Knitting interloops one-dimensional yarns into three-dimensional fabrics that exhibit behaviours beyond their constitutive materials. How extensibility and anisotropy emerge from the hierarchical organisation of yarns into knitted fabrics has long been unresolved. We sought to unravel the mechanical roles of tensile mechanics, assembly and dynamics arising from the yarn level on fabric nonlinearity by developing a yarn-based dynamical model. This physically validated model captures the fundamental mechanical response of knitted fabrics, analogous to flexible metamaterials and biological fiber networks due to geometric nonlinearity within such hierarchical systems. Fabric anisotropy originates from observed yarn-yarn rearrangements during alignment dynamics and is topology-dependent. This yarn-based model also provides a design space of knitted fabrics to embed functionalities by varying geometric configuration and material property in instructed procedures compatible to machine manufacturing. Our hierarchical approach to build up a knitted fabrics computationally modernizes an ancient craft and represents a first step towards mechanical programmability of knitted fabrics in wide engineering applications.

翻译：针织工艺将一维纱线互连成三维织物，其表现出的特性超越了构成材料的固有属性。纱线在针织物中的层次化组织如何产生延展性与各向异性，这一长期未解之谜亟待破解。我们通过建立基于纱线的动力学模型，旨在揭示纱线层级的拉伸力学、组装与动力学对织物非线性的影响机制。该经物理验证的模型可捕捉针织物的基本力学响应，其几何非线性特征与柔性超材料及生物纤维网络相似，皆源于此类层级系统。织物的各向异性源于对齐动力学过程中观察到的纱线间重排现象，且具有拓扑依赖性。该基于纱线的模型还提供了针织物的设计空间，可通过在兼容机器制造的标准化流程中调整几何构型与材料属性，将特定功能嵌入织物。这种通过计算方法构建针织物的层级化方法，为古老工艺注入了现代活力，标志着向实现针织物在广泛工程应用中的力学可编程性迈出了第一步。