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
The correct determination of material properties of construction materials from experiments is important not only during their development, but also during final verification. Specimens for testing mechanical properties of fiber-reinforced composites with a quasi-brittle matrix are usuall prepared by casting into a sutable mold. But they can be also prepared by cutting to desired shape from large body of material. The method of preparation may affect the measured values of material characteristics. In the case of sawed specimens, the fibers in surface layer are damaged, while in the case of casted specimens, fibers in surface layer tended to align with mold surface. The purpose of this article is to clarify the influence of these phenomena using numerical simulations. and Obsahuje seznam literatury