Mechanical Properties Of Carbon Fibers Research Articles

Boosting Mechanical Properties of Carbon Fibers by Gas-Liquid Dual-Effect Approach

Boosting Mechanical Properties of Carbon Fibers by Gas-Liquid Dual-Effect Approach

CRFP Mechanical Properties—Stated Values Versus Experimental Data

Abstract This study thoroughly examines the mechanical properties of carbon fiber-reinforced polymers (CFRPs), motivated by the critical need for accurate composite property data in investigating fracture control measures for structures subjected to barely visible impact damage. We compared experimental results with manufacturer-stated values, focusing on discrepancies in fiber volume fraction and its impact on elastic modulus. Experimental findings showed an increase in elastic modulus to 190 GPa for 0 deg orientation samples, compared to the manufacturer's stated value of 159.27 GPa. The recalculated fiber volume fraction increased from the expected 57% to an actual value of 60.96%. This increase in fiber content, determined through the Voigt modulus equation and corroborated by SEM image analysis, directly contributed to the observed variations in elastic modulus. Tension tests at 0 deg and 90 deg angles exhibited average percentage errors of 14.83% and 11.57%, respectively, while compression tests at 0 deg displayed a deviation of approximately −13.92% after adjusting for values beyond 0.05% compressive strain. The study underscores the critical impact of fiber volume fraction on CFRP properties and highlights the importance of precise empirical evaluation for accurate CFRP characterization in applications such as aerospace engineering.

Tensile properties of helical carbon fiber tows

The carbon fiber used in the load-bearing structural components often exhibits a relatively low toughness and a limited elongation at the point of failure within its carbon fiber tows. To address this challenge, we introduced a bionic helical structure as an innovative alternative to the conventional straight carbon fiber tows, resulting in a novel material characterized by enhanced strength and toughness. Pioneering a theoretical model, we delved into the effects of the helical angle on the tensile mechanical properties of helical carbon fiber tows for the first time. Subsequently, we conducted experimental trials to validate our theoretical findings and identified an optimal range for the helical angle. The optimized helical angle enhances additional lateral interactions, improving the bonding between the fibers and the resin. The characteristics of the helical structure increase the overall fracture elongation of the fiber tows. Tensile tests revealed a remarkable 10.8 % increase in maximum tensile strength and a significant 46 % enhancement in toughness when the tows were fully impregnated with epoxy resin using this optimal helical angle. Incorporating the helical structures at this optimized angle represents a breakthrough in improving the mechanical properties of carbon fiber tows, offering a unique solution to strike a balance between strength and toughness in carbon fiber composites.

Enhancing spinnability and properties of carbon fibers through modification of isotropic coal tar pitch precursor

Producing general-purpose carbon fibers (GPCFs) with excellent properties using an economical raw material such as coal tar pitch (CTP) holds significant importance. To synthesize carbon fibers, the spinnability of precursor material plays an important role. However, the CTP impedes flowability during the spinning process due to possessing high molecular weight complex aromatic structures. To address this limitation, CTP was blended with varying proportions of petroleum pitch (5, 10 and 20 %) and spinnability and flow behavior were analyzed using Rheology measurements. The distinct constitutional properties of petroleum pitch also contributed to alterations in both the stabilization and carbonization processes. Carbon fibers produced from 10PP showed the highest tensile strength and modulus of ∼784 MPa and ∼47 GPa, respectively. The impact of oxidative and carbonization treatments on the resultant microstructural and mechanical properties of carbon fibers was thoroughly examined using various techniques such as FTIR, XPS, XRD, SEM, Raman and UTM. The results showed that the composition of petroleum pitch influenced the stabilization of fibers which eventually affected the carbonization process and resultant properties of carbon fibers. This study offers an understanding of the connection between the precursor's composition, stabilization conditions, and mechanical properties of the resultant carbon fibers.

Research on the thermal conductivity and mechanical properties of carbon fiber reinforced thermoplastic composites doped with different sizes carbon nanotubes: A combination of experiments, numerical simulations and multi‐objective optimization

