Fiber Epoxy Composites Research Articles

Accelerated aging effects in composites used as repair for pipes in oil industry

AbstractComposites are often employed as repair materials for steel pipelines in the oil industry. Nevertheless, it is known that polymer matrix composites age through service life due to exposure to environmental factors, leading to a decrease in the durability of these repairs. In this work, alterations in glass fiber–epoxy composites aged for 1440, 2880, and 4320 h were studied in two different aging conditions: an accelerated aging chamber (with alternate cycles of exposure to ultraviolet [UV] radiation and water condensation) and immersed in salt water. The effects of aging in the material were evaluated by Fourier‐transform infrared (FTIR) spectroscopy, dynamic mechanical analysis (DMA), lap‐shear tests, permeability analysis, and scanning electron microscopy (SEM) and in terms of mass variation. The results show that chemical changes, as well as alterations in mass and fiber exposure, increases in glass transition temperature and permeability, and more pronounced debonding composite/metal after lap‐shear tests, as compared to unaged materials, occurred. In general, the cycles of UV and water condensation were found to be more harmful to the material than aging in salt water, for the same exposure period.

Radially Grown Graphene Nanoflakes for Tough and Strong Carbon Fiber Epoxy Composites

Radially Grown Graphene Nanoflakes for Tough and Strong Carbon Fiber Epoxy Composites

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.

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.

Improvement on mechanical and flame retardancy behaviour of bio-exfoliated graphene-filled epoxy/glass fibre composites using compression moulding approach

Bio-reduction of composite materials is the modern approach to facilitate the researchers to avoid toxic chemical exposure during reduction process. In this study, the green reduction of graphene oxide using Abutilon indicum (Tamil name: Thuthi) plant leaves extracted from various solvents were used as green filler material (0.3, 0.6 and 1 wt.%) in glass fibre epoxy composite. Compression moulding process was adopted to fabricate bio-reduced graphene oxide (BGO) filler incorporated polymer matrix composite. Tensile, flexural, toughness, impact test and fracture surface morphology analysis have been conducted over developed composite. Flame retardancy behaviour was studied based on UL94 standard. Outcome of the study revealed that Abutilon indicum act as the better reducing agent to reduce graphene oxide. XRD, FTIR results depicts the proper distortion of graphite flask. Addition of BGO in polymer matrix improvises the tensile, flexural and impact strength of matrix material up to 28%, 55% and 80%. Herein addition of 0.6 wt.% of BGO showcase better fracture toughness and flexural strength, further increment in BGO show negative effect in strength. Occurrence of delamination failure was notified in fracture surface morphology.

Evolution of fibre deflection leading to kink-band formation in unidirectional glass fibre/epoxy composite under axial compression

We present the first experimental observation and quantification of the evolution of the three-dimensional (3D) deflection of fibres leading up to kink-band formation in notched unidirectional glass fibre-epoxy composites. This has been achieved by in situ synchrotron X-ray computed tomography (CT) quantified by advanced image analysis. The 3D trajectories of individual fibres were extracted to monitor the change in fibre profiles with increasing compressive load. Initially the fibre trajectory varies significantly from fibre to fibre, the waviness of which cannot be represented by a simple idealised profile. However, the change in the fibre shapes during axial compression is similar for all fibres, as the fibres deflect towards the final kinking direction. The precursor to kink-band nucleation has been identified as a local tilting of fibres in the region where the kink bands ultimately form, defining a micro-buckle band. Even at 99.9% of the failure load this micro-buckle band is much narrower (~150 μm (~12 fibre diameters) wide), and the angle of inclination of the band much shallower (~8°), compared to the final 300–400 μm (25–33 fibre diameters) wide, and 25–30° inclined, kink band. It is notable that kink-band boundaries are delineated by fibre fractures, many of which exhibit wedge-shaped multiple fractures.

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.

The Effect of Alkali Treatment on Physical, Mechanical and Thermal Properties of Kenaf Fiber and Polymer Epoxy Composites.

