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In this study, we propose a new approach for the homogeneous liquid-phase transfer of graphene oxide (GO) into epoxy resin. This makes the process more efficient, while achieving fully uniform distribution of GO flakes within the epoxy matrix. Introduction of as little as 0.4% and 0.6% GO drastically increases the viscosity of the compositions, pointing at the highly exfoliated condition of GO in the resin. A significant accelerating effect of GO on the curing reaction is attributed to reactive groups on the GO surface. The study of the thermo-mechanical properties revealed that the introduction of relatively small amount of GO (0.2 wt%) into the epoxy matrix results in the increase of the storage modulus by 25.4% (3035 MPa) relative to the neat epoxy polymer (2420 MPa). The use of the high-temperature curing agent affords the composites with significantly higher glass transition temperatures, compared to the low-temperature curing agent, broadening the scope of their potential applications.

This paper demonstrates the effectiveness of parametrically-upscaled continuum damage mechanics (PUCDM) models for multiscale damage analysis of S-2 glass fiber/SC-15 epoxy matrix composite beams subjected to single-edge notched bending (SENB) tests. The SENB experiments with [ 0 12 / 9 0 12 ] double-ply and [ 0 8 / 9 0 8 / 0 8 ] triple-ply composite beams use synchrotron X-ray phase-contrast imaging for in-situ damage characterization. PUCDM models represent a class of thermodynamically-consistent multiscale constitutive models that bridge length-scales through explicit incorporation of representative aggregated microstructural parameters (RAMPs) in constitutive coefficients. Functional forms of RAMPs are generated through machine learning tools, operating on a micromechanical analysis database. The efficient PUCDM-based FE simulations reveal multiscale damage phenomena in the SENB experiments.

The purpose of this study is to further the search for the optimal conditions for the recovery of recycled carbon fiber (rCF) from epoxy matrix CFRP by thermal decomposition. We revealed that an oxidizing atmosphere was required to recover rCF. By investigating the strength reduction of CF after the heat treatment (hCF), it was demonstrated that significant strength reduction occurred at 600 °C. The damage also depended on the treatment temperature and time because of the oxidative decomposition of the fiber surface. By comparing the virgin CF, hCF and rCF, it was demonstrated that the strength reduction of the rCF was caused not only by the thermal oxidative decomposition but also by its interaction with the resin. Additionally, the time required to recover rCF differs depending on the treatment temperature and the degree to which each effect on the CF in CFRP depended on the location of the CF. At low temperatures, recovery time was longer, and the differences in strength between rCF recovered from the inner and outer layers were large. although CF recovery was quick at high temperatures, but the strength was significantly lower because of the effect of the interaction with the resin.

The bond characteristics of double strap joints between carbon fibre reinforced polymer (CFRP) laminates and steel with carbon nanotubes (CNTs) modified epoxy, under moderately elevated temperature (23–70 °C) were studied. The effect of CNTs on the failure modes, bond interface, and bond strength were presented. Results show that increasing test temperature causes transition of failure from epoxy-CFRP interface to steel–epoxy interface and to cohesive layer in the joints with neat epoxy. The cohesive failure could be avoided in the joints with CNT-epoxy. The observations from scanning electron microscopy revealed that CNTs bridge the cracks in epoxy matrix indicating a reinforcing effect. Moreover, CNT-epoxy can provide a significant increase (about two fold) of bond strengths at moderately elevated temperatures when compared with neat epoxy. It demonstrated that the incorporation of CNTs into the bond adhesive could allow better exploiting the potential of CFRP system in strengthening of steel structures at moderately elevated temperature.

In this study, E-glass fiber reinforced composites have been manufactured with two types of resin, polypropylene and epoxy (Thermoplastic and Thermoset) and they have been subjected to the low velocity single and repeated impacts and effect of resin type on the impact response of composites are investigated. Impact energies were chosen as 20 J, 50 J, 80 J and 110 J for single impact tests while 50 J was chosen for repeated impact tests. Comparisons between the results of 110 J single and 50 J repeated impacted specimens were performed. As a result of the study it is concluded that the resin type is a crucial parameter for the repeated impact response of the composites. (C) 2015 Elsevier Ltd. All rights reserved.

Inspired by biological systems in which damage triggers an autonomic healing response, a polymer composite material that can heal itself when cracked has been developed. In this work, compression and tensile properties of a self-healed fibre reinforced epoxy composites were investigated. Microencapsulated epoxy and mercaptan healing agents were incorporated into a glass fibre reinforced epoxy matrix to produce a polymer composite capable of self-healing. The self-repair microcapsules in the epoxy resin would break as a result of microcrack expansion in the matrix, and letting out the strong repair agent to recover the mechanical strength with a relative healing efficiency of up to 140% which is a ratio of healed property value to initial property value or healing efficiency up to 119% if using the healed strength with the damaged strength.

The increasing utilisation of carbon materials increases the waste generation. Therefore, it is necessary to analyse recycling alternatives. In this research, carbon powder wastes obtained from the cutting process of laminate composites have been incorporated into epoxy matrix phase in order to improve the mechanical characteristics. Physical and mechanical properties, hardness, abrasion, erosion and thermal behaviour have been analysed. Results show that carbon powder wastes incorporated to new epoxy matrix phases act basically as reinforcement. This allows for the recycling of the residues as well as improves some properties of the composites.

