Carbon Fiber Direction Research Articles

Simultaneous carbon fiber layer thickness and direction measurement and identification using a novel eddy current sensor and simplified multi-scale 1D-ResNet network

A novel eddy current sensor, featuring a triangular excitation coil and three rectangular receiving coils, is proposed for simultaneously detecting carbon fiber layer thickness and directions in the manufacturing process of carbon fiber reinforced polymer (CFRP) materials. It can disclose various carbon fiber layers and directions based on the signals obtained from the three receiving coils. However, classification of carbon fiber layers and directions proves challenging due to the complexity of signal features resulting from different combinations of carbon fiber layers and directions. To address this issue, we propose the use of a simplified multi-scale 1D-ResNet network. Comparative analysis reveals that our proposed network achieves higher train and validation accuracy compared to single-scale 1D-ResNet networks and different layers 1D-ResNet networks. Furthermore, the proposed simplified network not only achieves high classification accuracy with 100% and 99.7% for carbon fiber layers and directions, respectively, but also requires less training time compared to multi-scale 1D-ResNet networks. The novel eddy current sensor proposed in this study enables accurate recognition of carbon fiber layers and their directional orientation through the implementation of a simplified multi-scale 1D-ResNet network in the manufacturing process of CFRP materials. This innovation significantly enhances the quality of CFRP materials during manufacturing, ensuring their strength aligns with predetermined orientations.

Relationship between the tensile modulus and the thermal conductivity perpendicular and in the fiber direction of PAN-based carbon fibers

A thorough knowledge and understanding of the structure–property relationship between thermal conductivity and C-fiber morphology is important to estimate the behavior of carbon fiber components, especially under thermal loading. In this paper, the thermal conductivities of different carbon fibers with varying tensile modulus were analyzed perpendicular and parallel to the fiber direction. Besides the measurement of carbon fiber reinforced polymers, we also measured the thermal conductivity of single carbon fibers directly. The measurements clearly proved that the thermal conductivity increased with the tensile modulus both in fiber and perpendicular direction. The increase is most pronounced in fiber direction. We ascribed the increase in tensile modules and thermal conductivity to increasing anisotropy resulting from the orientation of graphitic domains and microvoids.Graphical abstract

Improvement of interleaving Aramid pulp micro-fibers on compressive strengths of carbon fiber reinforced polymers with and without impact

Compressive strengths and elastic moduli of Carbon Fiber Reinforced Polymer (CFRP) composites can be noticeably improved by multiple ultra-thin interlays with non-woven Aramid Pulp (AP) micro/nano-fibers. 10-ply CFRP specimens with 0, 2, 4, 6, 8 g/m2 AP were tested under uniaxial compression. Those flexible AP fibers, filling the resin-rich regions and further constructing the fiber bridging at the ply interfaces, can effectively suppress delamination growth and lead to very good improvements both in the compressive strength and the elastic modulus. The CFRP specimen with an optimum interlay thickness has a distinct shear failure mode instead of the typical delamination cracking along the direction of continuous carbon fibers. Compressive Strengths After Impacts (CAI) of 12.35 J were also measured, up to 90% improvement in CAI has been observed. It is concluded those ultra-thin interlays of non-woven AP micro/nano-fibers are beneficial to design and manufacture “high strength” CFRP composites.

Ultraviolet Nanosecond Laser-Ablated Groove Analysis of 2.5D Cf/SiC Composites

The 2.5D Cf/SiC composite is a typical heterogeneous material with the characteristics of anisotropy, which makes it difficult to predict the size and damage removed by the traditional contact removal process. This paper adopted the ultraviolet nanosecond laser to ablate the Cf/SiC composites by considering the heterogeneous structure’s effect. The ablated groove topography and size prediction are effective in revealing the machined quality with predictable groove sizes. The effects of laser processing parameters on the groove morphology and surface thermally affected zone are investigated with the thermal removal mechanism. A regression model is established by considering the scanning times, scanning speed, laser power and pulse width as the main variables. In the regression models, the relative error values are all below 10%. It is revealed that the groove width diminishes with the scanning speed and increases as the laser power increases. However, the influence of the scanning times and pulse width is small, and the overall variation range is within ±10 μm. The results show that the arrangement direction of carbon fibers has an impact on laser processing, especially when the pulse width is 0.25 μs, upon which the opposite change occurs. Carbon fiber grooves are not obvious and are barely observed in the laser processing of the parallel carbon fiber direction, and the grooves are slightly uneven. This study could be helpful in analyzing the grooves of Cf/SiC affected by the laser processing process, which could support the hybrid machining of the Cf/SiC composites.

