in comparison with single type and other hybrid composites, whereby CAFRP structure outperformed the CFRP structure, exhibiting superior results with variations of 50% and 19% in flexural strength and modulus, respectively. Though the inclusion of SRPP layers in-between the hybrid setup exhibited a decrease in both tensile and flexural strength, but improved the total strain level. The evidence from this study suggests that FRP composites indicate structures of high strength and stiffness but low elongation, whereas SRPP-based composites improve toughness but reduce stiffness characteristics.

Durability of CFRP strengthened RC beam after six years exposure to natural hygrothermal environment with sustained loads

Exploring the durability of Carbon Fiber Reinforced Plastic (CFRP) strengthened concrete structures is a significant focus in the field of civil engineering. The majority of the present durability studies, which investigate the combined effects of external and environmental loading on CFRP-strengthened concrete structures, are conducted in accelerated aging environments. Nevertheless, this method fails to accurately reflect the real service conditions experienced by these structures in natural hygrothermal environments. In this study, a 6-year-long natural exposure experiment is conducted on CFRP-strengthened reinforced concrete (RC) beams under sustained loads. Additionally, the static and fatigue behavior of the exposed beam is investigated through both experimental and theoretical methods. The results indicated that the ultimate load of CFRP-strengthened RC beam remained unchanged after 6 years of natural exposure, as compared to that of non-exposed beams. However, noticeable changes were observed in their fatigue performance. The fatigue life decreased by 30 %, 75 %, and 86 % at loading levels of 0.60, 0.65, and 0.72, respectively. The fatigue limit decreased by 10 % and exhibited a dense distribution of cracks. Meanwhile, a fatigue life prediction model for RC structures strengthened with CFRP after long-term exposure to natural hygrothermal environment was established. In this model, the degradation of the CFRP-concrete interface behavior was considered. Through finite element analysis, two failure modes were predicted: fracture of the main reinforcement and the CFRP-concrete interface debonding failure under fatigue load. The corresponding fatigue life times were calculated. This model agrees well with the experimental findings.

Influence of the thermal expansion on the surface quality of coated and non-coated natural-fiber-reinforced composites

Natural fiber reinforced plastics (NFRP) are increasingly used as a sustainable material alternative to glass or carbon fiber reinforced plastics in lightweight solutions. Visible and/or decorative coated components must meet high surface qualities and defects such as fiber print-through due to different expansion behavior of fiber and matrix are not permitted. Various studies investigate the expansion behavior of NFRP under the influence of temperature and humidity on mechanical properties. In contrast, there are no studies that relate these properties to decoratively coated NFRP and the importance for surface quality. The present study aims to fill this gap using a flax fiber reinforced bio-based epoxy resin (FFRP) manufactured by resin transfer molding process (RTM). The surface roughness and the coefficient of thermal expansion (CTE) were determined as a function of the fiber mass fraction. Further, FFRP and carbon fiber reinforced plastics (CFRP) were decoratively coated and subjected to an alternating climate test. The results showed that reducing the fiber mass fraction of an FFRP to 40 % and using a glass-fiber non-woven on the surface, in combination with 50 % fiber mass fraction, were the most promising methods for reducing roughness in the uncoated state. In addition, the FFRP exhibited an increased CTE longitudinally of 11 ppmK−1 and transversely of 105 ppmK−1 to the fiber direction compared to the CFRP (5 and 79 ppmK−1), along with increased roughness of Ra 0.8 compared to 0.6. The effect of fiber print-through was shown for all variants by the stress in the alternating climate test.

Multi-condition tool wear prediction for milling CFRP base on a novel hybrid monitoring method

In the carbon fiber-reinforced plastic milling process, the high abrasive property of carbon fiber will lead to the rapid growth of tool wear, resulting in poor surface quality of parts. However, due to the signal data distribution discrepancy under different working conditions, addressing the problem of local degradation and low prediction accuracy in tool wear monitoring model is a significant challenge. This paper proposes an entropy criterion deep conditional domain adaptation network, which effectively exploits domain invariant features of the signals and enhances the stability of model training. Furthermore, a novel unsupervised optimization method based on tool wear distribution is proposed, which refines the monitoring results of data-driven models. This approach reduces misclassification of tool wear conditions resulting from defects in data-driven models and interference from the manufacturing process, thereby enhancing the accuracy of the monitoring model. The experimental results show that the hybrid method provides assurance for the accurate construction of tool wear monitoring model under different working conditions.

