Carbon Fiber Reinforced Epoxy Composites Research Articles

Effects of cellulose nanofiber content on impact properties of carbon fiber reinforced epoxy composites with the cellulose nanofiber dispersion layer

Cellulose nanofibers (CNFs) are environmentally friendly materials with a high specific strength. To enhance the impact properties of the carbon fiber reinforced plastics (CFRPs), a method for inserting a CNF dispersion layer between prepregs was developed. By using an aqueous solution of epoxy resin, the hydrophobic treatment of CNF became unnecessary. In this study, CFRP with CNF dispersion layers was fabricated with different CNF content. The impact energy absorbed by the CFRP specimen was increased with the increasing CNF content, and the Charpy impact value increased up to a maximum of 21% by the CNF dispersion layers. Highlights Carbon fiber reinforced plastics (CFRPs) specimens with the cellulose nanofiber (CNF) dispersion layer were fabricated. The specimens were fabricated by varying the content of CNF. Impact energy absorbed by the CFRP specimen was increased with increased CNF content. Charpy impact value increased up to 21%; optimum ductility index value was clarified.

Effect of process parameters on mode-II interlaminar fracture toughness and fractographic features of automated fibre placement prepreg laminates

The present study concerns the quantitive assessment of the influence of process parameters on the interlaminar properties of carbon fiber reinforced epoxy composites. Mode II interlaminar fracture toughness is evaluated based on the ENF test. Scanning electron microscopy images are used to evaluate the change in microstructures. The results indicate that the process parameters have a direct influence on the microstructural features and fracture toughness of laminates. Specifically, the elevation of layup speed leads to the increase of interlaminar porosity which results in a decline of fracture toughness. The moderate pressure could sufficiently evacuate air bubbles during the deposition which to a certain extent decreases the porosity; however, the excessive pressure squeezes resin out from the interlaminar region, which decreases the fracture toughness. Furthermore, the excessive temperature could both increase porosity and result in a thinner resin layer due to the change in resin flowability. In which case, the fracture toughness would be significantly decreased.

Processing and mechanical characterization of short carbon fiber-reinforced epoxy composites for material extrusion additive manufacturing

Fiber-reinforced polymer composites have been extensively utilized in recent years as feedstock materials for material extrusion additive manufacturing (AM) processes to improve strength, stiffness, and functionality of printed parts over unfilled printed polymers. However, the widespread adoption of AM of fiber-reinforced polymer composites requires a deeper understanding of the process-structure-property relationships in printed components, and such relationships are not well understood yet. Fiber length is critically important to the mechanical performance of short fiber composites, but very few studies to-date have focused on how the fiber length distribution (FLD) evolves during processing of composite feedstocks and how this evolution affects printing behavior and mechanical properties in 3D-printed composites. In this work, FLD is measured for carbon fiber reinforced epoxy composites over a wide range of ink compositions and shear mixing times, and the distributions are fit with a Weibull-type distribution function. The effects of FLD on the tradeoff between ink processability, ink rheology, printing behavior and mechanical properties are investigated. Furthermore, the effects of printing parameters (nozzle size and print speed) on mechanical anisotropy and fiber orientation distribution (FOD) in printed composites are explored. Mechanical properties of printed composites are characterized via 3 pt-flexural testing, and microstructure is investigated using optical and scanning electron microscopy (SEM), and x-ray computed tomography. Finally, the fitted Weibull parameters are fed into a composite model that incorporates FLD and FOD, and model predictions are found to be in excellent agreement with experimental observations.

Effect of Thermal Ageing on the Mechanical Strength of Carbon Fibre Reinforced Epoxy Composites.

Applications of Carbon Fibre Reinforced Polymers (CFRP) at temperatures over 150–200 °C are becoming common in aerospace and automotive applications. Exposure of CFRP to these temperatures can lead to permanent changes in their mechanical properties. In this work, we investigated the effect of thermal ageing in air on the strength of carbon fabric/epoxy composites. To this end, accelerated artificial ageing at different temperatures was performed on carbon fabric/epoxy specimens. The flexural and interlaminar shear strengths of the aged specimens were assessed by three-point bending and short beam shear tests, respectively, and compared to those of unaged samples. For ageing at temperatures below the glass transition temperature of the resin, , a moderate reduction of strength was found, with a maximum decrease of 25% for 2160 h at 75% . On the other hand, a rapid strength decrease was observed for ageing temperatures above . This was attributed to degradation of the epoxy matrix and of the fibre/epoxy interface. In particular, a 30% strength decrease was found for less than 6 h at 145% . Therefore, it was concluded that even a short exposure to operating temperatures above could substantially impair the load-carrying capability of CFRP components.

