Biological composites can overcome the conflict between strength and toughness to achieve unprecedented mechanical properties in engineering materials. The suture joint, as a kind of heterogeneous architecture widely existing in biological tissues, is crucial to connect dissimilar components and to attain a tradeoff of all-sided functional performances. Therefore, the suture joints have attracted many researchers to theoretically investigate their mechanical response. However, most of the previous models focus on the sutural interface between two chemically similar stiff phases with (or without) a thin adhesive layer, which are under the framework of linear elasticity and small deformation. Here, a general model based on the finite deformation framework is proposed to explore the stiffness and toughness of chemically dissimilar suture joints connecting soft and stiff phases. Uniaxial tension tests are conducted to investigate the tensile response of the suture joints, and finite element simulations are implemented to explore the underlying mechanisms, considering both material nonlinearity and cohesive properties of the interface. Two failure modes are quantitively captured by our model. The stored elastic energy in the soft phase competes with the energy dissipation due to the interface debonding, which controls the transition among different failure modes. The toughness of the suture joints depends on not only the intrinsic strengths of the constituent materials and their cohesive strength, but also the interfacial geometry. This work provides the structure-property relationships of the soft/stiff suture joints and gives a foundational guidance of mechanical design towards high-performance bioinspired composites.

生物复合材料可以克服强度和韧性之间的冲突，在工程材料中实现前所未有的力学性能。缝合关节作为一种广泛存在于生物组织中的异质结构，对于连接不同的组件和实现全方位功能性能的权衡至关重要。因此，缝合关节吸引了许多研究人员从理论上研究其力学响应。然而，以前的大多数模型都集中在两个化学相似的刚性相之间的缝合界面，有（或没有）薄的粘合层，它们处于线性弹性和小变形的框架下。这里，提出了一种基于有限变形框架的通用模型来探索连接软硬相的化学异种缝合接头的刚度和韧性。进行单轴拉伸试验以研究缝合接头的拉伸响应，并实施有限元模拟以探索潜在机制，同时考虑材料的非线性和界面的内聚特性。我们的模型定量地捕获了两种失效模式。软相中储存的弹性能量与界面剥离引起的能量耗散竞争，从而控制了不同失效模式之间的过渡。缝合接头的韧性不仅取决于组成材料的内在强度及其内聚强度，还取决于界面几何形状。