AbstractWhile improving the thermal conductivity of composites, single‐size carbon nanotubes (CNT) often degrade their mechanical properties due to the agglomerates. To overcome this limitation, this study reported thermoplastic resin matrix composites synergistically reinforced with small, medium, and large‐size carbon nanotubes (S‐CNT, M‐CNT, and L‐CNT). Using the thermal conductivity (λ) and mechanical properties (flexural strength [F], compressive strength [C] and tensile strength [T]) as the response values, we conducted 21 sets of mixing design experiments and developed the associated quadratic term models. Further multi‐objective optimization was carried out for the above response values. Optimized multiscale CNT synergistically modified composites (S‐CNT, M‐CNT, and L‐CNT contents of 1.25, 7.02, and 2.56 wt%) exhibited a λ value of 1.168 W/mK, which was 121% higher than that of pure composite and also superior to the same content of S‐CNT‐ (1.031 W/mK), M‐CNT‐ (1.016 W/mK), and L‐CNT‐modified composites (0.983 W/mK). Additionally, the optimized composite demonstrated excellent mechanical properties (F = 1482 MPa, C = 848 MPa, and T = 1759 MPa), which were 13%, 11%, and 13% higher than those of the pure composites, respectively, and also surpassed those of the S‐CNT‐, M‐CNT‐and L‐CNT‐modified composites.Highlights Using three different scales of carbon nanotubes modified CF/PPBESK composites. Polynomial modeling of composite's thermal conductivity and mechanical properties. Synergistic interactions between carbon nanotubes to improve the composite's thermal conductivity and mechanical properties.

Adjusting the pH of sizing agents to achieve superior interfacial and mechanical properties of carbon fiber reinforced epoxy composites

Interfacial properties were crucial in determining the mechanical properties of carbon fiber reinforced polymer composites (CFRPs). Applying appropriate sizing agents could effectively improve the interfacial properties of CFRPs. However, the influence of the pH of the sizing agents on the interfacial properties of CFRPs was still unclear. In this work, the above issues were elucidated by adjusting the pH of the diethanolamine-modified E51 (E51@DEA) sizing agent to investigate its impact on the interfacial properties of CFRPs. The molecular weight and emulsion particle diameter of E51@DEA increased with increasing pH of the sizing agent, despite the presence of identical chemical functional groups. E51@DEA-pH 7 showed the best interfacial enhancement. It exhibited ILSS and IFSS values of 102.24 and 113.45 MPa, respectively. This showed an increase of 76 % and 37 % when compared with T700. Additionally, the compressive and tensile strength of T700/E51@DEA-pH 7 also improved by approximately 13 % and 30 %, respectively. The suitable molecular chain length of the sizing agent and the high roughness of the surface of CFs were regarded as the contributing factors. This work further provided an effective and simple strategy for adjusting sizing agents to better improve the interfacial properties of CFRPs.

Insight into the structural variation mechanism of highly spinnable isotropic pitch prepared by halogenated model aromatic compounds

This study developed a novel method for synthesis highly spinnable pitch through thermal polymerization of halogenated polycyclic aromatic hydrocarbons (PAH-X) and anthracene oil (AO). The characteristics, average molecular model, and polymerization mechanism of the as-prepared pitches were systematically elucidated. Results show that the thermal cleavage of C-X bonds of the PAHs-X could generate large number of free radicals that greatly facilitate the cross-linking reaction of the active fragments. Namely, the formation of benzyl radicals with high reactivity of the raw materials made it possible to synthesize pitches at lower temperature. The softening point of the as-prepared pitches showed a decreasing trend with increasing of AO proportion due to the abundant carbon content and lower reactivity of AO. Higher temperature could elevate the polymerization activity of aromatic fragments, thus significantly promoted the formation of macromolecular aromatic structures to obtain the spinnable pitch with suitable softening point. The average models validated by calculating the NMR spectra was successfully constructed to demonstrate the condensation degree, which was found be conducive to probe the spinnability of the pitches. Further, the average molecular models could well describe the correlation of the molecular structure, spinnability of pitches, as well as the mechanical properties of carbon fiber.

Polymer/Carbon Fiber Co-modification: Dynamic Compressive Mechanical Properties of Carbon Fiber Modified Polymer Reinforced Concrete

Polymer/Carbon Fiber Co-modification: Dynamic Compressive Mechanical Properties of Carbon Fiber Modified Polymer Reinforced Concrete

Study on the regulation mechanism of interfacial mechanical properties of carbon fiber reinforced aluminum foam sandwich interface

Carbon fiber (CF) is often used to enhance the interfacial properties of porous metal sandwich panel, however, the regulation mechanism on the mechanical properties of the reinforced interface is not clear, which affects its guidance in application. In this study, the regulation mechanism of CF on the mechanical properties of aluminum foam sandwich (AFS) interface was studied from the perspectives of morphology and chemistry. Results showed the effects of CF modification time, modification temperature and content on the interface properties were synergistic. The interfacial strength increased and decreased afterwards as the modification time or temperature or content increased. Fibers aggregation caused by excessive fiber addition could decrease the interface strength. Self-locking and fiber bridging were the dominant reinforced modes and their effects increased as appropriate addition content increased. Guided by the results, the shear strength of AFS interface increased by 79.18 %, the energy absorption increased by more than four times.

