Strength Of Epoxy Research Articles

High strength epoxy system modified with soft block copolymer and stiff core-shell rubber nanoparticles: Morphology, mechanical properties, and fracture mechanisms

High strength epoxy system modified with soft block copolymer and stiff core-shell rubber nanoparticles: Morphology, mechanical properties, and fracture mechanisms

Mechanical Behavior of Coir Fiber Reinforced Epoxy Composites with Variable Fiber Lengths

Most studies on the application of natural fibers as reinforcement in polymer composites are growing as a result of the changes in characteristics that fibers can provide for the product. This can be achieved by manufacturing of composites using Hand Layup process. The 2% NaOH fiber treatment was performed to improve fiber-matrix interfaces making spathe- fibre-reinforced composites better mechanical characteristics. Filler loadings as 5% by volume of coir fiber are selected as reinforcement in composites. The varying lengths of fiber chosen as 5mm, 10mm & 15mm and resin-hardner ratio are maintained as 10:0.8. A total 3 numbers of plates with volume as 300 х 300 х 4 mm3 were produced and specimens as per the various ASTM standard were tested to determine the ultimate various Mechanical properties for different configuration. The strength of epoxy resin / coir fiber composites was noticed at a maximum 15 mm (15.27 N / mm2) fiber length. The maximum impact strength of the charpy was also 15 mm fiber length (9.87 kJ / m2).The Experimental results were validated using a numerical method technique in FEA software. The obtained results by experimentation and Finite Element Analysis are very much closer to each other. The results show good mechanical properties and hint us as a replacement for conventional materials in industrial applications.

High strength and toughness epoxy nanocomposites reinforced with graphene oxide-nanocellulose micro/nanoscale structures

The prepared micro/nanoscale structure had a strong and flexible 2D graphene oxide (GO) component (elastic modulus 250 GPa) with a high aspect ratio of 1D nanocellulose (NCC), which possessed excellent mechanical properties (elastic modulus 150 GPa) and was a versatile material for enhancing epoxy (EP) nanocomposites. In this work, we had proposed a strategy for chemically assembling a micro/nanoscale structure comprising GO grafted with NCC (GO-NCC). The GO-NCC, combined with the dense, covalently and hydrogen bonded EP molecule, led to highly effective load transfer between the micro/nanoscale structure and the EP. The inclusion of NCC effectively increased the contact area between the GO and EP and enhanced the interfacial strength and contact surface area of the GO-NCC/EP composite, contributing to its excellent mechanical properties (high toughness and strength). The GO-NCC provided dual advantages over conventional GO in its prominent reinforcement and toughening of the EP composite. Only 0.3 wt% of the GO-NCC was needed to significantly increase the tensile strength and Young's modulus by 69% and 13%, respectively, compared to those of the pristine EP. Moreover, the nanocomposite showed a 244% increase in critical stress intensity factor (KIC) and an 801% increase in critical strain energy release rate (GIC).

Effect of sulfuric acid solution on thermal conductivity and impact strength of epoxy resin reinforced by silicon dioxide powder

In this search, Ep/SiO2 at (3, 6, 9, 12 %) composites is prepared by hand Lay-up method, to measure the change in the thermal conductivity and Impact Strength of epoxy resin before and after immersion in H2SO4 Solution with a 0.3N for 10 days. The results before immersion decreases with the increase of the weight ratios of the reinforcement material (SiO2), It changed from (82.6×10-2 to 38.7×10-2 W/m.°C) with change weight ratios from (3 to 12) % respectively, but after immersion time in the chemical solution where it was (65.6×10-2 W/m.°C) at the weight ratios (6 %) and became (46.6 × 10-2 W/m.°C) after immersion in sulfuric acid. The results of the Impact strength decreased by increasing the percentage weight ratio, it changed from (1.48 to 0.87 kJ/m2) with change weight ratios from (3 to 12) % respectively, but found an increase in the value of Impact Strength after immersion in the chemical solution Where it was (1.28 kJ/m2) at the weight ratio of 6 % and became (1.82 kJ/m2) at the same weight ratio after immersion in sulfuric acid at normality of 0.3 for 10 days.

