Thermomechanical Characterization of CFRPs under Elevated Temperatures for Strengthening Existing Structures

Fiber-reinforced polymers (FRP) are rapidly gaining acceptance from the construction sector due to their large effectiveness. They are mainly used as confining reinforcement for concrete columns and as tensile reinforcement for concrete beams, columns and slabs. FRPs are already used to a large extent for applications such as bridges and parking lots, where elevated temperatures are not the main risk. Their increasing use as structural reinforcement is hampered by the concern related to their behavior at elevated temperatures as the relevant research is deficient. Thanks to the significant advantage of FRPs’ mechanical properties, further investigation into the influence of heating on their mechanical behavior may solve many doubts. The present study examines the influence of temperatures, ranging among 50, 100 and 250 °C, on the tensile strength of FRP laminates with carbon fibers (CFRP). In addition, the resistance of CFRP specimens to low-cycle thermal loading at the temperatures of 50, 100 and 250 °C under constant tensile load was investigated. The experiments were carried out in the laboratory of Experimental Strength of Materials and Structures of Aristotle University of Thessaloniki.

Features of Thermomechanical Stability of Anionic–Cation Exchange Matrix “Polikon AC” on Viscose Non-Woven Materials

The thermomechanical stability of the anion–cation exchange matrix “Polikon AC” on viscose nonwoven materials is investigated. In this work, a molecular model of a solvation environment for experimentally obtained “Polikon AC” mosaic membranes is refined. Mosaic membranes on a viscose fiber base were fabricated by the method of polycondensation filling. The temperature dependence of deformation was investigated for dry and wet anion and cation exchange membrane components at a constant tensile load of 1.5 N and a heating rate of 8 °C/min. The effect of moisture content on the deformation of anionite and cationite fragments under a constant external tensile load of 1.5 and 3 N in a temperature range up to 100 °C was studied.

Shearography as a tool to measure creep strain in sealing elastomers

In this work, a new application of digital speckle pattern shearing interferometry (shearography) for strain measurement is proposed. This optical technique is implemented to measure strain in elastic materials. Three different sealing elastomers were tested in short-term creep tests in order to assess creep compliance, which is an important mechanical property for viscoelastic materials. The creep tests were carried out applying a constant tensile load to a specimen. An in-plane shearography setup was implemented to measure the creep strains in the polymers. Results of creep strains were compared with that obtained with a commercial equipment of digital image correlation (DIC). Although some limitations were found for shearography, it was possible to verify the adaptability of this technique for strain measurement in elastomers.