Effect of polyphenylene sulfide sulfone sizing agent on interfacial, thermal, and mechanical properties of carbon fiber

AbstractPolyphenylene sulfide sulfone (PPSS) was synthesized by one‐step method and utilized as a sizing agent for carbon fibers. The effects of various monomer ratios, reaction time, and reaction temperature were investigated on the molecular weight of PPSS. The thermal analysis revealed that the product PPSS exhibited a glass transition temperature exceeding 215.5°C, indicating exceptional thermal stability. After PPSS sizing treatment, the grooves on the surface of carbon fibers were filled, resulting in a substantial enhancement of the microinterface properties. The surface energy was increased by 8.2%, while the maximum weight loss temperature was 27.8% higher than that of the commercial carbon fiber. The tensile strength of the carbon fiber after heat treatment reached 2196 MPa, representing a 45.9% increase over that of the commercial carbon fiber.

The Effect of Carbon-Based Nanofillers on Cryogenic Temperature Mechanical Properties of CFRPs.

In the present work, the effects of carbon-based nanofillers (0.5 wt%), i.e., graphene nanoplatelets (GNPs), carbon nanofibers (CNFs), and carbon nanotubes (CNTs), on the cryogenic temperature (77 K) mechanical properties of carbon fiber reinforced polymers (CFRPs) were investigated. The study utilized an ex situ conditioning method for cryogenic tests. The nanofillers were mixed with the epoxy matrix by a solvent-free fluidized bed mixing technique (FBM), while unidirectional carbon fibers were impregnated with the resulting nanocomposites to manufacture CFRP samples. Optical microscopy was employed to analyze the dispersion of the carbon-based fillers within the matrix, revealing a homogeneous distribution in nanocomposites containing GNPs and CNFs. Fracture toughness tests confirmed the homogeneity of the GNP-loaded systems, showing an improvement in the stress intensity factor (KC) by 13.2% and 14.7% compared to the unmodified matrix at RT (25 °C) and 77 K, respectively; moreover, flexural tests demonstrated a general increase in flexural strength with the presence of carbon-based nanofillers at both temperature levels (RT and 77 K). Additionally, interlaminar shear strength (ILSS) tests were performed and analyzed using the same ex situ conditioning method.

Effect of plant short fibers on the mechanical properties of carbon fiber reinforced epoxy matrix by using FEM based numerical homogenization technique

In this study, we utilized the material design library in Ansys Product 2022 R1 to analyze the impact of short plant fibers on the mechanical properties of epoxy resin. We employed the representative volume element (RVE) approach and examined different volume fractions up to 50%. The technique employed in this study was multi-scale modeling based on the finite element method (FEM) for numerical homogenization. Subsequently, we used the same software to develop a five-layer laminated composite. The samples were based on epoxy resin enriched with short plant fibers at fractions of 20% and 30%, as well as pure epoxy resin. The laminated composites were reinforced with carbon fibers. The objective of this study was to analyze the mechanical response of each sample during a tensile test, focusing on multiple parameters. The sought-after results included total deformation, directional deformation, equivalent and elastic stress (Von-mises). The samples containing epoxy resin enriched with 30% of short hemp fibers exhibited remarkable mechanical strength compared to the other samples. These results suggest that the incorporation of short hemp fibers into the matrix led to a significant improvement in the mechanical strength of the composite.

Multiscale simulation and prediction of mechanical properties for carbon fiber reinforced polymer orthotropic laminate

AbstractA multiscale analysis method based on numerical homogenization is presented for predicting the mechanical properties of carbon fiber reinforced polymer (CFRP) orthogonally symmetric laminate. Initially, based on the structural characteristics of CFRP orthotropic symmetric laminate, the relational equations for calculating the mechanical engineering constants from the stiffness coefficient are proposed. Subsequently, the finite element model (FEM) of orthotropic laminate is established. Corresponding subroutines are developed through ABAQUS‐Python to extract and compute the simulation results and obtain the mechanical properties of the laminate. Next, the macroscale mechanical properties are estimated by combining the micro‐scale mechanical model, classical laminate theory (CLT), and volume averaging method. Ultimately, the accuracy of the proposed equations and the feasibility of the numerical homogenization method are demonstrated by comparing the results of numerical simulation predictions, theoretical predictions, and experiments.Highlights Present the relational equations for calculating the mechanical engineering constants of CFRP orthotropic symmetric laminate from the stiffness coefficient. Establish the FEM of orthotropic laminate and develop corresponding subroutines to obtain the mechanical properties of the laminate. Analyze the mechanical properties of orthotropic laminate through microscopic modeling and CLT.