Improving the damping properties of carbon fiber reinforced polymer composites by interfacial sliding of oriented multilayer graphene oxide

The damping properties of carbon fiber reinforced polymer (CFRP) composites play a critical role in many engineering fields. The purpose of this paper is to investigate how the damping properties of CFRP composites can be improved by interfacial sliding of two-dimensional multilayer graphene oxide (GO). In this work, we show how the energy dissipation ability along the carbon fiber direction is enhanced by oriented GO at carbon fiber/epoxy interface. The damping loss factor of CFRPs is measured by a dynamic mechanical analyzer. The effects of the GO on the damping properties of CFRPs are investigated under different sweep modes (temperature, frequency, and strain). The results show that the deposition of the GO on the surface of the carbon fiber can enhance the damping properties of CFRPs in a wide range of temperature, frequency, and strain domains. Quite significantly, the damping loss factor of CFRPs (0.0345) increases by 113% at a strain of 0.23% and a frequency of 1 Hz. Furthermore, a numerical parametric analysis based on the strain energy method is proposed in ANSYS to obtain the interphase properties of multilayer GO by reference to experimental data. The GO interphase damping parameters can be used to predict the damping properties of multilayer carbon nanomaterials modified composites under different service conditions.

Electric conductivity and surface potential distributions in carbon fiber reinforced composites with different ply orientations

The electric conductivity and surface potential distributions of carbon fiber laminated panels with different ply orientations have been investigated. We found that the unidirectional (UD) lamina has higher conductivity along the carbon fiber direction than the perpendicular direction, and equipotential contours also show different gradients along the two directions. The cross-ply (CP) and quasi-isotropic (QI) laminates have the mixed effects of the UD lamina electric conductivity and ply orientations, while the surface potential distributions mostly depend on the surface lamina direction. The conductivity along the thickness direction depends on each lamina and inter-laminar bonding. A finite element analysis model was also developed to show the effect of ply orientation on potential distribution. The CP and QI laminates with 0° surface ply have uniform potential distributions and isotropic electricity behaviors. The results could be used to monitor damage locations and design electric composite materials.

Thermal dynamic damage of aircraft composite material suffered from lightning channel attachment based on moving mesh method

There is a complex nonlinear dynamic coupling and multi-physical damage between lightning channel and composite material. This paper aims to study the coupling mechanism between lightning channel and composite material. Magneto Hydro Dynamics (MHD) model is established to describe physical characteristics of lightning channel. Moving mesh approach and interface tracking method are applied to deal with the dynamic damage of composites material exposed to lightning channel. This coupling numerical method is validated by a case of aluminum (Al) alloy plate under lightning channel. It is also investigated the current flow, dynamic damage, interaction mechanism of composite laminate during lightning channel attachment. The results reveal that lightning current mainly flows along carbon fiber direction in plane. Current density decreases along the depth direction of composite laminate. Magnetic field contours exhibit a whirlpool shape around the discharge channel. Electromagnetic force is perpendicular to composite laminate surface. Lightning damage morphology of composite laminate exhibits an inverted cone shape. Ablation depth is about 1.57 mm and damage area is about 2080 mm2, which are consistent with experimental results. There exits mutual relationship between lightning damage morphology and lightning channel evolution.

Polyacrylonitrile based carbon fibers: Spinning technology dependent precursor fiber structure and its successive transformation

AbstractIn this study, the effects of different spinning methods including traditional wet and dry‐jet wet spinning, and newly developed dry‐jet gel spinning, on the structures and performances of polyacrylonitrile fibers, as well as the structural evolution during stabilization and carbonization, are compared in detail. The structural differences along radial direction, surface roughness, and chain orientation of carbon fibers are inherited from their precursor fibers, and these factors are determined by spinning technologies and processing conditions. Among all spinning methods, dry‐jet gel spinning could prepare fibers with the best chain orientation, the highest tensile properties, and the lowest surface roughness, which would be favorable for achieving higher mechanical performance. Additionally, for the resultant carbon fibers, the surface modification of dry‐jet gel spun carbon fibers is easier than dry‐jet wet spun carbon fibers, and comparable to wet spun carbon fibers. Overall, dry‐jet gel spinning is promising to make carbon fibers with both excellent tensile properties and good interfacial adhesion with epoxy matrix.

