Glass-fiber reinforced polymer (GFRP) composite rods with epoxy matrix filled with electrically nonconducting particles find widespread use in high-voltage electrical insulator applications. The service loads require a range of different, minimum material property values, e.g. toughness, tensile, or compressive strength, but also component-specific performance, e.g. pull-out friction of surface crimped metal fittings or electric breakdown strength. The contribution discusses selected examples of the effects of different particle filler types on the properties of filled epoxy resin as well as on the behavior of GFRP rods with such a matrix. In all investigated systems CaCO₃ was used as micron-sized filler, complemented by different amounts of either nanosilica or core-shell rubber (binary filler), or by both, nanosilica and core-shell rubber (ternary filler). With ternary filler combinations at a content of 36 wt%, fracture toughness G_IC was improved in nanocomposite epoxy plates and in GFRP rods by 60% and 100%, respectively compared to a matrix with 20 wt% CaCO₃ (used as reference system). The glass transition temperature Tg for some ternary systems dropped from 160 °C (for neat epoxy), to approximately 140 °C, the maximum allowed drop in Tg in view of requirements from further processing steps of the electrically insulating components. The ternary fillers yield transfer of the improvements of fracture properties from epoxy nanocomposite plates into the GFRP rods beyond that of the system with CaCO₃ filler only. Compressive strength of the GFRP rods was improved by about 20% only for the binary nanosilica and CaCO₃ filler, and was not significantly enhanced with the ternary systems. That combination, however, did not yield improvements in toughness beyond the CaCO₃-filled nanocomposite plates and rods. With the range of filler types and contents investigated here, it was hence not possible to simultaneously optimize both, fracture toughness and compressive strength of the GFRP insulator rods.

In the present study, fatigue performance of 6061-T6 and 6082-T6 commercially available extruded aluminum alloys in dry air and 3.5 wt% NaCl-saturated environment was investigated and compared. It was found that the aggressive chloride environment accelerated fatigue failure by up to an order of magnitude compared to laboratory air. Furthermore, alloy 6061-T6 shows more predictable fatigue life, having less scatter in its time to failure in a corrosive environment. The presence of localized pitting corrosion, particularly in Fe-rich intermetallic phases, provides initiation sites for fatigue cracks, leading to premature failure in both alloys. The corrosion fatigue cracks dominantly propagate through the grain interiors rather than along grain boundaries, indicating a tendency to transgranular crack propagation mechanisms. The effect of different loading frequencies (10 Hz and 0.2 Hz) on the corrosion fatigue life of 6061-T6 alloy showed a slightly enhanced fatigue life at the higher frequency. It was also found that alloy 6061-T6 was susceptible to pitting corrosion in NaCl-saturated environments with concentrations ranging between 0.5 wt% and 3.5 wt% without exhibiting significant changes in fatigue life.

This paper reviews the relevant literature and covers the main aspects of the environmentally assisted cracking of Al-Mg-Si-(Cu) alloys. Apart from a brief overview of the major microstructural and mechanical properties, it presents research results on the corrosion sensitivity and stress corrosion susceptibility of Al-Mg-Si alloys. Possible mechanisms of stress corrosion cracking and corrosion fatigue in aluminum alloys, such as anodic dissolution and/or interaction with hydrogen, are considered. A number of factors, including atmospheric or solution conditions, applied stress, and material properties, can affect these mechanisms, leading to environmentally assisted cracking. Specific attention is given to Al-Mg-Si alloys with copper, which may increase the sensitivity to intergranular corrosion. The susceptibility to both intergranular corrosion and stress corrosion cracking of Cu-containing Al-Mg-Si alloys is mostly associated with a very thin layer (segregation) of Cu on the grain boundaries. However, the effect of Cu on the corrosion fatigue and fatigue crack growth rate of Al-Mg-Si alloys has received limited attention in the literature. At the current state of the research, it has not yet been holistically assessed, although a few studies have shown that a certain content of copper can improve the resistance of aluminum alloys to the environment with regard to corrosion fatigue. Furthermore, considerations of the synergistic actions of various factors remain essential for further studying environmentally assisted cracking phenomena in aluminum alloys.

The long-term viscoelastic behaviour of epoxy matrices in Carbon Fibre-Reinforced Polymer (CFRP) tendons can lead to creep strains which must be accurately quantified to improve the current necessarily conservative design guidelines for bridge applications. However, the task of experimentally capturing such strains—typically in the range of 0.05%—requires sensors with reliable long-term accuracy and precision. This study investigates creep in CFRP tendons subjected to sustained tensile loading at 80% (for 7 days) and 88% (for 22 h) of their ultimate tensile strength. Four strain sensing techniques were employed to capture the creep strains of the CFRP tendons: bonded metal foil strain gauges, a contact extensometer, Digital Image Correlation, and distributed fibre optic strain sensing. This work precisely quantifies—for the first time in CFRP creep testing—the influence of experimental artefacts on the performance of the strain sensors, including test rig movement, temperature sensitivity, and localised surface inhomogeneities. Results reveal significant measurement distortions: the extensometer recorded strain increases of 250% during tendon slip, while distributed fibre optics detected localised strain peaks reaching 150% of the surface average. These findings demonstrate that sensor-induced noise can substantially contaminate creep strain data, underscoring the critical need for rigorous experimental protocols and thorough sensor validation in CFRP creep studies.

It was shown previously that cyclic loading can be used to extend the fatigue life of sheet plastic materials subjected to the preliminary impact-oscillatory loading. This type of loading causes dynamic non-equilibrium processes (DNP) in materials, which lead to the formation of dissipative structures in materials and on their surface. The density of these dissipative structures is less than that of the base metal. In this paper, the results of investigations into the relief and hardness of surface layers modified by impact-oscillatory loading are analyzed on the example of five structural materials. The signs of a regular, orderly system of microextrusions formed on flat surfaces of all materials due to DNP are considered along with the alignment of roughness parameters R_z and R_a of relief profiles. The effect of impact-oscillatory loading is one of the main causes that lead to the extension of the fatigue life of materials.