The fracture of core-shell particle reinforced composites was simulated using a crack phase field method. A pre-existing crack may grow along the interface between the core and shell (core debonding), may penetrate the shell and the core (trans-core fracture), or may grow in the matrix (brittle fracture in the matrix). Shell fracture behaviours resulting from the competition between the fracture resistance and fracture driving force are crucial to the crack growth mechanisms. It was found that moderate strength and low modulus of the shell favoured trans-core fracture, and low strength and high modulus of the shell favoured core debonding. The effects on the overall mechanical properties were also identified. The composite strength usually benefited from stiffer and tougher components, regardless of the crack growth mechanisms, while the composite toughness was more complex. The toughening effect was highly related to how the crack evolved, as core debonding improved the toughness at the significant cost of strength, and trans-core fracture contributed most to the toughness with a slight reduction in strength compared with the matrix. These findings indicate design strategies for epoxy composites which can achieve a balance of strength and toughness, enabling the design of safer lightweight composites for electric vehicles and transport applications.

中文翻译：

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核壳颗粒增强复合材料断裂的数值分析

采用裂纹相场法模拟核壳颗粒增强复合材料的断裂。预先存在的裂纹可能沿着核和壳之间的界面生长（核脱粘），可能穿透壳和核（跨核断裂），或者可能在基体中生长（基体中的脆性断裂）。由断裂抗力和断裂驱动力之间的竞争产生的壳断裂行为对于裂纹扩展机制至关重要。研究发现，中等强度和低模量的壳有利于跨芯断裂，低强度和高模量的壳有利于芯脱粘。还确定了对整体机械性能的影响。无论裂纹扩展机制如何，复合材料的强度通常受益于更硬和更韧的部件，而复合材料的韧性则更加复杂。增韧效果与裂纹的演变方式高度相关，因为芯部脱粘以显着的强度代价提高了韧性，而跨芯断裂对韧性的贡献最大，但与基体相比，强度略有下降。这些发现表明环氧复合材料的设计策略可以实现强度和韧性的平衡，从而为电动汽车和运输应用设计更安全的轻质复合材料。