Comparison of Mode Shapes of Carbon-Fiber-Reinforced Plastic Material Considering Carbon Fiber Direction

Previous studies have demonstrated the sensitivity of the dynamic behavior of carbon-fiber-reinforced plastic (CFRP) material over the carbon fiber direction by performing uniaxial excitation tests on a simple specimen. However, the variations in modal parameters (damping coefficient and resonance frequency) over the direction of carbon fiber have been partially explained in previous studies because all modal parameters have only been calculated using the representative summed frequency response function without modal analysis. In this study, the dynamic behavior of CFRP specimens was identified from experimental modal analysis and compared five CFRP specimens (carbon fiber direction: 0°, 30°, 45°, 60°, and 90°) and an isotropic SCS13A specimen using the modal assurance criterion. The first four modes were derived from the SCS13A specimen; they were used as reference modes after verifying with the analysis results from a finite element model. Most of the four mode shapes were found in all CFRP specimens, and the similarity increased when the carbon fiber direction was more than 45°. The anisotropic nature was dominant in three cases of carbon fiber, from 0° to 45°, and the most sensitive case was found in Specimen #3.

Nonlinear elastic response of pan based carbon fiber to tensile loading and relations to microstructure

In this study, wide- and small-angle scattering (WAXS, SAXS) are used to analyze the structure of polyacrylonitrile (PAN) carbon fiber. Wide angle scattering is used to identify lattice parameters such as d-spacings, stacking height of crystalline planes (Lc), average crystallize size (Lc), and various other features (void content, degree of graphitization). Small angle scattering results show orientation and size distributions of pores/amorphous regions. Several analysis techniques were applied to small angle scattering results to ensure accuracy. XRD Data collected is correlated to single fiber mechanical properties and a fiber model is developed. Fiber modulus is heavily related to crystallite dimensions and orientation as well as pore structure. Authors hypothesize that the non-linear elasticity observed in the fiber direction of carbon fibers arises from elastic planar motion within turbostratic carbon. As crystalline regions grow and expand, the lattice structure improves lowering the barriers for (002) quasi-graphene plane motion. This miniscule elastic planar motion can lead to a large nonlinear response to tensile loading especially for high crystallinity carbon fibers and underlying deformation mechanics is addressed considering transverse-isotropy of turbostatic graphite crystals.

Micro-mechanics modeling of compressive strength and elastic modulus enhancements in unidirectional CFRP with aramid pulp micro/nano-fiber interlays

Compressive strength and elastic modulus of unidirectional carbon fiber reinforced polymer (UD-CFRP) have been enhanced experimentally by using soft micro-length Aramid pulp (AP) micro/nano-fiber interlays. This study presents a micro-mechanics model to prove theoretically such enhancements in the compressive strength and elastic modulus of UD-CFRP are possible. The micro-mechanics model recognizes the importance of in-situ formed graded interfacial region between carbon fiber plies generated from the random distribution and out-of-plane movements of micro-length AP micro/nano-fibers. The micro-mechanics model shows that even an areal density of only ~4 g/m2 of AP micro/nano-fibers (with the interlay thickness < 30 μm) is sufficient to generate the enhancements in both compressive strength and elastic modulus along the carbon fiber direction of UD-CFRP. The new micro-buckling or shear failure mechanism has been identified to be responsible for the compressive strength enhancement, instead of local delamination in plain UD-CFRP. The theoretical and experimental findings show interfacial microstructural designs at the carbon fiber ply interface can be critical to the bulk properties of CFRP.

High temperature evolution of the microstructure in the radial direction of PAN-based carbon fibers and its relationship to mechanical properties

High temperature evolution of the microstructure in the radial direction of PAN-based carbon fibers and its relationship to mechanical properties

Temperature-Dependent Dynamic Characteristics of Carbon-Fiber-Reinforced Plastic for Different Spectral Loading Patterns.

The dynamic properties of carbon-fiber-reinforced plastic (CFRP) can be efficiently estimated through a modal damping coefficient and a resonance frequency, and the modal parameters can be calculated using a frequency response function (FRF). The modal parameters used in an CFRP FRF are influenced by the carbon fiber direction, temperature, and spectral loading pattern, as well as the operating conditions. In this study, three parameters—temperature, spectral loading pattern, and carbon fiber direction—were selected as the influential factors for CFRP dynamics, and the sensitivity index formulation was derived from the parameter-dependent FRF of the CFRP structure. The derivatives of the parameter-dependent FRF over the three considered parameters were calculated from the measured modal parameters, and the dynamic sensitivity of the CFRP specimens was explored from the sensitivity index results for five different directional CFRP specimens. The acceleration response of a simple CFRP specimen was obtained via a uniaxial excitation test at temperatures ranging from −8 to 105 °C for the following two spectral loading cases: harmonic and random.

Modal Damping Coefficient Estimation of Carbon-Fiber-Reinforced Plastic Material Considering Temperature Condition.

