Carbon Fiber Epoxy Composites Research Articles

Improving the delamination resistance and impact damage tolerance of carbon fibre-epoxy composites using multi-scale fibre toughening

This paper presents an experimental investigation of the multi-scale toughening mechanisms for improving the interlaminar fracture toughness, low-velocity impact damage resistance and compression-after-impact (CAI) strength of continuous carbon fibre-epoxy composite laminates using carbon nano- and micro-fillers spanning the nanometer to millimeter length scales. The fillers used in the epoxy matrix of the composite laminates were carbon nanofibres (CNFs) and short carbon fibres (SCFs). When used together, these two fillers yielded a less-than-additive improvement to the mode I fracture toughness. However, they created a synergistic (i.e. greater-than-additive) increase to the steady-state mode II toughness, compared to when the fillers were applied separately. Hybridising the CNFs with the SCFs also improved the impact damage resistance (up to 24%) and CAI strength (up to 29%) of the laminate at various impact energies. The key toughening mechanisms imparted by the CNFs and SCFs, when used separately or in combination, were identified through analyses and scanning electron microscopy.

Comparison on the Tribological Properties of Roller and Guide Tribo-Pair Used in Antenna Deployable Structure

The tribological properties of roller and guide tribo-pair are important for the design of deployable structure for space-borne perimeter truss antenna. In this study, carbon fiber epoxy resin composites are used as the guide material; while polyimide and GCr15 steel are used as the roller material. Then, friction coefficient of polyimide ball and GCr15 steel ball against carbon fiber epoxy resin composites disk were compared and investigated on the high-temperature, ball-on-disk tribometer under different operating conditions, respectively. The wear morphology of disk was measured by laser scanning confocal microscope. The results show that the friction coefficient of the polyimide ball against carbon fiber epoxy resin composites tribo-pair has better tribological properties. Meanwhile, the friction coefficients of this pair are mainly depend on abrasive wear under low pressure and velocity conditions while the adhesive wear has dominated influence on the friction coefficient for high pressure and velocity conditions. Besides, the tribological properties of carbon fiber epoxy resin composites are mainly affected by ploughing of surface roughness at low temperature, while by surface debonding at high temperature.

Fractographic study into the effect of drilling damage on bearing mechanisms and performance in Carbon-Fibre epoxy composites

With the widespread adoption of polymer composites in primary structures, understanding and prediction of the performance of composite to metal hybrid joints is now critical to engineering design of transport structures. This work investigated the damage processes associated with bearing failure of such composite joints, for both pristine holes and holes damaged during drilling. An aerospace grade composite was drilled under three different conditions, tested to failure under quasi-static double bearing loading, and then characterised using fractographic techniques. In the pristine condition, the initial damage process was 0° longitudinal splitting tangential to the lateral extents of the hole which then dictated the extent of the subsequent bearing damage development. Beneath the bearing face of the hole inclined lines of in-plane microbuckled fibres had developed whilst beyond the constraint of the washer there was considerable delamination and massive out-of-plane fibre microbuckling. As the degree of drilling damage increased, 0° longitudinal split development was inhibited, and the local pre-existing damage at the periphery of the hole had extended into the bearing damage zone, directly initiating out-of-plane fibre microbuckling. Consequently, the bearing damage zone exhibited irregular distributions of fibre microbuckles, both across the thickness and depth beneath the bearing face of the hole. The observations in this work provide a means to validate predictive models and offer potential routes to improve bearing performance and the tolerance of laminates with drilling damage when under bearing loads.

Laser process parameter optimization of dimple created on oriented carbon fiber reinforced epoxy composites

It was mainly aimed at the study to make the optimization of laser parameters to obtain dimples with the desired shape and size. Carbon Fiber EPOXY composite (CF-EPOXY) surfaces were ablated by Nd:YAG laser which has a 1064 nm wavelength. Some important laser process parameters such as focus position, pulse energy, duration and number were optimized to achieve maximum aspect ratio, circular shape and minimum thermal defect. In addition, it has been determined that which laser parameters are more effective to obtain the desired quality surface. These different shapes and geometry of dimples could be used to improve some properties such as wettability, friction, etc. The pulse energy with an effective rate of 55.97 % is the most effective parameter to achieve the larger aspect ratio. The focus position is the most effective parameter with the rates of 66.18 % and 47.94 % to obtain both perfect circularity and minimum thermal defects respectively. Confirmation experiments were performed and the highest aspect ratio was found as 1.14, the best circular dimple and the minimum thermal effects outside the spot area were found with the rates of 1.021. These are the optimum results of 9 experiment sets in this study for each output. The results were supported by confirmation experiments and regression analysis. It can be concluded that the Taguchi method is reliable and saves time and materials.

