Woven Carbon Fiber Reinforced Polymer Research Articles

Transverse energy absorption performance of sandwich tubes with various origami foldcores

Nowadays, composite sandwich tubes are extensively utilized in the civil and aerospace industries due to their superior strength-to-weight mechanical properties. Origami-based core offers a large enhancement of the mechanical properties, yet little study research focuses on the effect of various foldcore configurations on the transverse mechanical properties of sandwich tubes, necessitating the design method for applications. This study introduces an innovative approach by incorporating origami into the composite sandwich core to enhance the transverse energy absorption capacity. The quasi-static transverse mechanical properties of carbon fibre-reinforced polymer (CFRP) sandwich tubes with foldcores are studied under three-point bending-like local compression and transverse structural compression. A systematic geometric design framework and numerical modelling technique are provided. By integrating finite element analysis and experiments, the research investigates the effects of various origami foldcore configurations and geometric parameters on transverse energy absorption capacity. The experiment setup is provided by sandwich tubular specimens with a full-diamond configuration as the foldcore. The cylindrical tubes (foldcore) of the sandwich structures were manufactured using four plies [0°]4 of T700 (T300) woven CFRP with the hot press moulding (vacuum bag using female and male moulds) technique respectively. Then, the parametric study and damage mode analysis of eight different foldcore patterns (axial Miura, circumferential Miura, diamond, Kresling, and their curved-creased counterparts) were studied. The results showed the superior energy absorption performance of the sandwich tube with Miura-pattern foldcore over the origami-pattern counterparts, nested tube, and traditional honeycomb sandwich tube with CFRP or aluminium-made cores. Therefore, the structural parameters optimisation of the Miura pattern tube was carried out by the Response Surface method (RSM) and a design strategy for increasing the energy absorption capacity was found. The findings offer guidance for designing high-specific energy absorption tubular structures for future advanced engineering applications.

Cryogenic damage behavior of carbon fiber reinforced polymer composite laminates via fiber-optic acoustic emission

Cryogenic temperatures cause significant changes in the mechanical response and microscopic failure mechanisms of carbon fiber reinforced polymer (CFRP) composites. However, the mechanisms by which cryogenic temperatures affect composites are not yet fully understood due to a lack of adequate in-situ characterization techniques. Herein, the cryogenic damage evolution process of CFRP composites was investigated by constructed fiber-optic acoustic emission (AE) detection system. Tensile damage behavior of woven CFRP composites at 300 K, 153 K and 77 K was evaluated by AE characteristic response and cluster analysis combined with scanning electron microscopy. According to the results, increased damage activity within the composites at cryogenic condition promoted the release of mechanical energy, as well as an increase in the contribution of fiber damage to overall damage, which are the dominant micro-strengthening mechanisms of composite laminates under cryogenic conditions. This study provides a novel explanation for understanding the cryogenic damage behavior of composites.

Permeability and barrier layer properties of a woven carbon fibre polymer composite as battery packaging

Carbon fibre reinforced polymer (CFRP) laminates are used in various studies as Li-ion polymer (LiPo) battery packaging. However, their suitability as a packaging material is not well understood. The present study investigates the liquid absorption (water and lithium bis(trifluoromethanesulfonic)imide (LiTFSI) electrolyte immersion tests) and barrier layer properties (water vapour transmission rate (WVTR) and oxygen transmission rate (OTR) tests) of a 200 gsm woven CFRP laminate to assess its suitability as a battery packaging material. This is the first study to show that prolonged immersion in battery electrolyte does not change the mechanical properties of a woven CFRP laminate. Hence, the CFRP laminate may be suitable for structural battery components, such as current collectors and electrodes. However, CFRP should not be used as battery packaging, as OTR and WVTR values of the CFRP laminate were found to be five and one order of magnitudes higher than typical battery pouch materials (i.e. aluminium foil), respectively.

High-Resolution Ultrasound to Quantify Sub-Surface Wrinkles in a Woven CFRP Laminate.