Excellent mechanical properties of carbon-fiber-reinforced plastic material (CFRP) demonstrates many possibilities in industries using lightweight materials, but unlike isotropic materials, such as iron, aluminum, and magnesium, they show direction-sensitive properties, which makes it difficult to apply for them. The sensitivity of a modal damping coefficient of a CFRP material over the direction of carbon fiber was examined on spectral input patterns in recent research, but the effect of temperature was not considered up to now. To overcome this, uniaxial vibration tests were conducted using five simple specimens with different direction of carbon fiber in a CFRP specimen, the frequency response functions were experimentally determined and the modal damping coefficients were calculated. It was revealed that the resonance point and the modal damping of the specimen changed according to the change in temperature condition. Based on the experimental results, it was demonstrated that the theoretical frequency response function of the carbon composite material is a function of temperature, and it was confirmed that the nonlinear characteristic of the modal damping was the smallest under the 0 degree of direction of carbon fiber.

High temperature evolution of the microstructure in the radial direction of PAN-based carbon fibers and its relationship to mechanical properties

The radial microstructural in carbon fibers is important for their mechanical properties. Microstructures at different locations in the radial direction produced by heat treatments from 1350 to 2400 °C and their relationship to the mechanical properties were investigated by Raman spectroscopy, elemental analysis, X-ray diffraction, high-resolution transmission electron microscopy and mechanical testing. Results indicated that the differences of the shift and full widths at half maxima (FWHM) of the Raman G and D bands at different points in the radial direction from the skin to the core, showed minima while the tensile strength of the fibers was a maximum at 1700 °C heat treatment temperature. The maximum tensile strength of carbon fibers at 1700°C was ascribed to the smallest skin-core variation at this temperature. The FWHM of the G and D bands from the same points in the radial direction decreased with heat treatment temperature, indicating an increased uniformity of the vibration modes of both G and D bands The sizes and the orientation degree of the crystallites increased with heat treatment temperature, leading to an increase of tensile modulus. Non-carbon elements were preferentially released, and crystallites were preferentially grown and orientated in the skin region compared to those in the core due to the preferential heat absorption in the skin, leading to the lower values of FWHM of G and D bands in the skin than in the core. The Raman shift of the G band had a maximum at 1700 °C while that of D band decreased with heat treatment temperature at the same radial points of the fibers. The fact that the release rate of non-carbon elements increased with heat treatment temperature below 1700 °C could be responsible for the increased G band shift below 1700 °C. With a continuous decrease in the non-carbon element content, this effect was lessened and the improvement of the perfection of the graphite structure became dominant above 1700 °C.

Study of Properties of 3D Printed Short Carbon Fiber Composite

The properties of composite materials do not depend only on the properties of raw materials but also other parameters such as volume fraction, geometry, dimension and material distribution etc. Carbon fiber reinforced polymer is one of the top choices of composite material because carbon fiber has light weigh with high tensile strength. For fiber-based composite such as carbon fiber composite, directions of carbon fiber with respect to loading direction could also affect to the strength of composite material under load. In this work, the properties of short carbon fiber-resin composite were investigated (fiber length of 0.2 mm.) with two different fiber orientations, i.e. 0 and 90 degrees to applied load. The 3D printing technique was employed in order to control carbon fiber direction and minimize material loss leading to material cost reduction. It was found that 3D printing technique could control direction of fiber in most case. However, at area with high curvature, the unexpected fiber direction was observed due to post hot process during which material flow was expected. It should also be noted that fiber path during 3D printing process may be very crucial as it could result in low strength local area due to low fiber density. This area could promote stress concentration leading to final fracture.

Transverse and longitudinal flexural properties of unidirectional carbon fiber composites interleaved with hierarchical Aramid pulp micro/nano-fibers

Unidirectional carbon fiber reinforced polymer (UD-CFRP) composites designed for ultimate tensile strength and stiffness along the fiber direction are vulnerable in the transverse direction. In this study, UD-CFRPs were reinforced in the transverse direction using sparsely distributed hierarchical Aramid pulp (AP) micro/nano-fibers between 2 and 8 g per square meter (gsm) per ply interface. Those AP micro/nano-fibers, a few hundred microns in length, effectively formed an ultra-thin interleaving layer around 20 μm in thickness between carbon fiber plies. Flexural properties along and perpendicular to continuous carbon fiber direction were measured under three-point-bending (3-P-B) to determine the toughening effects of AP. Flexural loads in both longitudinal and transverse directions have been enhanced by 30% and over 100% respectively from those randomly distributed AP micro/nano-fibers with diameters varied from a few hundred nanometers to 10 μm. Even slight increase in the elastic modulus of AP-toughened CFRP along the fiber direction was observed. Total fracture energy absorption, initial cracking and final fracture loads were measured and compared, indicating AP micro/nano-fibers have contributed to the high strength, high toughness and high modulus characteristics of AP-interleaved UD-CFRPs. Details on toughening mechanisms were revealed from SEM and cross-section optical microscopy examinations. Comparisons of unreinforced UD-CFRP and AP-toughened UD-CFRP showed the hierarchical AP micro/nano-fibers indeed played an important role in composite microstructure design and property optimization. The ultra-thin interleaved AP veil around 20 μm in thickness can be conveniently incorporated into pre-preg fabrication so that the extra interleaving step can be eliminated, i.e. the toughened pre-pregs can be used as normal pre-pregs in the final composite forming.