Alkali-Activated Mortars Modified by Epoxy-Carbon Fiber Composites Wastes

Short chopped fibers coated by epoxy resin of different length (5 to 10 mm length) were added at low volume content (about 4.6% on the composite) to alkali-activated fly ash or metakaolin mortars. These uncured scraps derive from the production of carbon fiber-reinforced polymer composites and they are not presently recycled, despite their outstanding mechanical properties. The workability, microstructure, porosity, and physical and mechanical properties (mainly flexural strength) of the derived materials were investigated. Superior flexural strength and increased toughness were obtained. An acid treatment of the scraps further improved the mechanical properties of the mortars by changing the chemical structure of the surface, thus increasing the interaction with the inorganic phase. These results foster the use of these wastes to improve the performance of low carbon footprint building materials such as alkali-activated composites in the building industry.

Improved Ablative Properties of Nanodiamond-Reinforced Carbon Fiber-Epoxy Matrix Composites.

The influence of nanodiamonds (NDs) on the thermal and ablative performance of carbon-fiber-reinforced–epoxy matrix compositeswas explored. The ablative response of the composites with 0.2 wt% and 0.4 wt% NDs was studied through pre-and post-burning morphologies of the composite surfaces by evaluation of temperature profiles, weight loss, and erosion rate. Composites containing 0.2 wt% NDs displayed a 10.5% rise in erosion resistance, whereas composites containing 0.4 wt% NDs exhibited a 12.6% enhancement in erosion resistance compared to neat carbon fiber–epoxy composites. A similar trend was witnessed in the thermal conductivity of composites. Incorporation of composites with 0.2 wt% and 0.4 wt% NDs brought about an increase of 37 wt% and 52 wt%, respectively. The current study is valuable for the employment of NDs in carbon fiber composite applications where improved erosion resistance is necessary.

A comparative study of mechanical and machining performance of polymer hybrid and carbon fiber epoxy composite materials

Fiber-reinforced plastics are known as advanced composite materials thanks to their high strength and lightweight features. Carbon fiber reinforced polymers (CFRPs) are one of the high-performance and high-cost fiber-reinforced polymer (FRPs) materials. They are used in several high-performance engineering applications such as motorsports, marine, aviation, energy and defense industry. The cost of carbon fiber is higher compared to many other materials, more competitive and cost-effective productions will spur the demand for composite parts exponentially. Thus, hybrid laminate composite containing carbon and glass fiber materials were manufactured as an alternative for CFRP materials. Because using glass fiber prepreg instead of carbon fiber prepreg will lead the material to become cheaper. However, machining of the FRP materials is still an important issue. For this reason, the present study is focused on the mechanical and machining performance of the polymer hybrid and carbon fiber epoxy composites.

Recycling technology of epoxy glass fiber and epoxy carbon fiber composites used in aerospace vehicles

Materials used for aircraft structures are chosen very carefully with a lot of consideration towards high strength and lightweight properties. Traditionally, metal alloys have been the favourite choice for manufacturers. But aircraft materials have undergone a paradigm shift over the years from wooden structures to composite materials. Epoxy-based composites are widely used in aircraft structures and they are difficult to recycle as thermoset resins are cross-linking, become rigid upon heating and cannot be remolded. As more than fifty percent of aircraft structure, by weight, being composed of composite materials these days, there will be a lot of waste generated when such aircraft reach their end-of-life. This calls for a sustainable approach towards waste management and a move towards recycling. This is a comprehensive study of recycling of composites like Glass Fibre Epoxy and Carbon Fibre Epoxy, the most used composite in aircraft structures. Glass Fiber Epoxy composite can be used in construction applications after processing through mechanical recycling. This investigation throws light on what kind of value-added products can be made from recycling of such composites. Carbon Fibre is an ideal reinforcement material used in aircraft composites and hence its proper reclamation and recycling are also of paramount importance. Thus, the recycling methodology to be followed for Carbon Fibre Epoxy composites, which are placed higher on the economic spectrum, is also discussed.