Preparation of high peel strength and high anti-aging epoxy adhesive that used for bonding aluminum alloy without surface treatment

In the case of bonding of aluminum alloy, surface pretreatment have been widely adopted for adherends so as to achieve superior adhesive performance. However, the strict surface treatment of the aluminum alloy cannot be implemented without special equipment and the mechanical properties, corrosion resistance and aging resistance of the common adhesives cannot meet the demand without surface treatment. Here, acrylic oligomer modified by carboxyl terminated organosilicon and nano alumina were used to modify an epoxy formulation based on a classical DGEBA monomer to produce a high peel strength epoxy adhesive that can be used without surface pretreatment. The peel strength and the shear strength of the adhesive could reach 7.18 N/cm and 18.75 MPa, respectively, and could be well maintained under −70 °C and 100 °C. The novel adhesive also has good heat aging resistance, water resistance and artificial seawater resistance. SEM and XPS were used to investigate mechanism of aging resistance of modified adhesives without surface treatment.

Effects of consecutive processing between cleaning and deposition on adhesion of diamond-like carbon prepared by plasma-based ion implantation and deposition

The effects of pretreatment on adhesion, which is the most important challenge of diamond-like carbon (DLC) films, were investigated. DLC films were prepared by changing pretreatment conditions on austenitic stainless steel (SUS304) substrates by hybrid process of plasma-based ion implantation and deposition (PBIID) using superimposed RF and negative high-voltage pulses. Although an oxide layer on a substrate surface was removed by Ar-plasma sputter cleaning, the substrate surface was immediately reoxidized when plasma was stopped for a moment between sputter cleaning and deposition. The DLC film on the oxide layer was poor adhesion strength less than approximately 50 MPa. Even if the oxide layer existed on the substrate surface, carbon ion implantation as an interface treatment in the PBIID process broke the oxide layer. As a result, the adhesion strength of DLC films was enhanced above the strength of epoxy resin (about 70 MPa). Furthermore, it was found that continuous generation of plasma after sputter cleaning was able to suppress reoxidation of the substrate surface. Consequently, the adhesion strength of DLC films prepared with no interface treatment was increased above 70 MPa, suggesting simplification of coating process and reduction in processing time for cost reduction.

The effect of adding CoFe2O4–CdS nanoparticles on the mechanical properties of rice husk ash epoxy composite: an experimental approach

In this paper, first, cobalt ferrite and cadmium sulfide nanostructures were synthesized through precipitation method. Thereafter, CoFe2O4 nanocomposite as core–shell structure with magnetic cobalt ferrite core and cadmium sulfide shell was synthesized through chemical method. Afterward, the effect of the synthesized nanocomposites along with rice husk ash microparticles (RHAMPs) on the mechanical properties of epoxy resin (EP) has been investigated. Epoxy resin (Epikote 828) and polyamine hardener have been used to prepare the nanocomposite samples. CoFe2O4–CdS nanocomposites with weight percentages of 0, 0.5, 1, and 2% mixed with 3% of rice husk ash microparticles (RHAMPs) were distributed inside the epoxy resin (EP). The prepared products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and alternating force gradient magnetometer (AFGM). The mechanical properties of the epoxy nanocomposites/RHAMPs were also determined using uniaxial tensile standard and three-point bending tests. The results associated with the mechanical tests also showed improvement in tensile modulus, bending modulus, and strength of epoxy resin by adding nanoparticles along with rice husk ash to the epoxy matrix.

Epoxy Resin Systems for Rapid Repair of Steel Members with Carbon Fibre

The repair of steel members with carbon fibre has applications in a broad variety of disciplines. Experimental work in the literature has typically identified high strength epoxy resins to bond the carbon fibre to the steel surface, with requirements of up to two weeks curing at ambient temperature, as recommended by the epoxy manufacturer. However, there may be applications in which repair in the field would require more rapid curing, so as to minimize disruptions to the service of the member or structure. This study presents an experimental program assessing four different epoxy resins for their strength and cure time. Double strap tension tests were undertaken, and the results indicated that certain epoxy resins reached full strength much more rapidly than others, while their strengths varied notably. Recommendations are made with respect to rapid strength repair of steel members with carbon fibre.