Comprehensive parametric analyses on the mechanical performance of 3D printed continuous carbon fibre reinforced plastic

This study presents a novel in-house modelling method called “Fibre Path Generator” and comprehensive parametric analyses on the mechanical performance of carbon fibre reinforced plastic (CFRP) with the fibre path along the principal stress direction, using both finite element (FE) simulations and experiments. The reliability of the developed CFRP model is validated through the fabrication of open-hole tensile test specimens using a co-extrusion composite 3D-printer, which demonstrated a highly compatible maximum tensile load with an error less than 3%. A comparative analysis is conducted to assess the mechanical performance of the CFRP specimen with principal stress fibre placement, which result shows that the maximum tensile load achieved is 172.84% higher than a CFRP model with uniaxial fibre placement. Furthermore, comprehensive parametric studies are carried out, varying the carbon fibre location and width-to-depth (w/D) ratio of the open-hole specimen, in order to evaluate the mechanical performance under the tensile loading. This study results provide useful insights to engineers when enhancing the mechanical performance of CFRP composite structures with effective continuous fibre placement.

Effects of fiber orientation and resin-rich layers in carbon fiber reinforced thermoplastics on electromagnetic induction testing

In this study, we evaluated the effects of the fiber orientation and the presence of resin-rich layers on electromagnetic induction testing (EIT) of carbon fiber reinforced thermoplastics (CFRTPs). First, a finite-element analysis was performed to evaluate the distribution and path of the eddy and displacement currents induced in interlaminar conductive and interlaminar non-conductive CFRTP specimens. Second, interlaminar electrically conductive and interlaminar non-electrically conductive specimens of unidirectional CFRTP and cross-ply laminated CFRTP were fabricated using a 3D printer, with control of the number of PA-6 layers and fiber orientation. EIT of the specimens revealed that the presence of resin-rich layers and fiber orientation affected the measured EIT output. The results also indicated that the EIT of CFRTP with resin-rich layers requires penetration of displacement currents between the layers.

CFRP drive shaft damage identification and localization based on FBG sensing network and GWO-BP neural networks

Carbon Fiber Reinforced Plastic (CFRP) has the advantages of light weight, high strength, small coefficient of thermal expansion, good vibration damping performance, etc., the use of its production drive shaft can reduce weight, improve the intrinsic frequency, transmission efficiency and precision, and has been used in helicopters, heavy duty machine tools, wind turbines, ships and other high-end equipment. Once the damage occurs, it will cause adverse effects such as reduction of mechanical efficiency of the system, degradation of transmission system performance, and decrease of reliability and safety. The existing non-destructive testing technology for carbon fiber reinforced plastic has limitations such as inconvenient use, complex equipment, and no real-time online monitoring. To address this problem, this paper adopts Fiber Bragg Gratings (FBG) sensors to obtain real-time strain field data of CFRP drive shaft, and uses the linear and nonlinear mapping ability of Back Propagation Neural Network (BP neural network) to identify and locate the damage of CFRP drive shaft. At the same time, the GWO optimization algorithm is used to optimize the BP neural network to construct a CFRP drive shaft damage identification and localization system based on FBG sensing network and GWO-BP neural network. The experiments show that the CFRP drive shaft damage identification and localization system constructed in this paper can obtain the CFRP drive shaft strain field information in real time and accurately identify the damage and its location.

