Investigation into dynamic fracture toughness of rigid insulation tile materials ranging from 78K to 1423K

Abstract

This work utilizes an enhanced elevated-temperature split Hopkinson pressure bar (SHPB) experimental system to perform three-point-bending (3-p-b) tests on rigid insulation tile (RIT) materials with a porosity of ∼87 %, assessing fracture toughness across a range of extreme temperatures spanning from 78 K to 1423 K. Based on the regulation of temperature change on fiber spacing and the influence of inertia effect, the application of boundary effect model (BEM) in dynamic elevated-temperature environment is expanded. Moreover, the experimental results indicate that the fracture toughness of RIT materials significantly dependent on temperature and loading rate. For example, from 293 K to 78 K, the fracture toughness at various loading rate increased significantly, with a maximum increase of ∼34.69 %. The temperature rises to the viscous-brittle transition temperature (∼973 K). Viscous flow and micro-crack self-healing lead to a significant increase in fracture toughness from 973 K to 1173 K at various loading rates, with an increase of more than 25.97 %. Near the raw material firing temperature (∼1473 K), the dominant fracture mode of fiber compaction and softening changed fundamentally, resulting in a significant decrease in fracture toughness at various loading rates, with a maximum decrease of 33.77 %. The fracture analysis results show that the significant difference in crack propagation mode and fiber fracture mechanism causes the loading rate sensitivity of fracture toughness. These findings will provide an important reference for evaluating the fracture properties of RIT materials under extreme temperature and high loading rate scenarios.