Outstanding cavitation erosion resistance of hydrophobic polydimethylsiloxane‐based polyurethane coatings

ABSTRACTCavitation erosion will create shock waves and water jets in turbulent flows. These impact pressures will affect the surface, which will lead to crack propagation and severe material degradation. In this study, we have developed hydrophobic polydimethylsiloxane‐based polyurethanes (Si‐PUx) with hydroxypropyl polydimethylsiloxane (H‐PDMS) and polytetramethylene glycol (PTMG) as mixed soft segments and 2,4‐tolylene diisocyanate, 1,4‐butanediol, triethanolamine as hard segments via a polycondensation reaction and studied its properties. The cavitation wear experiment showed that the cavitation erosion resistance of Si‐PUx coating continuously improved with the increase of H‐PDMS content, while the adhesion force of Si‐PUs reduced with the increasing of H‐PDMS content. The surface of Si‐PUx coating after cavitation test was observed using an optical microscope and three‐dimensional profiler. The cumulative mass loss of Si‐PUx with 12.5 wt % H‐PDMS was only 2.96 mg and the surface showed no obvious holes and cracks after 80 h cavitation. The results showed that cavitation resistance had a correlation with degree of water resistance, hardness, adhesion strength, and dynamic mechanical properties of coating. It seemed that the Si‐PUx coating could withstand a longer period cavitation erosion resistance compared to high strength epoxy, which could be used as protective coating for flow components under water. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2019,136, 47668.

The effect of carbon nanotubes on the curing process and the strength of epoxy resin

The influence of carbon nanotubes of “Taunit-M” of various modifications (carboxylated, carboxyl-hydroxylated, amidated) on the viscosity of the liquid state, gelation, and the strength of the cured epoxy resin “Inject-T” was investigated. For the first time it was found that the introduction of carbon nanotube in epoxy resin at 25 °C increases the viscosity by 4-55 %, at 50 °C it increases by 5-52 %, at 70 °C – by 6 %. The most discernable effect on the viscosity of epoxy resin is obtained for amidated carbon nanotubes. Gel time at 150 °C epoxy resin was 6.3 minutes, with the introduction of carbon nanotube increased to 11.3-13 minutes. Increasing pot life is very important for the technology of using epoxy resin. The first 3 minutes of gelation of the epoxy resin were studied, while the energy loss modulus of the epoxy resin gel without carbon nanotubes monotonically increases over time from 0 to 0.05 MPa, with the introduction of carbon nanotube into the epoxy resin, the loss modulus increases within the first 1-2 minutes from the start of the gel time to the values of 0.14-0.38 MPa (depending on the modification of carbon nanotube), then falls sharply. This means that after the gel time the carbon nanotubes substantially accelerate the process of solidification of the epoxy resin. The strength of the cured epoxy resin was 172 MPa, the introduction of carbon nanotubes increased the strength to 210 MPa. Thus, the introduction of carbon nanotube in epoxy resin slightly increases its viscosity in the liquid state, substantially prolongs the gelation time, accelerates hardening from the moment of gelling, increases the strength of the cured epoxy resin.

Synthetic granite composite for precision equipment structures

The structure is a component that plays an extremely important role in the equipment’s performance, it must withstand efforts without compromising the function, receive and transfer heat, dampen vibrations and position the elements, as well as promote ergonomics and aesthetics. In lightweight and precision equipment’s the raw material used must also allow thin walls, rigid, resistant and low density. The objective of the present work is the development of a synthetic granite composite for manufacturing of equipment’s structures. For this, an abundant Brazilian granite, a high strength epoxy resin and segmented carbon fibers were selected as materials. Test specimens, with maximized packing with granite gravel less than 2.0 mm were fabricated and tested for tensile strength, compression, flexural, damping, hardness, dilatometry, thermal conductivity and density. The maximized composition supported flexural stresses above 42 MPa, without fiber reinforcement and 51 MPa with carbon fiber reinforcement. The damping coefficient was about 7 times higher than cast iron, coefficient of thermal expansion of 1.4E-05 m/m.K, thermal conductivity coefficient of 1.2 W/m.K and density of 2.1 g/cm³. The developed composite showed potential for refining structures, with ease of molding of thin-walled elements, use of inserts, re-machining, providing economical manufacture of single parts, and is still able to perform the function with high damping coefficient and low weight. Keywords: Synthetic granite, composite, machine structure, damping

Effect of nanocomposites on the dynamic properties of repaired flexural elements

Application of modern techniques to rehabilitate structural elements due to aging and/or flexural cracks is of great concern by many researchers. In the current research, high strength epoxy matrix incorporated Carbon Nano Tubes (CNT) was used to bridge up the gaps in the vicinity of flexural cracks. First, the physical properties of CNT were studied followed by mechanical examination of the epoxy resin with/without CNT. The dynamic behavior of simply supported concrete and steel beams, as well as a cantilever steel beam was investigated. All the examined beams were excited by a light impact hummer at their sound, cracked, and repaired states. The free vibration response was collected, processed and the modal parameters were obtained. The change in the dominant natural frequency and damping ratio were investigated in each of the examined condition. The degradation in the beams was created by generating synthetic cracks at the locations of maximum bending moment using a saw cut. Furthermore, intensive numerical finite element modelling (FEM) was carried out using (ANSYS). The obtained numerical results were of great coincidence to the experimental work. It was concluded that the use of epoxy matrix containing CNT enhanced the dynamic properties of the cracked beams and was able to restore the integrity of the beams to a condition slightly the same as their original sound states.