Delamination and tool wear in drilling of carbon fabric reinforced epoxy composite laminate

In the present work, drilling experiments were performed on carbon fiber reinforced epoxy composites, fabricated by compression molding. The effect of various process parameters on delamination and tool wear during drilling were investigated. The laminate, after fabrication, was tested to find the elastic modulus, fiber volume fraction and tensile strength. A full factorial experiment with process parameters at three levels each were performed initially to find the optimum cutting condition which was used in the second experiment to compare the performance of four different drill bits with varying geometry. Analysis of delamination and tool wear revealed that the tool with point angle 90°, helix angle 35° was the best tool for drilling carbon fiber reinforced epoxy composites as it resulted in the least delamination and showed no significant tool wear. Tool with point angle 140°, helix angle 30° also performed well while TiAlN coated tool performed poorly due to the erosion of the coating at the cutting edges resulting in increased cutting forces and higher delamination. Delamination and tool wear was observed to be the highest in tool with a point angle of 118°and helix angle 30°.

Damping properties of carbon fiber reinforced composites hybridized with polysulfone (PSF)/cellulose nanocrystal (CNC) interleaves

Damping properties are critical for many applications of carbon fiber reinforced epoxy composites (CF/EP). In this paper, polysulfone (PSF)/cellulose nanocrystal (CNC) nanofibrous membranes were fabricated by electrospinning as hybrid interleaves in CF/EP composites. The damping properties of the interleaved CF/EP composites were measured by the cantilever percussion free-decay method and dynamic mechanical analysis (DMA). The strength and modulus values of the interleaved composites were obtained by tensile and flexural tests. The obtained results showed that after interleaving by the 10%PSF/0.5%CNC membranes, the damping properties of CF/EP composites were enhanced with little loss of mechanical properties. The damping mechanisms were examined and analyzed with the aid of scanning electron microscopy (SEM). It was concluded that the enhanced damping properties were due to the different energy dissipation mechanisms associated with the PSF nanoparticles generated by reaction induced phase separation and the incorporated CNCs in the EP matrix.

Interfacial Properties of ZnO Nanowire-Enhanced Carbon Fiber Composites: A Molecular Dynamics Simulation Study

The interfacial properties of ZnO nanowire (NW)/carbon fiber-reinforced epoxy composites are investigated using molecular dynamics (MD) simulations. An atomistic representative volume element (RVE) is developed in which a single ZnO NW is aligned on carbon fiber and embedded in the cross-linked epoxy. Effects of ZnO NWs on the fiber-matrix adhesion are studied by evaluating the fiber and the enhanced matrix interaction. The traction-separation behavior in both sliding mode (shear separation) and opening mode (normal separation) is evaluated. The cohesive parameters, including the peak traction and adhesion energy, are calculated in each mode. Different numbers of cross-linked epoxy units in the system are studied and validated. The interfacial properties of the hybrid system are compared with the simulated bare RVE containing fiber and epoxy. MD results showed that the interfacial strength is increased from 485 MPa to 1066 MPa with the ZnO NWs. The adhesion energy in both opening and sliding modes is significantly improved by growing ZnO NWs on the carbon fibers. In addition, the hybrid system shows more rate-independent behavior compared with the bare system in the opening mode.

Experimental investigation on the rotating bending fatigue behaviour of glass and carbon fibre-reinforced epoxy composites

ABSTRACT Composite materials have seen a substantial increase in use in aerospace, aircraft and automobile industries as a result of the high expectations on material performance raised by emerging technologies. Fatigue loads are mostly inevitable in these applications. As a consequence, in addition to static strength, current designs require fatigue analysis. Hence, in this investigation, hollow cylindrical composites, constituted by glass and carbon fibres with an epoxy matrix, were considered for evaluating their static and fatigue behaviour. These specimens were tested in load control mode using an in-house built rotating bending fatigue machine at a test frequency of 10 Hz with zero mean stress. To determine the scatter in fatigue life of the developed composite specimens and to create life distribution graphs at any probability of survival percentage, the two-parameter Weibull distribution function was used. Results indicate higher shape parameters for both the composites, at lower stress levels, which represent less dispersions in the fatigue life under high cycle fatigue. Matrix cracking, interfacial delamination, fibre pull-out, and longitudinal splitting of the matrix along fibre failures are observed using a scanning electron microscope.

