Fracture toughness of mixed-mode anticracks in highly porous materials

• Published in: Nature communications 2024-09, Vol.15 (1), p.7379-11, Article 7379
• Main Authors: Adam, Valentin, Bergfeld, Bastian, Weißgraeber, Philipp, van Herwijnen, Alec, Rosendahl, Philipp L.
• Format: Article
• Language: English
• Subjects: 639/301/930/12; 704/4111; Benchmarks; Collapse; Compression; Field tests; Fracture toughness; Heat treating; Humanities and Social Sciences; multidisciplinary; Porous materials; Propagation modes; Science; Science (multidisciplinary); Shear; Snowpack; Structural failure
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-51491-7

When porous materials are subjected to compressive loads, localized failure chains, commonly termed anticracks, can occur and cause large-scale structural failure. Similar to tensile and shear cracks, the resistance to anticrack growth is governed by fracture toughness. Yet, nothing is known about the mixed-mode fracture toughness for highly porous materials subjected to shear and compression. We present fracture mechanical field experiments tailored for weak layers in a natural snowpack. Using a mechanical model for interpretation, we calculate the fracture toughness for anticrack growth for the full range of mode interactions, from pure shear to pure collapse. The measurements show that fracture toughness values are significantly larger in shear than in collapse, and suggest a power-law interaction between the anticrack propagation modes. Our results offer insights into the fracture characteristics of anticracks in highly porous materials and provide important benchmarks for computational modeling. Porous materials such as snow can collapse under compression, forming anticracks. The authors show that anticrack fracture modes vary with loading direction and find a mechanism that suggests that cracks grow more easily under compression than under shear, advancing stability models for porous materials.