Enhanced Flexural Strength of Tellurium Nanowires/epoxy Composites with the Reinforcement Effect of Nanowires

Investigating the mechanical properties of polymer nanocomposite materials has been greatly increased in the last decade. In particular, flexural strength plays a major role in resisting bending and shear loads of a composite material. Here, one dimensional (1D) tellurium nanowires (TeNWs) reinforced epoxy composites have been prepared and the flexural properties of resulted TeNWs/epoxy nanocomposites are studied. The diameter and length of the TeNWs used to make TeNWs/epoxy nanocomposites are 21±2.5 nm and 697±87 nm, respectively. Plain and TeNWs/epoxy nanocomposites are characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential thermal analysis (DTA). Furthermore, significant enhancement in the flexural strength of TeNWs/epoxy nanocomposite is observed in comparison to plain epoxy composite, i.e. flexural strength is increased by 65% with the addition of very little amount of TeNWs content (0.05 wt.%) to epoxy polymer. Structural details of plain and TeNWs/epoxy at micrometer scale were examined by scanning electron microscopy (SEM). We believe that our results provide a new type of semiconductor nanowires based high strength epoxy polymer nanocomposites.

Evaluation of dynamic interfacial strength of epoxy resin by using laser shock wave

Evaluation of dynamic interfacial strength of epoxy resin by using laser shock wave

Evaluation of Flexural Strength of Epoxy Resin Based hybrid Composites Reinforced with Jute, Banana and Flax Natural Fibers for Bio medical applications

In recent days the concern for the environmental pollution and the prevention of non-renewable and non- biodegradable resources has promoted research in the field of green technologies, eco friendly, non polluting materials which can maximize energy and resource savings. In the present work Jute fibres reinforced with uniaxial glass fibres in epoxy matrix, alongside Banana fibres reinforced with biaxial glass fibres in epoxy matrix and Flax fibres reinforced with biaxial glass fibres in epoxy matrix was prepared and mechanical properties were evaluated and compared for two weight fractions, the samples were prepared by using the hand lay-up process and applying pressure at room temperature. The samples were subjected to flexural testing was performed on the samples to investigate the bending properties and to suggest a material which could compete with synthetic materials and still be easily disposed.From the results, it is easily evident that flax performs better than jute and banana for the flexural strength showing higher values for flexural strength and modulus and hence this fiber can be used for biomedical applications.

About the Mechanism of Stress-Strain State of Epoxy Resin by Carbon Nanotubes

Epoxy resin (ER) and composite materials based on it play an important role in engineering and technologies. The wide use of epoxy resins derived from their strength and unique combination of performance characteristics. The article considers 2 aspects influencing the strength of ER: rates of strain and modification of ER by the carbon nanoparticles (CNT). The experiments were conducted on the ER of brand and Etal Inject-T hardener. The strain of samples was carried out at speeds of 1 mm/min, 2 mm/min, 5 mm/min and 20 mm/min. The experiments showed that the stress-strain curve consists of three successive zones—elastic, plastic and elastic-plastic strain at small strain rates of 1-5 mm/min. With increasing of strain rate the zone of plastic strain is gradually transformed in elastic-plastic, the average modulus of elasticity increases. At the strain rate above the critical value (about 20 mm/min.) the zones of plastic and elastic-plastic strain disappear, only the zone of elastic strain remains, while the sample is destroyed by the formation of cracks and chips. The initial and functionalized CNTs of Taunit-M brand were used in the experiments. It is found that the initial CNT, introduced in ER do not affect the course of the stressstrain curve, and functionalized CNT with a mass content of 0.05% give different effect on the strain zones: the effect is not felt in the zone of elastic strains, give hardening up to 25% in the plastic zones and elastic-plastic strain. With the increase in input of functionalized CNTs up to 0.2%, the hardening effect of ER was reduced almost in 2 times in the zones of plastic and elasticplastic strain.