DETERMINATION OF MECHANICAL PROPERTIES OF COMPOSITE MATERIALS WITH DIFFERENT FILLERS POLYMER MATRIX

In this study, the preparation and characterization of carbon fiber reinforced epoxy composites are aimed at today's increasing use of composite materials. In this study, composite materials consisting of unidirectional carbon fiber-epoxy resin were prepared and the effects of fiber inclination angle on layered epoxy composite materials were investigated using various characterization techniques. Composite materials were prepared by autoclave method. At the stage of characterization of prepared composite materials Scanning electron microscopy (SEM) has been applied for tensile, compression tests and characterization of fracture surfaces to determine the mechanical properties. Keywords: Carbon fiber,epoxy resin,polymer composite,mechanical properties.

Study on Flame Retardancy and Interface Performance of Carbon Fiber Reinforced Epoxy Composites Based on a Modified N-P-Si-containing Sizing Agent

A class of N-P-Si-containing synergistic flame retardant T-K, the phosphoric triamide (TEDAP, T) modified with epoxy silane coupling agent KH560 (K) on molecular polarity and structure, was successfully synthesized and utilized as sizing agent of carbon fiber (CF) for surface treatment in carbon fiber reinforced epoxy (CF/EP) composites. Time of flight mass spectrometer (TOF-MS) and Fourier transform infrared spectroscopy (FT-IR) results showed the successful synthesis of T-K and different degrees of oligomerization of T. Scanning electron microscope (SEM) and interlaminar shear strength (ILSS) characterized the surface and interface morphology of CF and relevant composites, indicating that the interface performance was preserved under selected T-K structure. Thermogravimetric (TG) and limiting oxygen index (LOI) testing results reflected the delayed decomposition of CF on T−5% from 450 °C to 700 °C, and increased LOI values of composites from 34% to 44%, illustrating the significant enhancement on flame retardancy in composites by the application of T-K.

The Effect of Crack Orientation on the Propagation of Cracks in Graphene Nanoplatelet Carbon Fiber-reinforced Epoxy Composites Using Digital Image Correlation

This study experimentally investigated the fracture behaviors of graphene nanoplatelet (GNP) carbon fiber-reinforced polymer (CFRP) composites for varying amounts of GNP reinforcement, crack lengths and crack orientation angles. The specimens were subjected to tensile loading, and their fracture toughness values were determined with respect to maximum damage load and crack length. To compare the results obtained from experimental data, the fracture toughness values, strain distributions and crack tip opening displacements were determined by using a Digital Image Correlation (DIC) technique from images recorded during the tests. The results showed that increasing the amount of GNP increased the fracture toughness of specimens. On the other hand, increasing the crack orientation angle decreased the fracture toughness. Increasing the crack length increased the fracture toughness values for a crack orientation angle of 30° but decreased for a crack orientation angle of 90°. DIC results were found to be compatible with the calculated results using crack length and damage stress values.

On the reliability of residual stress measurements in unidirectional carbon fibre reinforced epoxy composites

The present work introduces a novel methodology to analyse non-uniform residual stresses in composite materials. For robust determination of stresses in complex structures made of different layers, it is first necessary to prove that residual stress analysis in a single layer structure can reliably be accomplished. In present work a unidirectional carbon fibre reinforced epoxy is investigated. For residual stress determination, the integral incremental hole drilling method is used. It is revealed that the standard evaluation formalism for non-uniform stress analysis in isotropic structures is not applicable. A novel methodology based on the formalism for uniform stress analysis in orthotropic materials is introduced and applied for determining non-uniform residual stress states in depth. For calibration, a known load is induced by bending of samples. By comparing data obtained with the known bending stresses, the reliability of measurements is analysed and the novel formalism introduced is validated.

Evaluation of thrust force and delamination in drilling of CFRP by using active spring restoring backup force

Carbon fiber reinforced epoxy composites are typically difficult to machine due to their anisotropic properties which cause delamination and other damages. Introducing a backup plate beneath the workpiece during drilling has proven to be an efficient and cost-effective strategy to circumvent this problem. With a view to reduce the serious fiber pull-out and delamination problems that occur during conventional drilling of CFRP composites, a novel method of active spring restoring backup force is introduced at the bottom side of the workpiece. The thrust force and delamination are determined experimentally during the drilling of holes at various drilling parameters, with and without back-up force. This spring restoring active backup force technique aids in the continuous hole making process and is found to be a simple, inexpensive and versatile technique to adopt for reducing drilling damages. The applied active backup force contributes in the reduction of delamination even at higher thrust force. The optimal backup force is found to be 321.6 N which results in reduced delamination in drilling of composite laminate.

