Fracture criteria, mixed mode

Concrete structure. Retrofitting, Carbon fiber sheet. Adhesive interface, Mixed mode. Fracture toughness. Fracture criterion... 

In the present work, a novel experimental method was proposed to evaluate the modes I-fll fracture toughness of the adhesive interface between concrete and carbon fiber sheets. The validity of the evaluation formula was studied on the basis of the results of finite element analysis. The mixed mode fracture toughness and fracture criterion of the adhesive interface were also studied on the basis of the results of fracture toughness test using the proposed method. 

The mixed mode fracture toughness tests were carried out on a universal testing machine at loading rate of 1 mm/min. The loading angle was varied to study the criterion of mixed mode fracture as = 0°, 15°, 30°, 90° (G /G=0.01, 0.31, 0.55, 0.95). 

In addition, the fracture toughness, G, of the present specimen was much lower than that of the adhesive resin itself This would be also the consequence that the microscopic fracture occurred in the concrete blocks. However, the mixed mode fracture toughness, G, approximately coincided with the linear fracture criterion, G,+ G = const., [17]. This result suggests that the principle of superposition was valid for the present specimen, which is very important conclusion for the structural design. 

The mixed mode fracture toughness of the adhesive interface followed the linear fracture criterion. This result suggests that the principle of superposition was valid... 

With Equation (8.21), we can define the mixed mode fracture toughness, Kc, using the G-criterion as [75]... 

It may be concluded that the results obtained confirm the data published previously by other authors. The values of Kj and for the same materials may be used in establishing a criterion for mixed-mode fracture in concretes. Soroushian et al. (1998) investigated the problems of mixed-mode fracture in concrete elements with steel and polypropylene fibres. Modes I (opening) and II (sliding) were considered and the conclusions supported application... 

Song, L., Huang, S. M., Yang, S. C. (2004) Experimental investigation on criterion of three-dimensional mixed-mode fracture for concrete, Cement and Concrete Research, 14 913-16. 

R. J. Niusmer, An Energy Release Rate Criterion for Mixed Mode Fracture, Int. J. Fracture, 10[3] 305 321 (1974)... 

Then, this criterion has to be applied to the CEPM with the pile-up formation. Considering the crack loaded in pure mode I, the inclined slip plane at the crack tip is loaded in mixed mode I+n (Fig. 5-57). The resolved local stress intensity factor (k) has components along the mode I and the mode II axes. The fracture criterion [Eq. (5-33)] is represented by the vertical line at ki-ki ... 

One aspect that arises with mixed-mode loading is that of deciding a fracture criterion. A possible first choice is ... 

In predicting whether or not a candidate polymer will be ductile, it is recommended to err on the conservative side, and not to propose that the polymer will prefer shear yielding to brittle fracture unless ar(T)>l. 2-ay(T), instead of using the criterion af(T)>ay(T) suggested by Figure 11.9 for preference for shear yielding. There are several reasons for such caution. Firstly, when df(T) and ay(T) are very similar at a given T, mixed ductile/brittle failure modes and statistical... 

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