Carbon fiber reinforced polymer (CFRP) composites are popular materials in the aerospace and automotive industries because of their low weight, high strength, and corrosion resistance. However, wrinkles or geometric distortions in the composite layers significantly reduce their mechanical performance and structural integrity. This paper presents a method for non-destructively extracting the three-dimensional geometry, lamina by lamina, of a laminated composite. A method is introduced for fabricating consistent out-of-plane wrinkled CFRP laminate panels, simulating the in-service wrinkle observed in industries that utilize thick structure composites such as the vertical lift or wind power industries. The individual lamina geometries are extracted from the fabricated coupon with an embedded wrinkle from captured ultrasonic waveforms generated from single-element conventional ultrasonic (UT) scan data. From the extracted waveforms, a method is presented to characterize the wrinkle features within each individual lamina, specifically the spatially varying wrinkle height and intensity for the wrinkle. Parts were fabricated with visibly undetectable wrinkles using a wet layup process and a hot press for curing. Scans were performed in a conventional immersion tank scanning system, and the scan data were analyzed for wrinkle detection and characterization. Extraction of the layers was performed based on tracking the voltage peaks from A-scans in the time domain. Spatial Gaussian averaging was performed to smooth the A-scans, from which the surfaces were extracted for each individual lamina. The extracted winkle surface aligned with the anticipated wrinkle geometry, and a single parameter for quantification of the wrinkle intensity for each lamina is presented.

Detailed Finite Element Models for the Simulation of the Laser Shock Wave Response of 3D Woven Composites

This paper presents a numerical study on the laser shock wave propagation in a 3D woven carbon-fiber-reinforced polymer (CFRP) material by means of detailed and homogenized finite element (FE) models. The aim of this study is to numerically characterize the shock wave response of the 3D woven CFRP in terms of back-face velocity profiles and the induced damage, and to investigate whether the detailed FE models could be effectively replaced by homogenized FE models. The 3D woven geometry was designed using the TexGen 3.13.1 software, while the numerical analyses were executed using the R11.0.0 LS-Dyna explicit FE software. A high-strain-rate behavior was considered for the matrix. The fiber bundles in the detailed models were modeled as a high-fiber-content unidirectional composite laminate, with its mechanical properties calculated by micromechanical equations. A progressive damage material model was applied to both the fiber bundles of the detailed model and the homogenized models. The results of the detailed model reveal a considerable effect of the material’s architecture on the shock wave propagation and sensitivity of the back-face velocity profile to the spot location. Consequently, the homogenized model is not capable of accurately simulating the shock wave response of the 3D woven composite. Moreover, the detailed model predicts matrix cracking in the resin-rich areas and in the bundles with high accuracy, as well as fiber failure. On the contrary, the homogenized model predicts matrix cracking in the same areas and no fiber failure.

High-sensitivity phase imaging eddy current magneto-optical system for carbon fiber reinforced polymers detection

This paper proposed a high-sensitivity phase imaging eddy current magneto-optical (PI-ECMO) system for carbon fiber reinforced polymer (CFRP) defect detection. In contrast to other eddy current-based detection systems, the proposed system employs a fixed position excitation coil while enabling the detection point to move within the detection region. This configuration effectively mitigates the interference caused by the lift-off effect, which is commonly observed in systems with moving excitation coils. Correspondingly, the relationship between the defect characteristics (orientation and position) and the surface vertical magnetic field distribution (amplitude and phase) is studied in detail by theoretical analysis and numerical simulations. Experiments conducted on woven CFRP plates demonstrate that the designed PI-ECMO system is capable of effectively detecting both surface and internal cracks, as well as impact defects. The excitation current is significantly reduced compared with traditional eddy current magneto-optical (ECMO) systems.

