Energy-based versus stress-based material failure criteria: The experimental assessment

Previous studies have reported fracture localization within the inclusions of 3D-printed staggered composites, despite their significantly higher strength compared to the matrix – a seemingly counterintuitive phenomenon. In this letter, we investigate whether material failure is governed by the volumetric energy of fracture rather than the maximum stress criterion. We perform experiments on the constituent phases of 3D-printed staggered composites to evaluate the validity of energy-based failure criteria. Our findings support the idea that the work of fracture, rather than strength, governs failure. Specifically, at relatively higher strain rates, the ability of the soft matrix to absorb more energy before failure suggests that fracture localization is driven by energy considerations rather than stress thresholds. This aligns with previous observations that inclusions may fail before the matrix despite their higher strength. More broadly, since engineering materials often exhibit a crystalline molecular structure where failure is dictated by the energy required to break atomic and molecular bonds, it naturally follows that the work of fracture – rather than strength – should serve as the primary failure criterion. Our results reinforce this perspective, offering a more physically grounded approach to predicting material failure.