The use of kenaf fiber as a reinforcement material for polymer composites is gaining popularity, especially in the production of automotive components. The main objective of this current work is to relate the effect of alkali treatment on the single fiber itself and the composite material simultaneously. The effect of temperature condition during mechanical testing is also investigated. Composite materials with discontinuous natural kenaf fibers and epoxy resin were fabricated using a compression moulding process. The epoxy composites were reinforced with 50 wt% untreated and treated kenaf fibers. The kenaf fiber was treated with NaOH solution (6% by weight) for 24 h at room temperature. Kenaf fiber treated with NaOH treatment had a clean surface and no impurities. For the first time we can see that alkali treatment had a damaging effect on the mechanical properties of kenaf fibers itself and the treated kenaf/epoxy composites. The composite reinforced with untreated kenaf fiber and treated kenaf fiber showed increased tensile strength (72.85% and 12.97%, respectively) compared to the neat epoxy. Reinforcement of the composite with treated kenaf fiber decreased the tensile strength due to the fiber pull out and the formation of voids which weakens the adhesion between the fibers and matrix. The temperature conditions also play an important role in composites with a significant impact on the deterioration of composite materials. Treated kenaf fiber has thermal stability and is not sensitive to temperature and as a result reinforcement with treated kenaf gives a lower loss value of 76%.

Experimental study on drilling characteristics of the hybrid sisal–jute fibre epoxy composites

Natural fibre composites have received worldwide attention due to their good mechanical properties, lightweight and low density. Due to these advantages, the natural fibre composites have been used in various engineering applications. Drilling is one of the most frequent machining operations performed on hybrid sisal–jute polymer composites, to assemble the numerous structural components by using mechanical joining process. Furthermore, the machining of fibre reinforced composite material has attracted several researchers because of its non-homogeneous and anisotropic structure. The present research work concerns with the experimental studies on the drilling process of hybrid sisal–jute epoxy composite, using three different types of drill geometry (twist drill, step drill and core drill). The significance of the current work aims to reveal the effect of drill geometry configuration and drilling parameters in terms of drilling-induced force and damages (delamination and surface roughness) for the drilling of hybrid natural fibre composites. Drilling forces, drilling-induced damages and hole quality attributes were experimentally investigated for different drill geometries. The delamination and surface roughness type damages are revealed by microscopic analysis with the help of scanning electron microscope (SEM). The results show that twist drill is best suited for the hole- and force-induced damages.

Tensile characterization of hybridized snail shell filler/glass fibre epoxy composite

Tensile characterization of hybridized snail shell filler/glass fibre epoxy composite

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.

Pin loading effect on 3D spacer fabric-laminated composites produced vacuum infusion

In this study, pin-loading behavior of laminated composites reinforced with three-dimensional (3D) spacer fabric was investigated, experimentally. Failure loads and modes of 3D-woven glass fiber epoxy composites, which are mostly preferred in automotive, machinery, and building production, are determined and compared with the mechanical properties of two-dimensional (2D)-woven fabric-reinforced composite materials. For this purpose, 2D plane and 3D spacer fabric composite plates were produced using the vacuum infusion method. The effect of pin geometry on joint strength and failure mechanism of composite was determined by tensile tests using test apparatus of single and two serial pin joint. In addition, low velocity impact tests of 2D and 3D plates were performed to explain the failure behavior. For mono-layer 3D-woven fabrics, the existence of out-of-plane fiber increases failure strength up to 50% compared to 2D fabrics. On the other hand, the use of multi-layer 3D fabric does not affect changes-specific failure load according to 2D fabrics significantly. Increasing in the specific load is only 9% for two-layers 3D. This situation has also been observed in impact tests.

