Monitoring Fracture Kinetics in Composite Materials Using Acoustic Emission Diagnostics

The structural-phenomenological concept (SPС) and model of the evolution of fracture in a composite material are considered. The relationship is explored between the bearing capacity and the kinetics of redistributing the weight composition of micro-, meso-, and macroscale damage during the loading process. Monitoring the change in the cumulative amount of partial damage values in the structure of a material at different scales in the loading mode and comparing these values with the threshold makes it possible to control the actual state of the load-bearing capacity of the product. The correspondence between the surfaces of micro-, meso-, and macrofractures of bonds in a structural material and energy parameters of the recorded acoustic emission pulses is theoretically substantiated and experimentally confirmed. The acoustic emission pulses are formed in the field of descriptors of the relative energy (E_p) and maximum amplitude (u_m) of the domains of the lower (L), middle (M), and upper (U) levels. The boundaries of these energy levels are as follows: E_p < 85 dB, u_m < 55 dB; E_p = 85 –115 dB, u_m = 55–80 dB; E_p > of 115 dB, u_m > 80 dB, respectively. An algorithm and software are developed to control the dynamics of the redistribution of the parameters of partial activity (N_i) and weight composition (W_i) of location pulses in energy domains that characterize the kinetics of micro-, meso-, and macrodamage in situ for breaking the structural bonds of the product in the loading mode. By comparing the current values of the most informative parameters W_L and W_M with the threshold values [W_L] and [W_M] corresponding to the product entering the stage of material failure, we can control the actual level of the bearing capacity of the structure. The developed concept, algorithm, and software are used to assess the load-bearing capacity of a panel with the frame structure during compression tests in the loading mode.