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In the present study, an anodizing process was applied to aluminum alloy (AA2024-T3) to enhance interlocking in dissimilar joints with glass fiber-reinforced polyetherimide (GF/PEI) composite, using ytterbium-doped laser fiber welding as a heat source. A factorial Central Composite Design (CCD) was conducted to determine the most appropriate processing and optimization parameters, with lap shear strength (LSS) as the response variable. The obtained and fractured joints were characterized. Anodizing effectively improved the interlocking between dissimilar joints, resulting in LSS values of around 16 MPa. Surface impressions were observed in joints with lower shear values, likely due to the ineffective heat distribution in the processed joint. In the AA2024-T3 alloy, the annealing process occurred, beginning with the segregation of the alloy elements at the grain boundaries and subsequently reducing its hardness. The SEM analysis of the laminate in the best welding condition revealed a well-established fracture surface, with cusps, fibers covered by the polymer matrix, and river marks, indicating good consolidation of the process applied to the metal/polymer junction, which is consistent with the highest shear values obtained. These findings have important implications for future research and industrial applications and can help advance the understanding of these materials and processes. [ABSTRACT FROM AUTHOR]

Poly(ether-imide) (PEI)-based composites filled with multiwalled carbon nanotubes in a dispersed form (1.0 wt%) and as buckypaper (BP) (25 wt%) have been prepared by mixing solution and hot compression molding technique, respectively. Vacuum filtration technique with the aid of water-based surfactant Triton X-100 was employed to produce BP sheets. The thermal stability of the composites was evaluated by thermogravimetric analysis and revealed a strong increase in thermal degradation temperature when BPs were used as nanofiller. Ozawa–Wall–Flyn model was used to determine the kinetic parameters. It was observed an increase in activation energy as the nanotubes concentration rise, suggesting the formation of more thermally stable systems. In addition, half-life time as function of temperature demonstrated that BP-based composites could operate for 3200 years at 200°C. These results concluded that carbon nanotube BP could contribute to improve significantly the thermal stability of PEI matrix. [ABSTRACT FROM AUTHOR]

Polyphenylene sulfide-based nanocomposites filled with unmodified multiwalled carbon nanotubes from 0.5 wt% to 8.0 wt% have been prepared by melt mixing technique with a single-screw extruder and hot press. Transmission electronic microscopy and scanning electron microscopy analysis were carried out in order to assess the multiwalled carbon nanotubes dispersion throughout the polyphenylene sulfide matrix. Electrical conductivity of the polymer was dramatically enhanced by about 11 decades between 2.0 wt% and 3.0 wt% of nanotubes, suggesting the formation of three-dimensional conductive network within the polymeric matrix. The storage modulus (G′) of neat polyphenylene sulfide presented an increase by two orders of magnitude when 2.0 wt% of pristine multiwalled carbon nanotubes was considered, with the formation of an interconnected nanotube structure, indicative of “pseudo-solid-like” behavior. In addition, percolation networks were formed when the loading levels achieve up to 1.5 wt% for multiwalled carbon nanotubes/polyphenylene sulfide composites. [ABSTRACT FROM AUTHOR]

The use of thermoplastic composite materials in aerospace and naval fields has increased due principally to their high performance associated with low specific weight. In order to screen material behavior, the effects of external environments on the mechanical properties during usage must be clearly understood. Environmental factors such as ultraviolet radiation (UV), corrosive fluids, moisture and temperature can limit the applications of composites by deteriorating the mechanical properties over a period of time. In order to characterize composite materials, are commonly used tensile tests. Another test that can be used in order to evaluate the viscoelastic properties of thermoplastic composite materials is free vibration damping. In this work, the viscoelastic properties of polyamide 6.6/carbon fiber laminates were obtained by two types of tests: tensile and free vibration damping tests. Two families of textile polyamide/carbon fiber composites ([±45] and [0/90]) were obtained by hot compression molding. The present studies have been performed to explore relations between the dynamic mechanical properties and the influence of high moisture concentration of this thermoplastic laminate. The results show that the E' decrease with the increase in the exposed time for polyamide/carbon fiber composite specimens and that free vibration damping technique can be used instead of tensile test in order to know the elastic modulus. [ABSTRACT FROM AUTHOR]

This article reports on the experimental characterization of the fatigue behavior of GLARE laminate taking into account the hygrothermal effects. The environmental factors can limit the applications of composites by deteriorating the mechanical properties during service. The importance of temperature at the time of conditioning plays an important role in environmental degradation of such composite materials. In this work, the experiments showed that the hygrothermal conditioning can induce significant changes in the material properties. Due to the effect of the hygrothermal aging, both the tensile and fatigue values of the studied systems have been reduced, that is, the absorbed moisture has deleterious effects on the physical properties of metal-fiber composite laminates. [ABSTRACT FROM AUTHOR]

The increasing demand for electrical energy and the difficulties involved in installing new transmission lines presents a global challenge. Transmission line cables need to conduct more current, which creates the problem of excessive cable sag and limits the distance between towers. Therefore, it is necessary to develop new cables that have low thermal expansion coefficients, low densities, and high resistance to mechanical stress and corrosion. Continuous fiber-reinforced polymers are now widely used in many industries, including electrical utilities, and provide properties that are superior to those of traditional ACSR (aluminum conductor steel reinforced) cables. Although composite core cables show good performance in terms of corrosion, the contact of carbon fibers with aluminum promotes galvanic corrosion, which compromises mechanical performance. In this work, three different fiber coatings were tested (phenol formaldehyde resin, epoxy-based resin, and epoxy resin with polyester braiding), with measurements of the galvanic current. The use of epoxy resin combined with polyester braiding provided the best inhibition of galvanic corrosion. Investigation of thermal stability revealed that use of phenol formaldehyde resin resulted in a higher glass transition temperature. On the other hand, a post-cure process applied to epoxy-based resin enabled it to achieve glass transition temperatures of up to 200 °C. [ABSTRACT FROM AUTHOR]