High content silver/zinc oxide nanoparticle and cobalt nanowire in Caryota urens fibre-epoxy composites for enhanced microwave shielding

Multi reinforcement based composite films has been fabricated and tested for electrical, magnetic and EMI shielding behavior. The main objective of this research was to analyze how a magnetic material is more susceptible to increase the EMI shielding effect than conductive composite. The EMI shield was made using Zinc and Silver nanoparticle, Cobalt nanowire and Caryota urens natural fibres (CUNFs). The hand layup method was used for making shielding composite followed by post curing process at 120 °C for 48 h. The obtained results assured that the hybrid specimens exhibited improved performance by boosting shielding efficiency with increasing concentration of conductive and magnetic fillers. Notably, the SEM micrographs exhibit more adhesion for surface modified surfaces than those unmodified surfaces. A highest attenuation of ~ 50.8 dB was achieved for composite designation SP3, which contains 6phe of ZnO, Ag and Co-nanowire, which confirms the importance of adding magnetic filler. These improved EMI shielding hybrid composites could be used in many applications such as defense products, communication instruments and EMI filters.

Lightweight multi-walled carbon nanotube buckypaper/glass fiber–epoxy composites for strong electromagnetic interference shielding and efficient microwave absorption

Multi-walled carbon nanotube buckypaper (BP) reinforced glass fiber–epoxy (GF/EP) composites were selected to fabricate electromagnetic interference (EMI) shielding and microwave absorbing materials. Six different composite configurations with 3.0 mm thick have been conceived and tested over the X-band (8.2–12.4 GHz). Flexible and low-density (0.29 g/cm3) BP provided a high specific EMI SE of 76 dB with controlled electrical conductivity. GF/EP/BP111 and GF/EP/BP101 composites possess EMI SE as high as of 50–60 dB, which can be attributed to the number of BP inserted and variation in the wave-transmitting layer of the laminates. Furthermore, the shielding mechanism was discussed and suggested that the absorption was the dominant contribution to EMI SE. GF/EP/BP110 laminate demonstrated suitable EMI performance (~ 20 dB), whereas GF/EP/BP011 composite revealed excellent microwave performance, achieving an effective − 10 dB bandwidth of 3.04 GHz and minimum reflection loss (RL) value of − 21.16 dB at 10.37 GHz. On the basis of these results, GF/EP/BP composites prepared in this work have potential applications as both EMI shielding and microwave absorber materials given their facile preparation and lightweight use.

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.

Surface Modification of Areca Fibre by Benzoyl Peroxide and Mechanical Behaviour of Areca-Epoxy Composites

Natural fibre composites are playing great role in current life scenario where the focus is more on replacing synthetic fibre composites with natural fibre composites. In this current study, investigation was done on tensile and flexural behaviour of benzoyl peroxide treated areca sheath fibre epoxy composites. The surface modification of the fibre was confirmed by FTIR analysis. Treatment concentration was the major criteria which effects mechanical properties of the composites. At 4% concentration tensile strength and flexural strength was found to be maximum which was reported as 37.05 N/mm2 and 235.5 N/mm2 respectively which gradually decreased with increasing concentration of benzoyl peroxide. SEM analysis proved that at lesser concentration, the bonding between fibre and resin was effective which reduced as the concentration of benzoyl peroxide increased. This results in ineffective stress transfer between reinforcing material and the matrix which was the reason for failure of composites manufactured at higher treatment concentration.

Ballistic Performance of Guaruman Fiber Composites in Multilayered Armor System and as Single Target.