Loading rate effect of the interfacial tensile failure behavior in carbon fiber–epoxy composites toughened with ZnO nanowires

This paper attempts to study the loading rate effect of interface tensile failure behavior of carbon fiber-epoxy composites toughened with ZnO nanowires (ZnO NWs). ZnO NWs were grown onto woven carbon fiber fabrics through a two-step hydrothermal method, the growth time was carefully controlled to vary the nanowire length. Subsequently, a series of quasi-static and dynamic transverse fiber bundle (TFB) tensile tests were carried out under different loading velocities, ranging from 1 × 10−6 m/s on the universal testing machine to 9 m/s on the electromagnetic Hopkinson bar. A 2D representative volume element (RVE) model has been established to identify the load transfer and failure behavior of the ZnO NW modified interface. The results show that under quasi-static loading, the maximum TFB tensile strength improvement owing to ZnO NWs was about 36.9% and 16.5% when compared with the pristine fibers and the fibers with surface sizing. However, due to the loading rate enhancement of the interface bonding strength, the corresponding values were decreased to 13.9% and 5.0% under dynamic loading. Besides, nanowires with medium length are recommended, because too long nanowires shall reduce the matrix impregnation space between fibers, and the microcracks from the fiber/matrix interface can easily deflect into the matrix along the nanowires. This side-effect may neutralize the enhancement mechanism of ZnO NWs when their length increases to a certain extent.

Heterogeneous Thermoset/Thermoplastic Recycled Carbon Fiber Composite Materials for Second-Generation Composites

With an increase in the use of carbon fiber composites in the aerospace and automobile industry a collateral issue of what to do with end-of-life carbon fiber composites has risen. In this study, we successfully developed a second-generation composite using a heterogenous mixture of thermoset and thermoplastic recycled carbon fiber composites (CFCs). The recovered vinyl ester and epoxy CFCs (thermosets) were characterized using thermogravimetric analysis. Adhesive performance was evaluated through double lap shear tests by melt-bonding a thermoplastic polyether ether ketone (PEEK) CFC to either the thermoset epoxy or vinyl ester CFC. The waste carbon fiber composites were also mechanically milled and classified through screening techniques. The resulting milled materials were used to form and produce composite panels through high temperature compression molding. The influence of particle size and platen temperature were evalauted through mechanical testing. Results indicate that melt-bonding with the vinyl ester/CFC exhibited significantly higher lap shear strength values than that between epoxy/CFC and PEEK. Findings also show that adding thermoset CFCs to the thermoplastic system (PEEK) enhanced the flexural properties of composites.

A novel carbon nanotube nanopaper polyurethane coating for fiber reinforced composite substrates

AbstractHigh performance carbon nanotube (CNT) nanopaper (NP) reinforced polyurethane (PU) nanocomposite coating with high potential for aerospace and automotive applications was successfully fabricated and evaluated in this work. Different PU formulations were used to fabricate nanocomposites to study the effect of hard segment content on resin infiltration and nanocomposite mechanical properties. The process window of PU infiltration into the CNT NP was established by rheology measurements and thermal gravimetric analysis (TGA). The micro‐structure morphology of the nanocomposite was characterized by scanning electron microscope (SEM). Uniform CNT distribution in PU matrix was observed in the high‐resolution SEM images, which indicated good resin impregnation quality. Based on mechanical properties and process window, a PU formulation was selected as matrix to fabricate NP/PU nanocomposite coating for carbon fiber/epoxy composites (CFPC) substrate. The flexural strength and impact resistance of the CFPC were significantly improved by 9% and 14.7% after applying the NP/PU nanocomposite coating. Aimed at industrial applications, a continuous nanopaper fabrication process was successfully demonstrated in this work. Through the process window study, a continuous process to fabricate nanocomposite is proposed for future scale‐up.