This paper deals with the investigation of the effect of carbon nanotube (CNT) waviness on the effective coefficient of thermal expansion (CTE) of a novel continuous fuzzy fiber reinforced composite (FFRC). This novel FFRC is composed of carbon fibers, sinusoidally wavy CNTs and epoxy matrix. The sinusoidally wavy CNTs are radially grown on the circumferential surfaces of the carbon fibers. Analytical micromechanics model based on the method of cells (MOC) approach is derived to investigate the influence of the waviness of CNTs on the effective CTEs of the FFRC. The present study reveals that if the amplitudes of the radially grown sinusoidally wavy CNTs are parallel to the axis of the carbon fiber then the thermoelastic properties of the FFRC are significantly improved over those of the FFRC being composed of straight CNTs.

An investigation is conducted on the effect of the hybrid of multi-wall carbon nanotubes (MWCNTs) and graphene oxide (GO) nanosheets on the tribological performance of epoxy composites at low GO weight fractions of 0.05–0.5 phr. The MWCNT amount is kept constant at 0.5 phr, which is typical for CNT/epoxy composites with enhanced mechanical properties. Friction and wear tests against smooth steel show that the introduction of 0.5 phr MWCNTs into the epoxy matrix increases the friction coefficient and decreases the specific wear rate. When testing the tribological performance of MWCNT/GO hybrids, it is shown that at a high GO amount of 0.5 phr, the friction coefficient is decreased below that of the neat matrix whereas the wear rate is increased above that of the neat matrix. At an optimal hybrid formulation, i.e., 0.5 phr MWCNTs and 0.1 phr GO, a further increase in the friction coefficient and a further reduction in the specific wear rate are observed. The specific wear rate is reduced by about 40% down to a factor of 11 relative to the neat epoxy when the GO content is 0.1 phr.

Amine-functionalized carbon nanofibers (A-CNFs) were deposited on the surface of individual sized carbon fibers using electrophoretic deposition (EPD), and the average interfacial shear strength (IFSS) was determined using the single fiber fragmentation test in conjunction with Weibull analysis. The IFSS decreased by 25% for fibers acting as the negative electrode in water without CNFs, and the impact of agglomerates on IFSS estimation is discussed. Further, a 187% IFSS increase was achieved for fibers undergoing a two-stage A-CNF EPD approach.

Mechanical properties of carbon fiber (CF) reinforced epoxy composites enhanced with a small quantity of multi-walled carbon nanotubes (MWCNTs) were investigated. 1 wt.% MWCNTs were well dispersed in the epoxy matrix and the CF prepregs were manufactured using fiber filament wind process. The hybrid MWCNT/CF/epoxy composites were fabricated by laying up of fiber prepregs. Tensile properties, interlaminar shear strength (ILSS) and microstructures of the composites were investigated. The results show that the addition of MWCNTs into the composites improved the tensile properties and ILSS with much reduced dispersity. Enhancing mechanisms behind these were elucidated.

The calendering approach has proved to be an effective alternative to chemical dispersion routes, but knowledge on the effectiveness of the different calendering parameters and methods used is still lacking. This study compared two different calendering methods widely used in the literature to evaluate possible differences in their dispersion effectiveness and their effect on the main properties of the nanocomposites being used. The nanocomposites’ thermal, electrical, mechanical and thermomechanical properties were evaluated to exhaustively analyze the influence of each calendering method on these properties. Slight differences were observed in the dispersion effectiveness of the two methods analyzed, and behavioral differences were found in the nanocomposites with high and low nanoreinforcement contents.

Kevlar fibres have been widely used as impact-resistant reinforcement in composite materials. However, there are very few works about the effects of nanoclays on the impact strength of Kevlar/epoxy laminates. Therefore, this paper intends to study the ideal amount of nanoclays to obtain the best impact performance. Nanoclays Cloisite 30B were dispersed in the epoxy system of at 1.5%, 3% and 6% in weight. For better dispersion and interface adhesion matrix/clay, nanoclays were previously subjected to a silane treatment appropriate to the epoxy resin. The laminates manufactured with epoxy resin filled by 6 wt.% of nanoclays shown the best performance in terms of elastic recuperation and penetration threshold. The opposite tendency was observed for the displacement at peak load. However marginal benefits can be found when compared the results obtained for laminates filled by 3% and 6% of nanoclays.

This paper proposes a new mathematical fracture model (FM) applicable to a biaxial reinforced composite material. The mathematical model provides predictions about the limit state of composite material. It is applicable both in uniaxial and biaxial requests. The mathematical model is validated by comparing its predictions with the experimental data obtained by authors. The studied composite material is composed by carbon fibre in epoxy matrix. The process used for obtaining the composite materials plates is vacuum forming.

Accepted: 2011-04-28, 資料番号: SA1003048000

Kevlar fibre/epoxy composites with superior interfacial strength were developed, by chemical treatment of the fibre surface with organic solvents. Multiple fibre pullout tests revealed that it is possible to raise the interfacial strength to 63 MPa from a value of 39 MPa normally exhibited by untreated Kevlar fibre/epoxy composites. A physicochemical and morphological characterization of the chemically treated fibre surface by microscopic and spectroscopic techniques, aids in the understanding of the observed interfacial properties. The importance of surface oxygen content in matrix bonding and mechanical interlocking of the fibre and matrix was established. Failure analysis of the pullout specimens reveals a strong correlation between the fracture features and the observed test data.