Since fiber reinforced composites are often used in an aggressive environment (bridge decks, drainage pipes etc.), it is necessary to estimate their durability and ability to maintain superior mechanical properties in such conditions. One of microscale mechanisms that has a dominant influence on achieving desirable mesomechanical behavior, such as multiple cracking, is fiber-matrix interfacial bond. In the present study, the effect of calcium leaching on the bond properties and fiber-matrix interfacial one are experimentally investigated. To this end, a series of tests is performed, in which a single fiber is pulled out from cementitious matrix under displacement control. Both chemical and frictional bonds are calculated from the measured load-displacement curves, and the effect of environmental exposure on these parameters is clarified. In order to gain a deeper insight into the microscale mechanical phenomena associated with calcium leaching, the fiber-matrix interfaces of both control and chemically attacked specimens are examined by nanoindentation and ESEM. These experiments show that leaching severely degrades the stiffness of the farther transitional zone. and Obsahuje seznam literatury
Thioacetamide (TAA) is widely used in the production of drugs, pesticides and dyeing auxiliaries. Moreover, it is a chemical that can cause liver damage and cancer. TAA has recently been identified to cause bone damage in animal models. However, the type of bone damage that TAA causes and its potential pathogenic mechanisms remain unclear. The toxic effects of TAA on the femurs of New Zealand white rabbits and the underlying toxicity mechanism were investigated in this study. Serum samples, the heart, liver, kidney and femurs were collected from rabbits after intraperitoneal injection of TAA for 5 months (100 and 200 mg/kg). The New Zealand white rabbits treated with TAA showed significant weight loss and femoral shortening. The activities of total bilirubin, total bile acid and gamma-glutamyl transpeptidase in the serum were increased following treatment with TAA. In addition, the cortical bone became thinner, and the trabecular thickness decreased significantly in TAA-treated rabbits, which was accompanied by significantly decreased mineral density of the cortical and trabecular bone. Moreover, there was a significant decrease in modulus of elasticity and maximum load on bone stress in TAA-treated rabbits. The western blotting results showed that the expression of phosphorylated (p)-p38 and p-ERK in femur tissues of rabbits were increased after TAA administration. Collectively, these results suggested that TAA may lead to femoral damage in rabbits by activating the p38/ERK signaling pathway.