Temperature Dependence of Normalized Sensitivity of Love Wave Sensor of Unidirectional Carbon Fiber Epoxy Composite on Mn-Doped 0.24PIN-0.46PMN-0.30PT Single Crystal Substrate

Love wave sensors have attracted significant interest due to their high sensitivity and low attenuation. Love mode acoustic dispersion relation, highest normalized mass sensitivity, optimum normalized waveguide layer thickness, and temperature coefficients of frequency (TCF) were theoretically studied for the carbon fiber epoxy composites (CFEC)/Mn:0.24PIN-0.46PMN-0.30PT structure sensor. The highest normalized mass sensitivity exhibits a decreasing trend as the temperature increases from 25 °C to 55 °C. TCF can be improved by increasing the normalized layer thickness (h/λ); however, the temperature dependence of normalized mass sensitivity decreases. For the carbon fibers (CFs) in the CFEC waveguide along the propagation direction of Love wave, the device has a relatively small TCF of −10.92 ppm/°C at h/λ = 0.4001, where the normalized mass sensitivity is approximately 1.5 times that of a typical fused quartz/ST-quartz configuration device. The theoretical results imply that good temperature stability and high measurement precision were obtained from the device in the system CFEC/Mn:0.24PIN-0.46PMN-0.30PT with the CFs in the CFEC along the propagation direction of Love wave (x-axis). The ideal waveguide material requires a small elastic constant c44; however, the ideal piezoelectric substrate requires large elastic constants c44E and c66E.

Injection Molding of Electrically-Conductive Polymer Composite Bipolar Plates

Bipolar plates are commonly fabricated from graphite, however the associated machining costs are a major limitation to fuel cell commercialization. In addition, graphitic bipolar plates comprise up to 80% of the weight of a fuel cell. Here we propose an alternative approach to bipolar plate manufacturing: injection molding of electrically-conductive polymer composites. Injection molding is well-suited for mass production and polymeric materials can significantly reduce the weight of the bipolar plate. Prior efforts to injection mold polymer composites for fuel cell bipolar plates have resulted in electrical conductivities that do not meet the United States DOE technical targets for bipolar plate conductivity (> 100 S/cm) [1-3]. In efforts to achieve higher conductivities, Hwang et al. compression molded carbon fiber epoxy composites [4]. While compression molding can be used for production of high volumes, injection molding is most ideal for the levels of mass production required for full-scale commercialization of fuel cells. For this reason, we will be investigating the suitability of injection molding polymer composites with sufficient electrical conductivities.In this work, carbon fiber and carbon nanotubes were added to nylon at varying weight percentages. The conductivity of carbon fiber-filled composites ranged from 10 – 20 S/cm. High carbon fiber loadings increased conductivity, however beyond 50 wt%, the increased viscosity of the polymer blends can inhibit proper injection molding. Carbon nanotubes were then added to these composites to investigate the synergistic effects of adding conductive fillers with different aspect ratios. These samples reached conductivities up to 65 S/cm, rising closer to the US DOE technical target. In efforts to achieve higher conductivities, nickel-coated carbon fibers were added to nylon. The conductivities of these samples were above the US DOE target, reaching 150 S/cm. Interestingly, the addition of carbon nanotubes to these composites did not increase conductivity. If successful in a fuel cell, these polymer composites may provide a pathway to cheaper, lighter fuel cells with higher specific energies. Dweiri, R.; Sahari, J., Electrical properties of carbon-based polypropylene composites for bipolar plates in polymer electrolyte membrane fuel cell (PEMFC). Journal of Power Sources 2007, 171 (2), 424-432.Wu, M.; Shaw, L. L., On the improved properties of injection-molded, carbon nanotube-filled PET/PVDF blends. Journal of Power Sources 2004, 136 (1), 37-44.Mighri, F.; Huneault, M. A.; Champagne, M. F., Electrically conductive thermoplastic blends for injection and compression molding of bipolar plates in the fuel cell application. Polymer Engineering and Science 2004, 44 (9), 1755-1765.Hwang, I. U.; Yu, H. N.; Kim, S. S.; Lee, D. G.; Suh, J. D.; Lee, S. H.; Ahn, B. K.; Kim, S. H.; Lim, T. W., Bipolar plate made of carbon fiber epoxy composite for polymer electrolyte membrane fuel cells. Journal of Power Sources 2008, 184 (1), 90-94. Figure 1

