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In this paper, a novel hemispherical microbond specimen is proposed for evaluating the interfacial shear strength of fiber-reinforced composites. A hemispherical microbond specimen was developed with the insertion of a pin-holed, Teflon film into a droplet matrix surrounding a single fiber. This experimental test offered more reliable strength data in the hemispherical specimen. Thus, the hemispherical microbond specimen is recommended to be suitable for evaluation of interfacial shear strength as a convenient alternative for the cylindrical pull-out test.

To evaluate mechanical performances of the transverse rib bar and reveal anchoring mechanism between the grout and steel bar, a series of pull-out tests were carried out, the numerical simulations and theoretical analysis of grout failure modes were also analyzed. Results show that the grout in front of the transverse rib display wedge-shape damage and the simulation results verify this damage forms. The formula of the effective transverse rib angle, the grout strength and anchorage force were derived based on elastic thick-wall cylinder theory. During the pull-out tests, the radial stress of the grout lagged the tangential stress reaching the ultimate tensile strength with the inner pressure increasing. The anchoring force of the transverse rib bar increases with the increase of the grout strength, and with the increase of the effective transverse rib angle. These conclusions provide the theoretical basis and technical support for the engineering practice.

Numerical analysis is carried on for the pull-out test of single fiber by ANSYS. Using bond-slip relationship between fiber and cement matrix obtained by test, the bond stress and its distribution of the fiber and cement matrix is studied, and the characteristics of the bond and debond part is obtained by calculating. Finite element analysis shows that fiber stress is transferred to the fiber embedded side as the fiber carrying the pullout force. When the pullout force is smaller, bond stress of fiber-mortar takes the form of a triangle or trapezoid; when it is maximum, bond stress is at maximum. The maximum pullout force calculated by FEM differs by 9.02% from experimental data, and the calculated value of pullout displacement at the pullout side differs by 7.43%∼12.37% from the experimental data. The calculated values are in good agreement with experimental.