Temperature dependence of statistical fatigue strengths for unidirectional carbon fiber reinforced plastics under tension loading

The formulation for time- and temperature-dependent statistical static and fatigue strengths for carbon fiber reinforced plastics laminates is newly proposed based on the physically serious role of resin viscoelasticity as the matrix of carbon fiber reinforced plastics. In this study, this formulation is applied to the tensile strength along the longitudinal direction of unidirectional carbon fiber reinforced plastics constituting the most important data for the reliable design of carbon fiber reinforced plastics structures which are exposed to elevated temperatures for a significant period of their operative life. The statistical distribution of the static and fatigue strengths under tension loading along the longitudinal direction of unidirectional carbon fiber reinforced plastics were measured at various temperatures by using resin-impregnated carbon fiber reinforced plastics strands as specimens. The master curves for the fatigue strength as well as the static strength of carbon fiber reinforced plastics strand were constructed based on the time–temperature superposition principle for the matrix resin viscoelasticity. The long-term fatigue strength of carbon fiber reinforced plastics strand can be predicted by using the master curve of fatigue strength.

Sensitivity Analysis of the Frequency Response Function of Carbon-Fiber-Reinforced Plastic Specimens for Different Direction of Carbon Fiber as Well as Spectral Loading Pattern.

Carbon-fiber-reinforced plastic (CFRP) has been used in many industries owing to its excellent specific-strength characteristics; however, the control of its mechanical properties is difficult owing to the directivity nature of carbon fiber as well as the composition of layered structures. In addition, the damping coefficient of CFRP varies with spectral loading patterns under random and harmonic excitation owing to the high values of damping characteristics compared with conventional steel materials. A scaled sensitivity index was proposed to compare the magnitude of the frequency response function over two parameters of interest: the direction of the carbon fiber and the spectral loading pattern for CFRP specimens. Three specimens with different directions (0°, 45°, and 90°) were prepared and uniaxial excitation testing was conducted for two different spectral loading cases: random and harmonic. The summation of the frequency response was used to calculate the sensitivity index to eliminate the effects of the location of measurement data, and all sensitivity indexes were calculated using the measured responses. Finally, the sensitivity of each CFRP specimen was discussed for two cases, i.e., the direction of carbon fiber and the spectral loading pattern, using the scaled sensitivity index results.

The Optimization of Process Parameters and Characterization of High-Performance CF/PEEK Composites Prepared by Flexible CF/PEEK Plain Weave Fabrics.

Continuous carbon fiber (CF)-reinforced poly (ether ether ketone) (PEEK) composites have excellent mechanical properties, but their processing techniques are limited. Therefore, we promoted a braiding method based on the hybrid fiber method by hot-compacting CF/PEEK plain weave fabrics to solve the problem of difficult wetting between CF and PEEK. Four parameters—melting temperature, molding pressure, crystallization temperature and the resin contents—were investigated for optimized fabrication. After studying the melting range, thermal stability and the contact angle of PEEK under different temperatures, the melting temperature was set at 370 °C. An ultra-depth-of-field 3D microscope was adopted to investigate the effects of molding pressure in the melting stage. The tensile strength or modulus along and perpendicular to the carbon fiber direction and crystallinity under different crystallization temperatures were analyzed. As a result, the sample crystalized at 300 °C showed an excellent tensile properties and crystallinity. The increased mass ratio of PEEK ranging from 50.45% to 59.07% allowed for much stronger interfacial strength; however, the higher resin content can lead to the dispersion of CFs, loss of resin and the formation of defects during processing. Finally, the optimal resin mass content was 59.07%, with a tensile strength of 738.36 ± 14.49 MPa and a flexural strength of 659.68 ± 57.53 MPa. This paper studied the optimized processing parameters to obtain better properties from CF/PEEK plain weave fabrics and to further broaden the specific applications of CF/PEEK composites, demonstrating a new direction for its fabrication.