Covalent sizing surface modification as a route to improved interfacial adhesion in carbon fibre-epoxy composites

The polymerisation and attachment of a covalent sizing to the surface of carbon fibres is demonstrated using an electrochemical surface treatment. This treatment proceeds in an aqueous environment at a constant potential of −1 V in 2 min, and thus is within the window of current industrial surface treatments (2–4 min). This treatment demonstrates the ability to significantly increase the tensile strength (up to 25%), Young’s modulus (up to 15%) and interfacial shear strength (IFSS, up to 199%) in an epoxy resin. Optimisation of this process gave similar improvements in carbon fibre properties and IFSS at lower monomer concentrations (0.2 M and 0.5 M vs 1.0 M). This treatment is demonstrated on both bundles of fibres and woven fabrics and the woven fabrics are able to be reversibly moulded into different shapes by simply wetting the surface with an appropriate solvent and allowing to dry.

Multifunctional Carbon Fiber Composite with Improved Electromagnetic Interference Shielding and Interlaminar Fracture Toughness Characteristics

In this study, multifunctional carbon fiber-epoxy composites with improved electromagnetic interference shielding and interlaminar fracture toughness were manufactured. The interest in manufacturing multifunctional composites has been driven by the need for materials that simultaneously perform structural and non-structural functions. Unidirectional carbon fiber-epoxy composite laminates stitched with Dyneema13, Copper, and Kevlar13 were prepared using resin infusion process. Representative specimens from the unstitched and the stitched composites were tested using rectangular waveguide and Mode I interlaminar fracture tests. The electromagnetic shielding effectiveness experimental results showed that stitched composites exhibited improved shielding effectiveness compared to unstitched composites. For example, composite stitched with copper showed the highest increase of 102.2% in shielding effectiveness whereas composite stitched with Dyneema13 showed the smallest increase of 75.4% in shielding effectiveness compared to the unstitched. Results revealed that the dominant effect of shielding in these composites is absorption. The Mode I experimental results showed that composite stitched with Kevlar13 exhibited the highest crack initiation interlaminar fracture toughness (GIC-initiation), whereas composite stitched with Dyneema13 exhibited the highest maximum crack propagation interlaminar fracture toughness (GIC-maximum). The experimental results comply with the goal of the study to produce multifunctional composite with improvement in the mechanical and electromagnetic properties.

Influence of Seaweed Filler on Dry Sliding Wear of Carbon Fiber Reinforced Epoxy Composites

ABSTRACT During the last few decades, natural fibers are used as reinforcement in polymer composites and they have been continuously used in the field of automotive, aircraft, and biomedical industries. In this work, carbon fiber polymer composites (CFPC) with seaweed fillers were fabricated using the hand-layup method. Sliding wear experiments were conducted under the dry condition on the fabricated samples. The effect of operating parameters like sliding speed (m/s), load (kg), sliding distance (m), and seaweed filler loading on specific wear rate (Ws) was investigated. Experimental results showed exceptional wear resistance of carbon fiber epoxy composite containing seaweed filler. Especially, 10 wt. % of seaweed fillers offered lower wear rate as compared to conventional carbon composite. In this investigation, a minimum wear rate of 2.4 µm was obtained for the sliding velocity of 1.5 m/sec, applied load of 2 N, and sliding distance of 1000 m in 10 wt. % of seaweed-filled composites. It was noted that resistance to wear in seaweed-filled composite was mainly due to fiber fracture mechanism and microcracking. The increasing trend of impact strength has been well perceived from the dipping trend in specific wear rate on seaweed dispersion in the CF10SW epoxy composite.

Flexural fatigue and fracture toughness behavior of nanoclay reinforced carbon fiber epoxy composites

3-point flexural fatigue and Mode I interlaminar fracture tests were done to study the fatigue life and fracture toughness of nanoclay added carbon fiber epoxy composites. Fatigue life data was analyzed using Weibull distribution function, validated with Kolmogorov-Smirnov goodness-of-fit, and predicted by combined Weibull and Sigmoidal models, respectively. The nanophased samples showed more than 300% improvement in mean and predicted fatigue life. At 0.7 stress level, the nanophased samples passed the ‘run-out’ fatigue criteria (106 cycles), whereas, the neat samples failed much earlier. The interlaminar fracture toughness of nanophased samples was also enhanced significantly by 71% over neat samples. Optical and scanning electron microscopic images of the nanophased fractured samples revealed certain features that improved the respective fatigue and fracture properties of the composites.