Multilayered armor systems (MAS) with a front ceramic layer backed by a relatively unknown Amazonian guaruman fiber-reinforced (Ischnosiphon koem) epoxy composites, as second layer, were for the first time ballistic tested against the threat of 7.62 mm rifle ammunition. The amount of 30 vol% guaruman fibers was investigated in three distinct configurations: (i) continuous aligned, (ii) 0–90° cross-laid, and (iii) short-cut randomly dispersed. Additionally, single-target ballistic tests were also carried out in the best MAS-performed composite with cross-laid guaruman fibers against .22 caliber ammunition. The results disclosed that all composites as MAS second layer attended the US NIJ standard with corresponding penetration depth of (i) 32.9, (ii) 27.5, and (iii) 29.6 mm smaller than the lethal limit of 44 mm in a clay witness simulating a personal body. However, the continuous aligned guaruman fiber composite lost structural integrity by delamination after the 7.62 projectile impact. By contrast, the composite with cross-laid guaruman fibers kept its integrity for subsequent shootings as recommended by the standard. The single-target tests indicated a relatively higher limit velocity for .22 caliber projectile perforation, 255 m/s, and absorbed energy of 106 J for the cross-laid guaruman fibers, which are superior to corresponding results for other less known natural fiber epoxy composites.

Monitoring of mechanical properties of prestressed glass fiber epoxy composites over 12 months after fabrication

Fiber prestressing during matrix curing can significantly improve the mechanical properties of fiber-reinforced polymer composites. One primary reason behind this improvement is the generated compressive residual stress within the cured matrix, which impedes cracks initiation and propagation. However, the prestressing force might diminish progressively with time due to the creep of the compressed matrix and the relaxation of the tensioned fiber. As a result, the initial compressive residual stress and the acquired improvement in mechanical properties are prone to decline over time. Therefore, it is necessary to evaluate the mechanical properties of the prestressed composites as time proceeds. This study monitors the change in the tensile and flexural properties of unidirectional prestressed glass fiber reinforced epoxy composites over a period of 12 months after manufacturing. The composites were prepared using three different fiber volume fractions 25%, 30%, and 40%. The results of mechanical testing showed that the prestressed composites acquired an initial increase up to 29% in the tensile properties and up to 32% in the flexural properties compared to the non-prestressed counterparts. Throughout the 12 months of study, the initial increase in both tensile and flexural strength showed a progressive reduction. The loss ratio of the initial increase was observed to be inversely proportional to the fiber volume fraction. For the prestressed composites fabricated with 25%, 30%, and 40% fiber volume fraction, the initial increase in tensile and flexural strength dropped by 29%, 25%, and 17%, respectively and by 34%, 26%, and 21%, respectively at the end of the study. Approximately 50% of the total loss took place over the first month after the manufacture, while after the sixth month, the reduction in mechanical properties became insignificant. Tensile modulus started to show a very slight reduction after the fourth/sixth month, while the flexural modulus reduction was observed from the beginning. Although the prestressed composites displayed time-dependent losses, their long-term mechanical properties still outperformed the non-prestressed counterparts.

Glass/Caryota urens hybridized fibre-reinforced nanoclay/SiC toughened epoxy hybrid composite: mechanical, drop load impact, hydrophobicity and fatigue behaviour

Glass/Caryota urens hybridized fibre-reinforced nanoclay/SiC toughened epoxy hybrid composites were prepared and characterized for its mechanical, drop load impact toughness, hydrophobicity, and fatigue behaviour. The rapidly increasing demand in polymer matrix composites proportionally increasing the environmental pollution and now this factor is a prime concern for all researchers worldwide. Thus, this research study is aimed to prepare and investigate the natural fibre-based polymer matrix composites by keeping the environmental factors in consideration. Replacing the synthetic fibres completely by natural fibre also not a great development since, the natural fibres are inferior in useful properties. Thus, in this present investigation, a hybrid form of glass-Caryota urens fibre was introduce as primary reinforcement for nanoclay-SiC toughened epoxy resin matrix. The mechanical and drop load impact results revealed that the addition of nanoclay and SiC into the epoxy resin improved the toughness together with glass-Caryota urens hybrid fibre. Moreover the addition of nanoclay and Caryota urens fibre in epoxy resin matrix improved the fatigue life cycle up to 55,182 for 50% of ultimate tensile stress. The hydrophobicity of silane-treated reinforcements gives marginal loss in water absorption compared to bare epoxy resin. These properties improved hybrid fibre epoxy composites could be used in many engineering applications.