Papers by Author: Ali Ahmed Benyahia

Abstract: The aim of this work is the study of the long term behaviour of a laminated composite made in glass/polyester and aged in seawater at various temperatures. The results obtained show that the immersion in seawater causes ageing of the composite material. This was reflected first by a change in color of the material depending on the temperature of the immersion and the gel-coat loses its brightness. The infrared spectroscopy has confirmed activation of chemical degradation (hydrolysis of the resin and of the fibre/matrix interface, fibre degradation). This chemical degradation could be the cause of decrease in strength and ductility detected by analysing the behaviour of immersed testing specimens. It could also be the cause of the increase of absorption rate recorded for immersions exceeding 22 days.

Abstract: High-performance concrete (HPC) are advanced materials used in advances applications such as tunnels or nuclear power plant in which they can be accidentally submitted to severe stress or thermal conditions. The present study deals with the material response to thermal loading conditions. The main objective of this research is the characterization of the fracture toughness under Mode I at high temperature of high performance mortars by using notched specimens in three-point bending test in accordance with the RILEM recommendations. The mechanical loading is applied to the specimens while heated at various temperatures ranging from 25 to 900°C in isothermal conditions. The maximum applied load is found to be maximum at 300°C temperature and then to decrease sharply at higher temperatures. Analysis of SEM micrographs undertaken on the heated specimens after mechanical tests helps in the understanding of the material macroscopic behaviour. The evaluation of the material toughness during the hot testing is undertaken through analytical approach based on Fracture Mechanics. Lastly, the stress intensity factor as well as the energy of fracture evolves similarly versus temperature as the maximum applied load.