Strain Mapping and Damage Tracking in Carbon Fiber Reinforced Epoxy Composites during Dynamic Bending Until Fracture with Quantum Resistive Sensors in Array

The sustained development of wind energies requires a dramatic rising of turbine blade size especially for their off-shore implantation, which requires as well composite materials with higher performances. In this context, the monitoring of the health of these structures appears essential to decrease maintenance costs, and produce a cheaper kwh. Thus, the input of quantum resistive sensors (QRS) arrays, to monitor the strain gradient in area of interest and anticipate damage in the core of composite structures, without compromising their mechanical properties, sounds promising. QRS are nanostructured strain and damage sensors, transducing strain at the nanoscale into a macroscopic resistive signal for a consumption of only some µW. QRS can be positioned on the surface or in the core of the composite material between plies, and this homogeneously as they are made of the same resin as the composite. The embedded QRS had a gauge factor of 3, which was found more than enough to follow the strain from 0.01% to 1.4% at the final failure. The spatial deployment of four QRS in array made possible for the first time the experimental visualization of a strain field comparable to the numerical simulation. QRS proved also to be able to memorize damage accumulation within the sample and thus could be used to attest the mechanical history of composites.

Fracture Toughness of CNT Filled Carbon Fabric Reinforced Epoxy Composites

ABSTRACT In the present investigation, hand layup processed composites and hot-pressed Carbon matrix reinforced composites were manufactured with and without the addition of carbon nanotubes. The fabricated composites were tested for its mechanical and fracture properties using ASTM testing standards. The results showed that the carbon nanotubes reinforced composites have shown improved tensile and fracture properties when compared with carbon fabric reinforced epoxy composites. The main focus of the present investigation is to study the role and effect of CNT filler as a secondary reinforcement to carbon fibre reinforced epoxy composites. The results of these investigations provide insight into of fracture behaviour of CNT filled carbon fibre reinforced epoxy composites under autoclave chamber.

Thermo-mechanical analysis of seawater-conditioned carbon/polymer composites reinforced with nanoclay/graphene nanoparticles

Increasing demand for the structural materials having high strength, lightweight, corrosion, and environmental resistance is the major reason to consider fiber-reinforced polymer composite (FRPC) materials instead of traditional materials. Synthetic nanoparticle-reinforced FRPC materials have proved to deliver superior performance in many high-end applications. In this study, carbon fiber-reinforced epoxy composites modified with montmorillonite nanoclay (MMT) and graphene nanoplatelets (GNP) were investigated. The prepared samples were subjected to seawater conditioning to exhibit the effect of environmental conditions on the properties of FRPC materials. Frequency sweep dynamic mechanical analysis (DMA) testing was performed in order to characterize the FRPC materials. The results indicated that dynamic mechanical properties of FRPCs were improved by incorporation of nanoparticles. MMT- and GNP-containing samples showed improvement of around 13% in glass transition temperature in the temperature sweep DMA test. Binary MMT/GNP-containing samples showed 10% improvement in glass transition temperature compared to unmodified carbon samples. Frequency sweep DMA test revealed the frequency-dependent properties of FRPCs. With increasing frequency, the storage modulus increased as the material had less time to respond to the applied load. However, at the same frequency, nanophased FRPCs showed higher modulus compared to baseline unmodified samples. Increasing demand for the structural materials having high strength, lightweight, corrosion, and environmental resistance is the major reason to consider fiber-reinforced polymer composite (FRPC) materials instead of traditional materials. Synthetic nanoparticle-reinforced FRPC materials have proved to deliver superior performance in many high-end applications. In this study, carbon fiber-reinforced epoxy composites modified with montmorillonite nanoclay (MMT) and graphene nanoplatelets (GNP) were investigated. The prepared samples were subjected to seawater conditioning to exhibit the effect of environmental conditions on the properties of FRPC materials. Frequency sweep dynamic mechanical analysis (DMA) testing was performed in order to characterize the FRPC materials. The results indicated that dynamic mechanical properties of FRPCs were improved by incorporation of nanoparticles. MMT- and GNP-containing samples showed improvement of around 13% in glass transition temperature in the temperature sweep DMA test. Binary MMT/GNP-containing samples showed 10% improvement in glass transition temperature compared to unmodified carbon samples. Frequency sweep DMA test revealed the frequency-dependent properties of FRPCs. With increasing frequency, the storage modulus increased as the material had less time to respond to the applied load. However, at the same frequency, nanophased FRPCs showed higher modulus compared to baseline unmodified samples.