Quantification of porosity in composite plates using planar X-ray phase contrast imaging

The application of planar Edge-Illumination X-ray Phase-Contrast imaging (EI-XPCi) for the non-destructive quantification of porosity in carbon fiber reinforced polymer (CFRP) specimens, a significant concern in aerospace applications, was investigated. The method enables fast, planar (2D) scans providing access to large samples. A set of woven CFRP plates with porosity content ranging from 0.7% to 10.7% was examined. In addition to standard X-ray attenuation, EI-XPCi provides differential phase and dark-field signals, sensitive to inhomogeneities and interfaces at scales above and below the system spatial resolution, respectively. The correlation with the porosity content from matrix digestion obtained from the dark-field signal was comparable to that from ultrasonic attenuation. The novel analysis of the standard deviation of differential phase (STDP), sensitive to inhomogeneities above the system resolution (approximately 12 μm), resulted in a very high correlation (R2 = 0.995) with the matrix digestion porosity content, outperforming ultrasonic attenuation measurements.

Experimental and numerical investigation of mechanical behavior of plain woven CFRP composites subjected to three-point bending

The mechanical behavior of plain woven Carbon Fiber-Reinforced Polymer (CFRP) composites under Three-Point Bending (TPB) is investigated via experimental and numerical approaches. Multiscale models, including microscale, mesoscale and macroscale models, have been developed to characterize the TPB strength and damages. Thereinto, Representative Volume Elements (RVEs) of the microscale and mesoscale structures are established to determine the effective properties of carbon-fiber yarn and CFRP composites, respectively. Aimed at accurately and efficiently predicting the TPB behavior, an Equivalent Cross-Ply Laminate (ECPL) cell is proposed to simplify the inherent woven architecture, and the effective properties of the subcell are computed using a local homogenization approach. The macroscale model of the TPB specimen is constructed by a topology structure of ECPL cells to predict the mechanical behavior. The TPB experiments have been performed to validate the multiscale models. Both the experimental and numerical results reveal that delamination mainly appears in the top and bottom interfaces of the CFRP laminates. And matrix cracking and delamination are identified as the significant damage modes during the TPB process. Finally, the quasi-static and dynamic behaviors of plain woven composites are discussed by comparing the results of Low-Velocity Impact (LVI) and TPB simulations.

A New Electrical Resistance Measurement Method of Carbon Fiber-Reinforced Polymer Tubes Based on C⁴D Technique

This work introduces the capacitively coupled contactless conductivity detection ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{C}^{{4}}\text{D}$ </tex-math></inline-formula> ) technique into nondestructive testing (NDT) of carbon fiber-reinforced polymer (CFRP) and proposes a new resistance measurement method of CFRP tubes. The proposed method does not require direct contact between the electrodes and the carbon fiber. Therefore, the electrical resistance of CFRP can be measured without the treatments required by traditional electrical methods that may lead to surface or structural damage. The equivalent circuit model of the new method is established, and the challenges are analyzed. Simulation and experiment are conducted with woven fabric CFRP tubes to verify the feasibility of the proposed method, including the range of workable frequency, the effectiveness of the circuit model, and the capability of damage detection. Research results show that a relatively high working frequency is required to accurately measure the interested resistance and sense the resistance change. By selecting a workable frequency, the effectiveness of the circuit model is verified. Research results indicate that the stray capacitance between the electrodes has little effect on resistance measurement, and the capacitor–resistor–capacitor model is still applicable. Research results also verify the feasibility of the proposed method for damage detection. It is able to sense the resistance change resulted from the damage of CFRP, either the conductivity changes in simulation or actual cutting damage in experiment.

Failure behavior of on-site repaired CFRP laminates

On-site repairs of carbon fiber reinforced polymer (CFRP) composites involve out-of-autoclave curing, which increases the defect density and reduces the mechanical properties. This work aims to understand the strength and the associated failure mechanisms of on-site repaired woven CFRP laminates through experiments and simulations. A series of wet lay-up and prepreg step repaired specimens produced according to standardized aerospace procedures were tested under uniaxial tension. Wet lay-up repair provided a strength recovery of 66%, whereas prepreg repairs maintained 76% of the original strength. Finite element modeling closely predicted the experimentally observed behavior and showed that stress concentrations due to the adhesive-adherent stiffness mismatch are the primary causes of the lowered strength. The findings provide systematic experimental data and an accurate modeling framework to design and implement effective repairs in practice.

