Identification of fracture damage characteristics in ultra-high performance cement-based composite using digital image correlation and acoustic emission techniques

Abstract

The study of fracture mechanism and damage of ultra-high performance fiber reinforced cement-based composite (UHPFRCC) is of great significance for material performance evaluation and nondestructive structural health monitoring. In this paper, three-point bending fracture tests of UHPFRCC with fiber content of 1% and 2% were carried out, and the digital image correlation (DIC) and acoustic emission (AE) technique were used to monitor the fracture simultaneously. The microcrack area of UHPFRCC1 (UHPFRCC with 1% fiber content) decreases gradually with the loading process, and the microcrack area of UHPFRCC2 (UHPFRCC with 2% fiber content) increases first and then decreases with the loading process. The macrocrack area of UHPFRCC1 and UHPFRCC2 increases gradually with the same growth trend. The matrix failure and fiber/matrix debonding behavior of UHPFRCC were identified effectively based on the unsupervised k-means clustering method, and the fiber/matrix debonding behavior was obvious when the AE amplitude was greater than 60 dB. Meanwhile, the clustering results are also verified by the evolution of FPZ length. Finally, an efficient identification model of UHPFRCC matrix failure and fiber/matrix debonding behavior based on supervised KNN algorithm is proposed, which provides theoretical support for nondestructive structural health monitoring in practical engineering.