Effect of fiber content and their hybridization on bending and torsional strength of hybrid epoxy composites reinforced with carbon and sugar palm fibers

This study aims to investigate the effect of fiber hybridization of sugar palm yarn fiber with carbon fiber reinforced epoxy composites. In this work, sugar palm yarn composites were reinforced with epoxy at varying fiber loads of 5, 10, 15, and 20 wt % using the hand lay-up process. The hybrid composites were fabricated from two types of fabric: sugar palm yarn of 250 tex and carbon fiber as the reinforcements, and epoxy resin as the matrix. The ratios of 85 : 15 and 80 : 20 were selected for the ratio between the matrix and reinforcement in the hybrid composite. The ratios of 50 : 50 and 60 : 40 were selected for the ratio between sugar palm yarn and carbon fiber. The mechanical properties of the composites were characterized according to the flexural test (ASTM D790) and torsion test (ASTM D5279). It was found that the increasing flexural and torsion properties of the non-hybrid composite at fiber loading of 15 wt % were 7.40% and 75.61%, respectively, compared to other fiber loading composites. For hybrid composites, the experimental results reveal that the highest flexural and torsion properties were achieved at the ratio of 85/15 reinforcement and 60/40 for the fiber ratio of hybrid sugar palm yarn/carbon fiber-reinforced composites. The results from this study suggest that the hybrid composite has a better performance regarding both flexural and torsion properties. The different ratio between matrix and reinforcement has a significant effect on the performance of sugar palm composites. It can be concluded that this type of composite can be utilized for beam, construction applications, and automotive components that demand high flexural strength and high torsional forces.

Grafting of a novel hyperbranched polymer onto carbon fiber for interfacial enhancement of carbon fiber reinforced epoxy composites

A novel hyperbranched 2,2-bis-(hydroxymethyl) propionic acid polyester-32-hydroxyl (hyperbranched polymer) was selected to graft onto a carbon fiber (CF) surface to enhance the interfacial properties of carbon fiber/epoxy composites. The homogeneous distribution of hyperbranched polymers on the CF surface could increase the wettability, mechanical interlocking and chemical interaction between the CF and epoxy resin. Compared to untreated carbon fiber, the interfacial shear strength (IFSS), interlaminar shear strength (ILSS), and impact strength of the modified carbon fiber/epoxy composite increased by 78.2%, 40.9% and 39.2%, respectively. Furthermore, the thermal stability of the composites improved. The interfacial strengthening mechanism was also investigated by in-depth analysis of the fracture interface microstructure. Interfacial property enhancement was related to the decrease in stress concentration due to the introduction of the gradient modulus interphase induced by the grafted hyperbranched polymer layer.

Performance Improvement of Carbon Fiber Reinforced Epoxy Composite Sports Equipment

This study is to explore the changes in the performance of sports equipment under the action of carbon fiber reinforced epoxy composites. This paper studies the effects of carbon fiber reinforced epoxy composites in pole vault, bicycle, and tennis. The research results show that the performance of sports equipment based on carbon fiber reinforced epoxy composite materials has been greatly improved, with outstanding effects in terms of thermal properties, interface properties, mechanical properties, and fatigue resistance. Carbon fiber reinforced epoxy composite material damage expansion is divided into five stages: matrix cracking, interfacial degumming, delamination, fiber fracture, fracture. Therefore, carbon fiber reinforced epoxy composite materials are comprehensive for the improvement of sports equipment, which has greatly promoted the further development of sports. Carbon fiber reinforced epoxy composite materials can be promoted in other fields, thereby obtaining greater progress with help of high technology. The study of carbon fiber reinforced epoxy composites in this paper has a positive effect on subsequent research.

Progressive damage characterization of biaxial carbon fiber Reinforced epoxy composites

The objective of the work was to investigate bi-axial characteristics of composite materials with cruciform geometry in both experimental and numerical techniques. The carbon reinforced fibers with epoxy composites prepared by hand lay-up technique with various stacking sequences such as 0°/90°, 45°/45°, 15°/75° and 30°/60°. The fabricated composites were machined in cruciform shape, having different notches namely circular, square and rhomboidal according to ASTM – D6856 standard by abrasive water jet machining to ensure dimensional accuracy of ± 0.1 mm. The prepared cruciform specimens were tested using a biaxial fixture developed indigenously by taking the specifications of universal testing machine. The Young’s modulus, proof stress, ultimate tensile strength and fracture toughness were evaluated for 16 specimens of different fibre orientations and notches using software. The response from the biaxial tensile test showed highest stress developing in [0°/90°] Carbon Fibre Reinforced Plastic (CFRP) composites of 61.37 MPa with highest ultimate tensile strength of 71.93 MPa experimentally. Numerical simulation with ANSYS was showing maximum stresses developing in [0°/90°] Carbon Fibre Reinforced Plastic (CFRP) composites 65.37 MPa.