Multiscale modeling framework to predict the low-velocity impact and compression after impact behaviors of plain woven CFRP composites

A multiscale modeling framework including microscale, mesoscale and macroscale models, is developed to investigate the low-velocity impact (LVI) and compression after impact (CAI) behaviors of plain woven carbon-fiber-reinforced-polymer (CFRP) composites. Representative volume elements (RVEs) are selected to construct the microscale and mesoscale models, which are further used to compute the effective properties of the carbon-fiber yarn and CFRP composites. An equivalent cross-ply laminate (ECPL) model is used to simplify the woven architecture via a local homogenization approach. The macroscale model of plain woven CFRP composites is established by extending the ECPL model. The LVI and CAI behaviors of CFRP composites are predicted for various impact energy cases. Finally, the corresponding LVI and CAI tests have been performed on plain woven CFRP composites, and the experimental measurements agree well with the numerical simulations, indicating the reliability of the multiscale modeling framework. Importantly, both the experimental and numerical results reveal that the impact damages, especially the intralaminar damages, are prone to cause the decrease of the residual compressive strength of impacted plain woven composites.

Concurrent n-scale modeling for non-orthogonal woven composite

Concurrent analysis of composite materials can provide the interaction among scales for better composite design, analysis, and performance prediction. A data-driven concurrent n-scale modeling approach (\(\text {FExSCA}^\text {n-1}\)) is adopted in this paper for woven composites utilizing a mechanistic reduced order model (ROM) called Self-consistent Clustering Analysis (SCA). We demonstrated this concurrent multiscale modeling theory with a \(\text {FExSCA}^2\) approach to study the 3-scale woven carbon fiber reinforced polymer (CFRP) laminate structure. \(\text {FExSCA}^2\) significantly reduced expensive 3D nested composite representative volume element (RVE) computation for woven and unidirectional (UD) composite structures by developing a material database. The modeling procedure is established by integrating the material database into a woven CFRP structural numerical model, formulating a concurrent 3-scale modeling framework. This framework provides an accurate prediction for the structural performance (e.g., nonlinear structural behavior under tensile load), as well as the woven and UD physics field evolution. The concurrent modeling results are validated against physical tests that link structural performance to the basic material microstructures. The proposed methodology provides a comprehensive predictive modeling procedure applicable to general composite materials aiming to reduce laborious experiments needed.

Electroluminescent strain sensing on carbon fiber reinforced polymer

The present paper demonstrates an inexpensive and less labor-intensive machine vision-based strain and damage visualization technique compared to traditional carbon fiber reinforced polymer material inspection methods. This technique is used to characterize the fracture and failure properties upon progressive axial loading in textile carbon fiber reinforced polymer (CFRP) lamina with non-intrusive smart electroluminescent (EL) integration. The smart EL structure utilizes CFRP's unique conductive and piezoresistive properties to visualize deformation and cracks through brightness change. Two fiber orientations (±45° and 0°/90°) of twill-weave CFRP lamina are fabricated according to a modified ASTM D3039 for linear and fatigue loading in uniaxial mechanical tests to analyze both fiber and matrix-induced EL responses. The EL-strain visualization method is validated with standardized digital image correlation (DIC) utilizing the natural speckling pattern of the EL CFRP lamina. The axial EL-strain results for both static and cyclic loading highly agree with the strain extracted planar conventional DIC strain field on standard and damaged CFRP samples in terms of spatial resolution and sensitivity. This novel strain and damage visualization method aims to be a portable, low-cost, and real-time alternative to non-destructive testing methods commonly used in the composite industry. Instead of periodic checkups, EL architecture allows for real-time strain and damage visualization of composite structure. • Fabrication and tensile testing of strain sensing EL illuminating woven CFRP in [±45°] and [0°/90°] fiber orientations. • Visual damage and strain detection are achieved with EL CFRP structure. • Planar DIC strain fields produced on EL illuminating and conventional airbrushed patterns show strong correspondence. • Variations in piezoresistive and luminance response exhibit correlation with strain.