Study on the interfacial microstructure evolution of aluminum and CFRTP on FSLW joints: influence of pin length

Polymer/metal hybrid lightweight structures are increasingly employed in automotive, aerospace and electronics industries. Friction stir welding (FSW) is applied for the effective welding of metals and thermoplastic materials. For the welding of dissimilar materials, due to the significant property differences, it is hard to achieve high strength welded joints with smooth appearance. In this article, the influence of pin length is studied by experiments for the friction stir lap welding (FSLW) of Al alloy and carbon-fiber-reinforced thermoplastic (CFRTP). Tensile tests, OM, SEM and EBSD are carried out to evaluate the welding performance. Results indicate that the joint with smooth surface topography is obtained at the pin length of 2.5 mm with a peak temperature of 250.3 °C and the CFRTP matrix PEI thermal decomposition temperature residence time of 47.6 s. From OM and SEM micro analysis, the width of the bonding area is 3.02 mm and a thin uniform interaction layer is formed in the joint. EBSD confirms that the Al alloy in the stirring zone is refined after recrystallization. It is difficult to form a stacked layered structure in the bottom of joint, so the property of the joint is improved. The tensile strength is 32.9 MPa, which is 63.1% of CFRTP.

Effect of Special Plating Films on Galvanic Corrosion Behavior between Metal and CFRTP

In this study, electrochemical measurements and observations investigated galvanic corrosion behavior between various metals with or without projection-shaped Ni–Cu alloy plating film and carbon-fiber-reinforced thermoplastic (CFRTP) of corroded areas. Stainless steel, aluminum alloy, and CFRTP plates were prepared. Ni and Ni–Cu alloy electroplating were performed on the stainless steel plate. Electroless zinc plating, Ni, and Ni–Cu alloy electroplating were performed on the aluminum alloy plate. The galvanic current between the metal and CFRTP plates was measured using an electrochemical measurement system. The test solution was 0.06 mol/L NaCl aqueous solution. For Stainless steel/CFRTP, the galvanic current flow was negligible with and without the Ni–Cu alloy plating film. For aluminum alloy/CFRTP without the Ni–Cu alloy plating film, the galvanic current ranged from-80 to-120 μA/cm2 at a test temperature of 60°C. For aluminum alloy with the Ni–Cu alloy plating film, the galvanic current ranged from-60 to-80 μA/cm2. The galvanic current for the aluminum alloy plate with Ni–Cu alloy plating was lower than that of the aluminum alloy plate without Ni–Cu alloy plating film. The result suggests that the formation of the Ni–Cu alloy plating on the aluminum alloy improves corrosion resistance.

Failure analysis and evaluation for cracked concrete beam reinforced with CFRP

With the development of material technology, many kinds of fiber materials have been exploited. In all these fiber materials, carbon fiber reinforced plastic (CFRP) is widely used in civil engineering. First, in this paper the reinforcement performance and failure of cracked concrete beam reinforced with CFRP are studied by digital image correlation method. Secondly, a simple method for the evaluation of reinforcement effect for cracked concrete beam reinforced with CFRP is proposed and verified by experimental results. The reinforcement effect for cracked concrete beam reinforced with CFRP can be evaluated in the service process without specimen damage by this method. Finally, the effects of the bond defect of CFRP on reinforcement effect are studied by this evaluation method. This method plays an important role in the safe application of concrete beams reinforced with CFRP.

A new method of preparing lattice structures of continuous carbon fiber-reinforced thermoplastics

The three-dimensional lattice sandwich structure of composite has attracted extensive attention in the engineering field due to its superior mechanical property and multifunctional designability. Developing technology that can guarantee both production cycle and cost remains challenging. In this work, an innovative forming technology based on 3D printing and hot folding process is presented to fabricate lattice sandwich structures of continuous fiber-reinforced thermoplastics. The prepared lattice sandwich structures show obvious competitiveness and superior material efficiency, which is reflected in high compressive strength (23.55 MPa/(g/cm3)) and specific compressive modulus (457.82 MPa/(g/cm3)). The simplified theoretical model and 3D progressive failure model are carried out to predict the compressive behaviors of the lattice sandwich structures, and the results are consistent with the experimental results. Additionally, the flexibility of the proposed method is demonstrated by fabricating various 3D structures.