Effect of carbon nanotubes on thermoset curing and mechanical properties of carbon fiber reinforced epoxy resin laminates fabricated by self‐resistance electric heating

AbstractSelf‐resistance electric (SRE) heating for the curing of carbon fiber reinforced plastic (CFRP) offers the benefits of saving energy consumption and reducing investment in equipment. In this work, the investigation was carried out to illustrate the effect of carbon nanotubes (CNTs) addition (0.5, 1.0, and 1.5 wt%) on the thermoset curing and mechanical properties of carbon fiber‐reinforced epoxy laminates fabricated by SRE heating method. The results show that adding CNTs can improve the temperature uniformity and interlayer‐resin flow during the SRE heating process and have a limited influence on the curing degree of CFRP composites. The tensile strength in the longitudinal direction of the composites increased with the increase of CNT addition. Meanwhile, the flexural strength and interlaminar shear strength had the maximum value with the CNTs content of 0.5 wt% and decreased significantly at the CNTs content of 1.5 wt%. It concludes that the appropriate content of CNTs addition has the potential to improve the thermoset curing performance and mechanical properties of the CFRP laminate composites fabricated by SRE heating.Highlights This study focuses on the effect of CNT addition on SRE heating for CFRP. The addition of CNTs improved the temperature uniformity during SRE heating. The addition of CNTs can reduce the voids of SRE‐cured CFRP composites. Threshold value of CNTs affected the mechanical performance of SRE‐cured CFRP.

Nanomaterial-Enhanced Sizings: Design and Optimisation of a Pilot-Scale Fibre Sizing Line

This study focuses on the development of a pilot-scale sizing line, including its initial design and installation, operational phases, and optimization of key process parameters. The primary objective is the identification of critical parameters for achieving a uniform sizing onto the fibres and the determination of optimal conditions for maximum production efficiency. This investigation focused on adjusting the furnace desizing temperature for the removal of commercial sizing, adjusting the drying temperature, as well as optimizing the corresponding residence time of carbon fibres passing through the furnaces. The highest production rate, reaching 1 m sized carbon fibres per minute, was achieved by employing a desizing temperature of 550 °C, a drying temperature of 250 °C, and a residence time of 1 min. Furthermore, a range of sizing solutions was investigated and formulated, exploring carbon-based nanomaterial types with different surface functionalizations and concentrations, to evaluate their impact on the surface morphology and mechanical properties of carbon fibres. In-depth analyses, including scanning electron microscopy and contact angle goniometry, revealed the achievement of a uniform coating on the carbon fibre surface, leading to an enhanced affinity between fibres and the polymeric epoxy matrix. The incorporation of nanomaterials, specifically N2-plasma-functionalized carbon nanotubes and few-layer graphene, demonstrated notable improvements in the interfacial shear properties (90% increase), verified by mechanical and push-out tests.

One‐step in‐situ growth of CNTs on oxidized carbon fiber: Effects of catalyst concentration and growth time on mechanical properties of carbon fiber

AbstractChemical vapor deposition (CVD) method was performed to grow carbon nanotubes (CNTs) on oxidized carbon fiber (CF). First, CF was oxidized by a simple and gentle way to increase the number of active groups and the optimal treatment time was determined. Then, effects of catalyst concentration and growth time on morphologies and loading amount of CNTs, the properties of CF/CNTs reinforcements, and the interlayer properties of CF/CNTs composites were explored. When the catalyst concentration and growth time were controlled at a reasonable level, CNTs can be uniformly grown on the CF surface. The interlaminar shear strength (ILSS) was characterized and the fracture surfaces of CF/CNTs composites were observed. The results demonstrated that when the catalyst precursor was kept at 0.05 mol/L and the growth time was controlled at 10 min, CNTs had the best strength effect and the ILSS increased by 30.25% compared to that of composites without CNTs. The fracture surface showed that CNTs can penetrate the matrix at the interface and enhance the interface through mechanical interlocking effect. The CNTs‐induced interphase allows the stress inside the composites to propagate continuously between resin and fibers, thereby heightening the load carrying capacity.Highlights A simple and gentle way was performed to activate CF without strength reduction. The influence mechanism of various parameters was revealed in detail. The mechanism of CNTs enhancing the interface was revealed.

