：Thermal fracture is a common problem in engineering. Traditional studies mainly addressed surface crack propagation, with limited research on 3D internal crack propagation. This paper uses the 3D-ILC method to fabricate 3D internal cracks of different positions within semi-disc specimens. Physical experiments, numerical simulations and fracture morphology analysis were conducted on the propagation of 3D internal cracks under non-uniform temperature fields. The results indicate the following: 1) In physical experiment, different crack propagation modes were observed in group A at different heights, including “n-shaped” and “u-shaped” cracks, while group B formed the “s-shaped” cracks. 2) In numerical simulation, the crack propagation length and deflection angle for crack tips on both sides are different of the same specimen in group B. The K Ⅲ of the internal cracks in group B cannot be overlooked, consistent with the location of the “lance-like” fracture observed in the physical experiments. 3) In fracture morphology, group A cracks have smooth fracture surfaces, which are mode I-II mixed cracks, while group B cracks show lance-like fracture, considered mode I-II-Ⅲ mixed cracks. The results provide an experimental and theoretical basis for the study of 3D internal crack propagation patterns under non-uniform temperature fields.

In order to analyze the fracture behavior of FRP-strengthened concrete beams under dynamic loads, three-point bending dynamic tests of FRP-strengthened concrete beam specimens with four different initial crack-depth ratios (0.2, 0.3, 0.4 and 0.5) were carried out in this paper. The crack propagation was quantitatively analyzed by acoustic emission (AE) technique and digital image correlation (DIC) method, and the toughening mechanism of FRP-strengthened concrete beam during crack propagation was studied. The test results show that, there are three key points in the failure process of FRP-strengthened concrete beams with cracks, which are the crack initiation point, crack resistance point and peak load point, respectively. The load values at the three key points of FRP-strengthened concrete beams with cracks decrease with the increase of initial crack-depth ratios. The location analysis of AE shows that the number of AE events can be used to indicate the crack width in the fracture process zone (FPZ) of FRP-strengthened concrete. The crack width of concrete beam specimens can be quantitatively determined by DIC and decrease with the increase of initial crack-depth ratios, indicating that observation results of DIC and AE technology are consistent, which is effective for characterizing the dynamic fracture behavior of concrete materials.