Polymer nanocomposites are binary systems consisting polymer as matrix and nanofiller as reinforcement. Understanding the fracture behavior of material is important to design and optimize the performance of nanocomposites. Most studies made so far investigated the failure behavior of nanocomposites by observing the fractured surface of material. This method was unable to reveal the generation and propagation of cracks in the nanocomposites subjected to the external load.

　　A team led by Professor Peng-Cheng Ma in the Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, reported the fracture behavior of polymer-based nanocomposites reinforced by carbon nanotubes (CNTs). In order to solve the problem associated with the dispersion and re-agglomeration of CNTs, three dimensional CNT sponge was prepared and incorporated into the epoxy through the monomer infusion process. The researchers used different techniques to characterize the performance of the obtained nanocomposites, and found that the fracture toughness and critical energy release rate of the material were enhanced by more than 100% and 250%, respectively. The toughening mechanism behind such observation was demonstrated by studying the in-situ crack initiation and propagation in the bulky nanocomposites with assistance of micro-mechanical testing device in a scanning electronic microscope chamber (Figure 1). The results demonstrated that the intrinsic fracture behaviors, such as void generation, as well as the extrinsic toughening features arising from crack deflection and bifurcation, were responsible for the improved fracture properties of nanocomposites.

　　Fig.1 In-situ observation of crack generation and propagation in epoxy matrix (A) and corresponding nanocomposites.

　　 This project was supported by the Western Light Foundation of Chinese Academy of Sciences (2019-XBQNXZ-B-010), and the Program for Attracting High-Level Talents in Xinjiang Uyghur Autonomous Region.

　　Paper information:

　　Ma Q, Hao B, Ma PC. In-situ characterization on the fracture behavior of three dimensional polymer nanocomposites reinforced by CNT sponge. Composites Science and Technology, 2022, 217, 109132 (Link).