A novel energy‐based framework for characterizing the strain‐softening behavior of CFRP composites using cyclic loading

AbstractComplex failure modes of carbon fiber reinforced polymer (CFRP) composites create significant challenges for CFRP components' progressive damage analysis (PDA). Though important in PDA, the phenomenological strain‐softening model (SSM) for characterizing the degradation behavior in the fiber‐parallel direction (dominated by fiber breakage) of CFRP is difficult to be constructed by current approaches due to the poor toughness of carbon fibers. The work aims to obtain a refined SSM of plain woven CFRP composites through experimental methods and apply it to the PDA of corresponding components. A novel phenomenological cyclic‐loading‐based strain‐softening model (CLSSM) was proposed based on the theory of equivalent dissipation energy during static and cyclic loading. Firstly, the release behavior of dissipation energy during the cyclic loading process was researched. Secondly, a newly designed search algorithm taking degraded mechanical properties during cyclic loading as input and taking the static strain‐softening curve as output was utilized to build up CLSSM. Thirdly, a three‐point bending test was conducted and a corresponding numerical model was constructed for comparison to verify the proposed model. The entire framework is highly programmatic, and results show that CLSSM is fast for characterizing the strain‐softening behavior, and effectively simulates the progressive failure process of CFRP components.

Tension-Compression Fatigue Induced Stress Concentrations in Woven Composite Laminate

Tension-compression (T-C) fatigue response is one of the important design criteria for carbon-fibre-reinforced polymer (CFRP) material, as well as stress concentration. Hence, the objective of the current study is to investigate and quantify the stress concentration in CFRP dog-bone specimens due to T-C quasi-static and fatigue loadings (with anti-buckling fixtures). Dog-bone specimens with a [(0/90),(45/−45)4]s layup were fabricated using woven CFRP prepregs and their low-cycle fatigue behaviour was studied at two stress ratios (−0.1 &amp; −0.5) and two frequencies (3 Hz &amp; 5 Hz). During testing, strain gauges were mounted at the centre and edge regions of the dog-bone specimens to obtain accurate, real-time strain measurements. The corresponding stresses were calculated using Young’s moduli. The stress concentration at the specimen edges, due to quasi-static tension, was significant compared to quasi-static compression loads. Furthermore, the stress concentration increased with the quasi-static loading within the elastic limit. Similarly, the stress concentration at the specimen edges, due to tensile fatigue loads, was more significant and consistent than due to compressive fatigue loads. Finally, the effects of the stress ratio and loading frequency on the stress concentration were noted to be negligible.

Experiment and Simulation of Impact Response of Woven CFRP Laminates with Different Stacking Angles

The effects of different laying angles on impact resistance and damage types of woven carbon fibre-reinforced polymer (CFRP) laminates were studied. The drop hammer impact test and simulation analysis of woven CFRP laminates at four different velocities were carried out by means of the combination of experiment and explicit finite element analysis. The effect of impact velocity on damage pattern and fracture of woven CFRP laminates with eight layers and four laying angles (0°, 15°, 30°, and 45°) was studied by drop weight impact test, and the damage area of woven CFRP laminates with different laying angles was measured by ultrasonic nondestructive testing method. A user-defined material model was developed based on LS-DYNA to simulate the impact behavior of woven CFRP laminates. A finite element simulation model was established to effectively predict the complex damage evolution of woven CFRP laminates under low-speed impact loading. Its effectiveness was verified by impact response and damage crack pattern. The energy absorption and impact force of the laminated plate increase gradually from 0° to 45° in the laying angle of woven fabric. With the increase of laying angle from 0° to 45°, the length of fracture crack and the damage area increase. The developed model can accurately predict the impact properties of the composites.

