A pull-out equivalent telescopic layered failure model of carbon fiber bundles in seawater sea-sand cementitious matrix

Based on the excellent mechanical properties and piezoresistive effect of carbon fiber, carbon fiber reinforced cementitious matrix (CFRCM) has been used in the strengthening and self-monitoring research of reinforced concrete (RC) structures. In this study, the assumptions of the telescopic layered model theory of CFRCM were refined. The factors influencing the piezoresistive effect of carbon fibers were subsequently analyzed. Simultaneously, the resistance calculation theory for the pull-out process of CFRCM bundles was established by combining the parallel circuit theory. Based on the above theories, a pull-out equivalent telescopic layered failure model of carbon fiber bundles in the cementitious matrix was developed, considering the trilinear cohesive material law (CML) and the piezoresistive effect. Pull-out tests on carbon fiber bundles in both freshwater standard sand and seawater sea-sand matrices were conducted. This model was successfully used to simulate the piezoresistive effect during the pull-out process of CFRCM bundles with two matrices and different embedded lengths. The number of fiber filaments in each layer, the rupture damage of the fiber filaments during the loading process, and the degree of matrix infiltration into the carbon fibers were calculated. This work lays the foundation for advancing the development of structural strengthening and structural health monitoring. •The telescopic layered failure model has been modified.•The resistance calculation theory of CFRCM has been proposed.•A full process failure analysis of CFRCM based on the piezoresistive effect has been achieved.