Studies on mechanical, thermal and tribological properties of carbon fibre-reinforced boron nitride-filled epoxy composites

This research focuses on the static mechanical, thermal and tribological properties of carbon fibre epoxy (CF/Ep) composites filled with boron nitride (BN) micro-filler powder (BN-CF/Ep). The mechanical properties studied were tensile, flexural, interlaminar shear strength and hardness. The thermal properties studied were dynamic mechanical and thermogravimetric analyses which were analysed through dynamic mechanical analyser and thermogravimetric analyser, respectively. The curing ability and dispersion of BN filler in the Ep and composites were investigated through differential scanning calorimetry, Fourier-transform infrared spectra and scanning electron microscopy. The tribological properties focused were three-body abrasion and dry sliding friction and wear conduct. Three-body abrasion tests were studied with silica sand of 212 µm particle size, 30 N load, 2.38 m s−1 sliding velocity and variable abrasive distances of 250 m, 500 m, 750 m and 1000 m. The dry sliding wear tests were performed using pin-on-disc (POD) wear experimental set-up with 60 N load, 3 m s−1 sliding velocity and variable sliding distances of 1000 m, 2000 m and 3000 m. The results followed the trend of BN1% > BN3% > BN5% composites in all mechanical properties. The carbon fabric reinforcement along with the BN-Ep matrix improved enormously all the mechanical properties except impact resistance. Further, it was exhibited that 1 wt% BN into CF/Ep prompts better mechanical properties with predominant damping capacity and thermal stability. Both the dry sand abrasive wear and POD test outcomes revealed that all BN-CF/Ep composites prompt predominant wear resistance. CF along with BN improves enormously the wear resistance with friction coefficient. Further, it was exhibited that 1 wt% BN into CF/Ep in both three-body abrasive and POD tests prompts better wear resistance. Generally speaking, it was presumed that BN-CF/Ep gracefully and successfully improved the mechanical, thermal and tribological properties and morphology of Ep for various mechanical, electrical components and load-bearing applications used in automotive and engineered applications.

Low cost textile-grade carbon-fiber epoxy composites for automotive and wind energy applications

Carbon fiber reinforced polymer composites are highly desirable for automotive and wind energy applications due to advantages associated with weight reduction, high stiffness and strength, durability, and recyclability. The high cost of carbon fiber has been a limiting factor in its widespread adoption in non-aerospace applications. A low cost (estimated < $11 per kg) wide tow (450-600k) carbon fiber derived from textile grade polyacrylonitirile precursor, and hence called Textile Grade Carbon Fiber (TCF) is introduced in this paper. Fundamental aspects of the TCF are discussed along with a detailed characterization of its mechanical properties. Two manufacturing processes relevant to automotive and wind energy applications are considered, namely-compression molding and resin infusion. At various stages the TCF has been compared to commercial non-aerospace 50k carbon fiber composite. Detailed physical and mechanical properties including tensile, flexural, compression, and interlaminar shear properties are reported and compared to non-aerospace carbon fiber composite. The results provide a means for designers and end-users in the automotive and wind energy sector to consider different forms of economical non-aerospace carbon fibers.

Graphene oxide modified carbon fiber reinforced epoxy composites

Abstract The interfacial interaction between the fiber and matrix is the most important factor which influences the performance of the carbon fiber-epoxy composites. In this study, the graphitic surface of the carbon fibers was modified with graphene oxide nanomaterials by using a spray coating technique which is an easy, cheap, and quick method. The carbon fiber-reinforced epoxy matrix composites were prepared by hand layup technique using neat carbon fibers and 0.5, 1 and 2% by weight graphene oxide (GO) modified carbon fibers. As a result of SEM analysis, it was observed that GO particles were homogeneously coated on the surface of the carbon fibers. Furthermore, Young's modulus increased from 35.14 to 43.40 GPa, tensile strength increased from 436 to 672 MPa, and the elongation at break was maintained around 2% even in only 2% GO addition.