Effect of voltage on mechanical properties of carbon fiber reinforced concrete

Under various voltages, the performance variations and compressive and flexural failure modes of carbon fiber concrete were investigated. The findings indicate that while the general concrete will display a cone upon failure, the compressive carbon fiber concrete specimen maintains its integrity under the influence of voltage, displaying a state of surface cracking with similar-sized crack spacing. With an increase in voltage level, the compressive strength of carbon fiber reinforced concrete first rises and then falls. The compressive strength of carbon fiber concrete at a voltage level of 15V is 66% higher than that of carbon fiber concrete without voltage. Similar to the flexural strength test phenomenon of uncharged carbon fiber concrete, the flexural strength test phenomenon of concrete beams when applying voltage is immediate fracture. The maximum strength of carbon fiber reinforced concrete is only 10% higher, and the flexural strength is only marginally improved, fluctuating.

Synergism of non‐covalent interaction and ZIF‐8@GO to improve tribological and mechanical properties of carbon fiber reinforced recyclable indole‐based poly(hexahydrotriazine) composites

AbstractExisting research on interfacial interactions of recyclable carbon fiber reinforced poly(hexahydrotriazine) (PHT) composites has mainly focused on the study of reinforcing fibers, ignoring the wide range of applications of matrix in advanced friction materials. Herein, polyhedral ZIF‐8 was grown in‐situ on the GO surface (named as ZIF‐8@GO) to improve the load‐bearing capacity of GO nanosheets. The ZIF‐8@GO with zinc ions and imidazole ions were embedded as interlaminar reinforcement into matrix to construct a non‐covalent cation‐π interaction with indole‐based PHT (In‐PHT) matrix, which significantly enhanced the toughness and tensile strength (reached 215.5 MPa) of composites. With the incorporation of armor‐shaped ZIF‐8@GO reinforcement, compared with the composite without ZIF‐8@GO, the wear track width was significantly decreased by 50%. Moreover, the worn surface lubricated by this composite exhibited efficient self‐healing property due to the introduction of the polyethylene wax (PEW), and the healed average friction coefficient showed slight changes. Extensive analyses verify that the ZIF‐8@GO structure and cation‐π interactions across multiscale interfaces can enhance both mechanical strength and wear resistance of recyclable carbon fiber reinforced In‐PHT composites (In‐PHT‐CFRPs).Highlights ZIF‐8@GO was embedded as interlayer reinforcement to improve wear resistance. Cation‐π interaction across interface enhances interface carrying capacity. Due to strong cation‐π bonding, IPEZGC exhibits outstanding tensile strength. PEW was embedded as healing agent to obtain self‐healing property.

Improved mechanical properties of carbon fiber/epoxy composites via fiber surface grafting of rigid-flexible chain structure

The surface topography and interface characteristics play a significant role in determining the mechanical properties of carbon fiber reinforced polymer (CFRP) composites. These features are primarily influenced by the surface chemical structures and their interactions with the matrix resin. Here, we developed a rigid-flexible coating consisting of polyetheramine (PEA) and polydopamine (PDA) on the fiber surface to control the interface and improve the mechanical properties of CFRPs. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrum (FT-IR) results validated the successful introduction of polymeric chains and fiber surface characteristics including rough surfaces, slim polymer layers and uniform dots were examined by scanning electron microscope (SEM) and transmission electron microscopy (TEM). Contact angle tests indicate that the functionalized coating noticeably enhances the interaction force between carbon fibers, promoting improved wettability by the matrix resin. The bending and interlaminar shear strength of CFRP prepared by functional carbon fiber are increased by 45.76 % and 47.63 %, respectively. The drop weight impact (DWI) test confirms the positive effect of improved interfacial properties on the out-of-plane impact resistance of CFRPs.

Interfacial microstructure evolution and mechanical properties of carbon fiber reinforced Al-matrix composites fabricated by a pressureless infiltration process

In this study, unidirectional carbon fiber reinforced aluminum-matrix (CF/Al) composites were successfully fabricated by using a pressureless infiltration process to infiltrate Ni-coated CFs with Al. The evolution of the interfacial microstructure was investigated. The results showed that the Al–Ni reaction provided the main driving force for infiltration of Al melt into CF bundles by the significantly improving wettability. As the infiltration time increased from 0 min to 8 min, the infiltration behavior gradually improved with fewer defects and better fiber dispersion. Furthermore, the Al–Ni intermetallic compounds (IMCs) transformed from the large-sized primary Al3Ni phase to fine Al3Ni phase with eutectic structure, and were uniformly distributed around the CFs, which was beneficial for transferring the load and preventing the crack propagation. However, the harmful Al4C3 phase grew up at the interface. The ultimate tensile strength (UTS) of the CF/Al composites with the optimal infiltration time of 6 min was 135 ± 4 MPa, which was 121.3 % higher than that of the Al matrix.