ADHESION OF BIOCOMPATIBLE TiNb COATING

Preparation of a coating with a high quality requires good adhesion of the film to the substrate. The paper deals with the adhesion of biocompatible TiNb coating with different base materials. Several materials such as titanium CP grade 2, titanium alloys Ti6Al4V and stainless steel AISI 316L were measured. Testing samples were made in the shape of small discs. Those samples were coated with a TiNb layer by using the PVD method (magnetron sputtering). Onto the measured layer of TiNb an assistant cylinder was stuck using a high strength epoxy adhesive E1100S. The sample with the assistant cylinder was fixed into a special fixture and the whole assembly underwent pull-off testing for adhesion. The main result of this experiment was determining the strength needed to peel the layer and morphology and size of the breakaway. As a result, we will be able to determine the best base material and conditions where the coating will be remain intact with the base material.

Development and evaluation of the coaxial cable casing imager: a cost‐effective solution to real‐time downhole monitoring for CO2 sequestration wellbore integrity

AbstractCO2 leakage is a major concern in a geological carbon sequestration projects due to adverse environmental consequences, where the main leakage risk is identified to be along existing wells through a thick, low‐permeable cap rock. To pursue robust and cost effective real‐time downhole monitoring technology for CO2 sequestration wellbore integrity, a permanently deployed coaxial cable casing imager is developed and evaluated in laboratory in this paper. The prototype of the casing imager consists of evenly distributed coaxial cable strain sensors helically wrapped around the pipe. The system is deployed on both PVC pipe and steel pipe to test its performance in casing deformation monitoring, including axial compression, radial expansion, bending, and ovalization. The strain sensors are pre‐stressed and then helically wrapped onto the pipe with high strength epoxy. Multiple linear variable differential transformers (LVDTs) or strain gauges are used as an independent measurement of the actual pipe deformation in comparison to the casing imager measured pipe deformation. The test results demonstrated the ability of the lab‐scale casing imager prototype in real‐time casing deformation monitoring, including axial compression, radial expansion, bending, and ovalization, which would prove of great value in evaluating wellbore integrity state and providing early warnings of leakage risk that will contaminate the groundwater during CO2 injection. The low cost and high robustness of the distributed coaxial cable sensors will greatly lower the downhole monitoring cost and increase the system longevity. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd.

Influence of phenylphosphonate based flame retardant on epoxy/glass fiber reinforced composites (GRE): Flammability, mechanical and thermal stability properties

In this work, flame-retardant glass fiber reinforced epoxy composites (FGRE) were successfully prepared via adding a novel phenylphosphonate-based flame retardant, N, N'-diamyl-p-phenylphosphonicdiamide (P-MA) into GRE. FGRE12 showed high LOI value of 33%. Meanwhile, FGRE12 passed V-0 rating in UL 94 test and the peak of heating release rate (pHRR) decreased by 54% in comparison with that of GRE. The flame-retardant efficiency of P-MA in GRE was compared with that in epoxy matrix (EP). Moreover, the influences of P-MA on mechanical and thermal stability properties of GRE were studied systemically. Dynamic mechanical analysis (DMA) studied the influence of P-MA on viscoelasticity of GRE. Fiber push-in test and three-point-bending test were used to evaluate the influence of P-MA on the EP matrix/fiber interface strength and interlamilnar shear strength, respectively. In addition, nanoindentation test was used to study the hardness and Young's modulus of EP matrix. The above results showed that the addition of P-MA did not affect the hardness of epoxy matrix and interfacial strength (epoxy matrix/glass fiber). The influence of P-MA on thermal stability of GRE was studied by thermalgravimetric analysis (TGA). These results would be very important in designing new generation multifunctional epoxy-based composite materials.

Bond behaviour of Steel Reinforced Polymer strengthening systems

Steel Reinforced Polymer (SRP) systems, consisting of Ultra High Tensile Strength Steel cords and epoxy resin, are emerging as an effective and cost efficient solution for the externally bonded strengthening of structures. Their applications in civil engineering are more recent than those with Fibre Reinforced Polymers (FRP) employing carbon, glass or aramid textiles, and their mechanical properties still need to be deeply investigated. This paper presents an experimental study on SRP reinforcements comprising textiles with 4, 12 and 18cord/in density. First, the mechanical properties of both textiles and SRP composites were derived through direct tensile tests. The shear bond behaviour, which is crucial for the effectiveness of most applications, was then investigated on strong and weak concrete, tuff, clay brick and brick masonry substrates, providing information on bond strength, failure mode, load-slip response and effective transfer length. Finally, test results and data available in the scientific literature are collected to calibrate the tuning coefficients for the estimate of the bond strength according to the design relationships provided by the Guidelines on FRP.