In this paper, the Mixed mode experimental results of 24 notched beams of concrete with various notch depths and locations are reported. The test results for conventional critical stress intensity factors and crack trajectories are demonstrated. It is noted that with the larger thickness, which results in conditions closer to plane strain, the crack path can be better predicted by linear elastic fracture mechanics criteria. The effects of applied load and specimen weight on the fracture are considered with the use of separate stress intensity factors. It is observed that the final failure angles, based on the crack path's intersection point with the beam's top side, are better predicted than the crack initiation angles, from the maximum principal stress criterion. Conventional Mixed mode fracture toughness increases with an increase in the mode II to mode I stress intensity factors ratio.

A two dimensional finite model with inclined crack at different crack angles are being analyzed in Mixed mode condition using photo elasticity method for the determination of Stress Intensity Factors. The well-known Sih’s equation and three points deterministic approach is used for the determination of stress intensity factors. The effects of biaxial load factor, crack angle, size factors were studied and a regression model was developed for geometry correction to predict Stress Intensity Factors. The results give a good compromise to the theoretical one. The experimental result also gives significant data for the two dimensional Mixed mode loading conditions.

The linear elastic fracture phenomenon has been characterized with stress intensity factors (SIFs). In this study a general function is obtained in order to predict the fracture parameters. Numerical calculation of the SIFs in a Mixed-mode condition is a cumbersome task. In this research, more than 6800 numerical analyses using extended finite element method are conducted to simulate the fracture problem. States are considered for a plate with an arbitrary edge or center crack. Mixed mode SIFs were calculated using of interaction integral. Then, Gene Expression Programming (GEP) method is utilized to extraction of a function. Results show acceptable correlations between numerical calculations and genetic programming functions. R-square (R2) values are in a range of 0. 91 to 0. 96 that guarantees the accuracy of the inferred functions.

In the case of explosions and fires, the rocks undergo a cycle of heating and cooling. For that, first, they are exposed to considerable heat and then cooled after extinguishing the fire. Temperature variations and subsequent contraction and expansion affect the physical and mechanical properties of rocks. Through two series of tests, the effects of temperature and the number of heating-cooling cycles on the mode I, mode II and the effective Mixed-mode I-II fracture toughness of Lushan sandstone were investigated. In the first series, the effect of temperature was studied in a heating– cooling cycle at ambient temperature (25° C) and 60, 150, 200, 300, 500, and 700° C. The highest and lowest mode I, mode II and the effective Mixed-mode I-II fracture toughness were, observed at 150 and 700° C, respectively. In the second series of tests, the effect of the number of heating– cooling cycles was investigated on the mode I, mode II and the effective Mixedmode I-II fracture toughness of sandstone specimens at 150° C (for hydraulic fracturing modeling) and a crack inclination angle of 45° . According to the results, the mode I, mode II and the effective Mixed-mode I-II fracture toughness increased in the first cycle and decreased with increasing the number of heating– cooling cycles. As the crack inclination increased, the effective Mixed-mode I-II fracture toughness of the sandstone specimens increased. The mode II fracture toughness increased up to a crack inclination angle of 45° and then decreased. Moreover, the mode of fracture changes from opening mode (mode I) at the crack inclination angle of zero degree to Mixed mode (tension-shear) at the crack inclination angle of less than 28. 8° . The mode of fracture changes from tensile-shear to compression-shear at the crack inclination angle of greater than 28. 8° .

Failures in composite materials occur mainly due to interlaminar fracture, also called delamination, between laminates. This indicates that characterizing interlaminar fracture toughness is the most effective factor in the fracture of composite materials. This study reports investigation on Mixed-mode interlaminar fracture behaviour in woven carbon fibre/polyetherimide (CF/FEI) thermoplastic composite material based on experimental and numerical analyses.Experiments were conducted using the special test loading device. By varying the loading angle,α from 0º to 90º, pure mode-I, pure mode-II and a wide range of Mixed-mode data were obtained experimentally. Using the finite-element results, geometrical factors were applied to the specimen. Based on experimentally measured critical loads, Mixed-mode interlaminar fracture toughness for the composite under consideration determined. The fracture surfaces were examined by scanning electron microscopy to gain insight into the failure responses.