2025-07-08 北海道大学,富山大学
（A）混合材料の破壊計算に用いるサンプル形状。
（B）混合材料における柔らかい要素の体積分率（φs）変化による応力―歪曲線の変化。柔らかい要素の体積分率が0.7の混合材料が延性破壊をしている。
＜関連情報＞
- https://www.hokudai.ac.jp/news/2025/07/post-1967.html
- https://www.hokudai.ac.jp/news/pdf/250708_pr.pdf
- https://www.pnas.org/doi/10.1073/pnas.2506071122
ソフト-ハード複合材料における基本的な強化メカニズム：最小限のフレームワークからの洞察 Fundamental toughening landscape in soft–hard composites: Insights from a minimal framework
Fucheng Tian, Katsuhiko Sato, Yong Zheng, +1 , and Jian Ping Gong
Proceedings of the National Academy of Sciences
DOI:https://doi.org/10.1073/pnas.2506071122
Significance
Nature presents a grand blueprint for material design by organizing soft and hard components into sophisticated multiscale and hierarchical architectures. Despite unprecedented progress, the most fundamental toughening mechanisms of soft–hard composite systems are yet to be fully understood, as most efforts have been devoted to emulating their complicated nonlinearities and structures. This work shows that a minimal soft–hard composite framework can achieve a transition from brittleness to toughness, yielding toughened composites that transcend their constituent phases. The findings unfold the fundamental toughening mechanisms of such systems and offer theoretical support for designing tougher materials.
Abstract
Soft–hard composite strategy is a highly general yet powerful approach to overcome the inherent trade-off between strength and toughness in material design. However, the underlying toughening mechanisms, veiled by nonlinearities and complex network interactions, remains unclear. Here, we employ a three-dimensional soft–hard composite (SH-com) framework by arranging randomly distributed linear-elastic soft and hard elements to explore the toughening mechanisms of soft–hard composites, while shielding the influence of complex nonlinearities and network architectures. Key features observed in soft–hard composites, including mechanical hysteresis, sacrificial bond-driven toughening, and brittle-to-ductile (BTD) transitions, are successfully reproduced, suggesting that the simplest model captures the essence of toughening in soft–hard composites. Visualization of internal fracture reveals distinct fracture patterns associated with the BTD transition, while numerical and theoretical analyses elucidate its mechanical origins. Furthermore, we identify an optimal toughening composition governed by a unified scaling relation linked to the fracture toughness ratio between soft and hard components. A fundamental toughening phase diagram is also established in terms of strength and toughness. This work sheds light on the underlying toughening landscape of soft–hard composite systems.