In-plane compression response of woven CFRP composite after low-velocity impact: Modelling and experiment

To predict the low-velocity impact (LVI) and compression-after-impact (CAI) behaviour of woven carbon fibre reinforced polymer (CFRP) composites, a finite element (FE) model was developed addressing the inter-laminar and intra-laminar failure of the CFRP composites. First, LVI and CAI experiments were performed to obtain the force-displacement relations, failure modes, microscopic damage and CAI strength of the CFRP laminates, and the experimental results were utilised to validate the present FE model. The LVI and CAI responses of the composites obtained from the FE results agreed well with the experimental ones. Microscopic damage analysis of the CFRP composites after LVI and CAI tests was then conducted by scanning electron microscopy (SEM), indicating the occurrence of three failure modes, i.e. fibre breakage, matrix cracking and delamination, which were addressed in the FE model. Finally, the effects of impactor diameter and impact energy on the impact damage and CAI behaviours were determined using the present FE model, and the damage mechanism was correspondingly discussed.

Effect of no-pressure curing temperature on bending property of 2D-T700/E44 composite

Carbon-fiber-reinforced polymer (CFRP) composites have received extensive attention in aerospace, weapon equipment, communication electronics, transportation and other fields. The improved compression-molding process is one of the most advantageous processes for preparing CFRP composites. It is important to understand the effects of molding process parameters, in particular temperature parameters, on the preparation of an ideal composite. This paper addresses the effect of the no-pressure curing temperature on the two-dimensional woven CFRP (2D-CFRP) bending property of the improved compression-molding process. 2D-T700/E44 composites were prepared under no-pressure curing temperatures of 80, 90, 100, 110, 120 and 130°C. The effect law and influence mechanism of the temperature parameter on the microstructure and bending property of composites were summarized. The results show that excessively high or low no-pressure curing temperatures are unfavorable for the preparation of 2D-T700/E44 composites. When the temperature is 110°C, the impregnation effect of the resin is ideal, and the defects are effectively controlled. The fracture morphology is reasonable, and the performance is greatly improved, so the bending strength reaches 860 MPa.

Research on prediction method of mechanical properties of open-hole laminated plain woven CFRP composites considering drilling-induced delamination damage

Carbon fiber reinforced polymer (CFRP) is widely used in machinery and construction due to their extra-ordinary mechanical properties. Up to now, conventional drilling is the most common machining process to facilitate holes on CFRP laminates for the component assembly. However, drilling-induced delamination is widely considered as the most undesirable damage and challenging failure mode in this process. The present paper aims to propose a convenient and quick method to predict the mechanical properties of open-hole laminated plain woven CFRP composites more accurately. First, the delamination results of nondestructive test by C-scan and simulation were compared after practical experiment and numerical simulation of drilling process. Second, an equivalent parameter was proposed to simplify the delamination regions with complex boundaries, and the mechanical property evaluation model was constructed by introducing the initial delamination damage area, which was obtained from the drilling numerical simulation results. Finally, the effectiveness of the proposed method was demonstrated by analyzing the mechanical properties and failure modes of CFRP with processing delamination damage under loading conditions of tension, compression and bending. Therefore, the proposed method in this paper can help understand the degradation mechanism of composites after drilling and provide guidance for the design of open-hole laminated plain woven CFRP composites.

Nonlinear Piezoresistive Behavior of Plain-Woven Carbon Fiber Reinforced Polymer Composite Subjected to Tensile Loading

This work aims to investigate piezoresistive behavior in plain-woven carbon fiber reinforced polymer (CFRP). Measurement method for electric resistant alteration in the woven CFRP under tensile loading by using a Wheatstone bridge circuit is introduced. Reversibility of the resistant alteration is also investigated whereas the gauge factor of the woven CFRP is evaluated. The result shows that the positive piezoresistive properties of the woven CFRP can be observed by the Wheatstone bridge circuit. The specific resistances of 43.8 μΩm and 10.1 μΩm are obtained for wrap and thickness directions, respectively. Reversibility with a hysteresis of the woven CFRP can also be confirmed with the gauge factor of 22.9 at loading conditions and 17.7 at unloading conditions. Positive piezoresistive behavior which has been revealed in this work can be utilized for structural health monitoring technology development.