Research On Fracture For ?-? Mixed Mode Crack Of Aligned Steel Fiber Reinforced Cementitious Composite

The reinforing effect of steel fiber on cement matrix is affected by fiber distribution and orientation,aligned steel fiber reinforced cementitious composite not only fiber utilization rate is high,the fiber specific environment enhancement effect fully.Its inhomogeneous anisotropic or force in actual structure,mixed mode crack is more common.The fracture test for ?-? mixed mode crack of aligned steel fiber reinforced cementitious composite?ASFRC?and steel fiber reinforced cementitious composite?SFRC?were conducted.the numerical simulation of the whole process of SFRC were carried out by extended finited element method?XFEM?.The main research contents are as follows:?1?The whole fracture process of the three point bending beam with straight partial crack for ?-? mixed mode crack of ASFRC and SFRC were studied,the fracture parameters,the influence of enhancement of crack initiation angle and crack propagation were analyzed.The results showed that,the fracture characteristics of ASFRC was significantly greater than that of SFRC.The crack initiation angle and peak load gradually increased and fracture energy gradually decreased with the increase of the crack center offset distances,the enhancement of ASFRC were reduced with the increase of crack initiation angle.?2?The three-point bending beam of ASFRC and SFRC fracture tests with different crack positions based on the extended finited element method were simulated.The crack propagation trajectory,displacement nephogram were analysed,the validity and the simulation results were verified by comparing the P-CMOD curves.Show that the curves obtained by this method were in good agreement with the experimental results,it can be used to simulate the cracking of SFRC.?3?The fracture test for ?-? mixed mode crack of steel fiber reinforced cementitious composite?SFRC?with different the ratio of initial crack length and specimen depth?and fiber volume fraction?were simulated by XFEM.The P-CMOD curve,P-?curve were obtained,the effect of the ratio of initial crack length and specimen depth?and fiber volume fraction?on the P_max and the cracking angle were analyzed.The results showed that,with the increase of the fiber volume fraction,the P_max increased obviously and the critical point of P-CMOD curve gradually after the shift,the critical crack mouth opening displacement increased gradually;the?have a relatively large impact on the P_max,the greater?,fracture process zone the crack was shorter,the P_max was smaller.The ratio of initial crack length and specimen depth?in the range of 0.2⁰.4,initiation angle increases with the increase of crack depth ratio,and?is 0.5,the crack initiation angle decreases.When the specimen offset distance is large,the crack initiation angle with the increase of fiber volume increases.