Adhesion Of Epoxy Composites Research Articles

Mechanical and thermal properties of graphene and carbon nanotube reinforced epoxy/boron nitride adhesives

Outstanding mechanical properties and high thermal conductivity epoxy composites are being developed and are becoming urgent in the electronic and aerospace industries. Boron nitride nanosheet (BN), a nanomaterial with high thermal conductivity, and its epoxy composite adhesive have high thermal conductivity. However, due to its characteristics, the mechanical properties of BN/epoxy will decrease when more BN is added. Therefore, this study graphene platelet and carbon nanotube are selected and packed epoxy/BN composite adhesives to develop adhesives with excellent mechanical properties and thermal conductivity at the same time. In this study, an enhancement effect between a graphene platelet (GnP) and a carbon nanotube (CNT) within an epoxy/BN composite is reported. In the three-phase composite adhesive, the 2 D graphene platelets and 1D carbon nanotubes form a global bearing force network, and the boron nitride nanosheets provide high heat conduction inside the epoxy. They both complement each other in developing thermal conductive and high mechanical energy epoxy composite adhesives. At filler ranging from 0 to 1.0 wt%, epoxy/BN-CNT can improve the fracture toughness (K 1c ), critical stress-energy release rate (G 1c ) and Young's modulus of pure epoxy, are 89, 484, and 67% compared to 52, 286, and 42% in epoxy/BN-GnP composites, respectively. When adding 5.0 wt% of BN-CNT, the epoxy composites' thermal conductivity is up to 0.8 W/m%K, 400% higher than pure epoxy. This article also tested the electrical conductivity of epoxy/BN-CNT and epoxy/BN-GnP composites and found that the electrical conductivity was increased by 12 and 10 orders of magnitude, respectively, and it could be used as an antistatic material. Investigating the enhanced mechanism of epoxy/BN/CNT and epoxy/BN/GnP composites by scanning electron microscopy analysis. Lap shear strength tests on epoxy composite adhesives confirm the reinforcement effect of GnP and CNT of epoxy/BN composites.

Using redox active molecules to build multilayered architecture on carbon fibers and the effect on adhesion in epoxy composites

Carbon fibres with redox-active surface functionalities have shown potential applications in environmental remediation, and as burgeoning materials for structural batteries and super capacitors. In this work we describe the tethering of anthraquinone, capable of a reversible 2 electron transfer in aqueous medium, to the carbon fibre surface, and the corresponding effect on interfacial adhesion. The anthraquinone alone results in a >150% improvement in interfacial shear strength and the redox activity is preserved. Further to this, we then use this conductive film as a means to grow an acrylic acid polymer on top of the anthraquinone base layer, characterized by water contact angle, infrared spectroscopy, and depth-profiling X-ray photoelectron spectroscopy. This outermost layer imparts additional benefit to fibre-to-matrix adhesion and preserves the redox activity of the modified carbon fibers. This work demonstrates the ability to grow dual component and covalently-attached sizings to the carbon fiber surface, without compromising the inherent benefits of the underlying carbon fibers.

Study on thermal conductive epoxy adhesive based on adopting hexagonal boron nitride/graphite hybrids

The effect of hybrid filler on newly developed thermal conductive epoxy adhesive has been reported in this paper. The hybrid filler containing hexagonal boron nitride (h-BN) and graphite (Gr) with the mass ratio of 1:1 was loaded in to the epoxy resin with different wt% ratio (10:90, 20:80, 30:70, 40:60, 50:50 and 60:40). The corresponding thermal conductivity of adhesives was measured using guarded heat flow meter technique which enhanced up to 2.025 W/mK with the loading of 60 wt% of hybrid filler. Lap shear strength of the adhesive containing 40 wt% of hybrid filler was higher than the pristine epoxy resin thereby confirming reinforcing effect of hybrid filler into the epoxy matrix. Afterward, the shear viscosity of uncured epoxy resin filled with hybrid fillers were analyzed by using parallel plate rheometry. Strong shear thinning behavior was exhibited at higher hybrid filler loading. Further, lower loss factor and higher Tg values were observed with increase in the hybrid filler (h-BN/Gr) loading thereby confirming the higher cross linking density and lower mobility of epoxy chain. Thermal stability of hybrid Gr/BN–epoxy composite adhesives was studied using thermo gravimetric analyzer. Scanning electron microscopy confirmed the uniform deposition of hybrid filler on to the surface of epoxy resin.

Validation of carbon fibers recycling by pyro-gasification: The influence of oxidation conditions to obtain clean fibers and promote fiber/matrix adhesion in epoxy composites

This work aims at demonstrating, at a pilot plant scale, the potential of the pyro-gasification process to produce carbon fibers (CF) as secondary raw materials. The solid residue obtained upon pyrolysis of CFRP was characterized and oxidized, applying different process conditions to provide clean fibers. The same process was applied to virgin fibers, thus highlighting the protective action that char provides to CF during the oxidation step. The recovered fibers were used to produce new short fiber composites which, upon optimization of the mixing and curing conditions, were competitive with the performance of pristine fibers composites. Indeed, the oxidation leaves an oxygen rich surface which positively interacts with the epoxy resin, thus promoting adhesion without the requirement of an additional sizing process after the CFs recycling. These results provided sufficient validation of the recovered CF quality, thus leading to the scale up of the process to produce an integrated pyro-gasification semi—industrial plant.

Effect of Aging Process in Different Solutions on Kenaf Fibre Structure and Its Interfacial Adhesion in Epoxy Composites

Interfacial adhesion of kenaf fibres in epoxy composites was investigated using single fibre pull-out test. Several aged kenaf fibres were tested in this work. Two types of kenaf fibres were used in the work, those treated with 6% NaOH and those untreated kenaf fibres. Kenaf fibres were aged in engine oil, water, salt water, and diesel. The pull-out tests were performed using microtensile tests. The tests were performed at 1 mm/min loading rate. Scanning electron microscopy was used to observe the damage on the fibres and the effect of the treatment. The general results revealed that aging of the fibres reduced their strength and interfacial adhesion. Salt water showed the least effect on the strength of the fibres. At most cases, the breakage in the fibres is the main failure. In other words, there is no remarkable effect of aging on the interfacial adhesion since the most impact was on the structure of the fibres.

Friction Coefficient Displayed by the Scratch of Epoxy Composites Filled by Metallic Particles under the Influence of Magnetic Field

The wide use of epoxy composites as bearing materials in electronic appliances necessitates studying their frictional behaviour under the influence of magnetic field. Experiments were carried out to investigate the effect of magnetic field on the friction coefficient displayed by the scratch of epoxy composites filled by iron, copper and aluminium particles at different concentrations. It was observed that, for epoxy filled by the metallic fillers (iron, copper and aluminium), under the effect of the magnetic field, friction coefficient showed relative decrease then significantly increased with further increase of the intensity of the magnetic field. Besides, friction coefficient increased with increasing the content of the metallic fillers due to the decrease of the strength of the epoxy matrix. The values of friction coefficient displayed by epoxy filled by copper were lower than those observed for epoxy filled by iron. Filling epoxy by aluminium displayed lower friction coefficient than that observed for epoxy composites filled by iron and copper. This can be attributed to the charging of aluminium by positive charge when slid against steel. The resultant charge on the sliding surfaces was lower than that generated when epoxy was filled by iron and copper. In that condition, the adhesion of epoxy composites would be relatively weaker leading to the decrease of friction coefficient.