EXPERIMENTAL EVALUATION OF THE EFFECT OF MOISTURE CONTENT AND SHEAR DIRECTION ON THE INTERFACE BEHAVIOR OF SAND AND FIBER REINFORCEMENT POLYMER

Carbon fiber polymer reinforcement sheets are available in two types of unidirectional and bidirectional woven sheets. Since the carbon fibers are one-directional tensile elements, any material produced from fibers will be anisotropic material. In this research, the anisotropy of the interface behavior between Carbon Fiber Polymer Reinforcements (CFRP) and sand was investigated at the laboratory. The main objective of this study was to evaluate the effect of the moisture content of the soil and the direction of the shear force on the interface behavior of sand and CFRP. The soil used in this study was a sandy silt collected from Joupar road in Kerman. Two types of CFRP sheets including unidirectional and bidirectional woven carbon fiber polymers were used in this study. The soil samples were prepared with different water contents ranging from 8.5 to 14.5% with a similar dry unit weight of 19.3 kN/m3. The direct shear test device with a modified shear box used to perform the interface shear tests under 50, 100, and 150 kPa of vertical stresses with 1mm per minute shearing rate. For unidirectional CFRP sheets, two series of parallel and perpendicular and for bidirectional CFRP sheets, two series of diagonal and parallel interface shear tests with different water contents of the sand were conducted. The results of these investigations showed that the interface behavior of sand and CFRP was anisotropic and was dependent on the direction of the shear displacement. For both unidirectional and bidirectional CFRP sheets, the interface friction angle was maximum when the shear direction was perpendicular to the fibers direction. The variation in the interface friction angle in the direction of the shear force in the unidirectional CFRP sheets was more considerable when compared to bidirectional CFRP sheets. The interface friction angle between sand and bidirectional CFRP sheets was larger than that between unidirectional sheets. Increasing the moisture content reduced the interface friction angle for both types of CFRP sheets; however, its reducing effect was much more considerable for unidirectional CFRP sheets.