Bridging effects in heterogeneous composite materials are traditionally treated as tractions lumped at the crack surface. This conventional equivalence, however, may fail to reveal the fundamental mechanisms of composite toughening. Hereby, a damage-plastic multiphase model is proposed and developed which is capable of capturing the engaging bridging mechanisms of fiber reinforced cementitious composites without the need for explicit representation of fibers. The key idea is to idealize the composites as the mixture of an activated fiber phase integrating all bridging fibers and an effective Cauchy continuum phase representative of the matrix and bonded fibers which interact through a nonlinear interface. The kinematics of matrix and fiber phases are independently described through the introduction of additional slip fields. This proposed modeling framework has the following novelties: (1) a new nonlocal slip theory is proposed which allows to depict the micro-slippage of arbitrarily distributed activated fibers with a minimum number of auxiliary kinematic descriptors, (2) a unified damage-plastic framework for the fiber–matrix interface is developed, enabling the method to characterize simultaneously the slip-dependent interface, fiber pull-out and fiber rupture, and (3) it is demonstrated that the composite toughening effect originates not only from interfacial friction but also from elasto-plastic stretching of fibers and pulley force actions, among which interfacial friction is the dominating energy absorbing mechanism. The proposed damage-plastic multiphase model is validated against experimental data from the single-fiber level and the structural level.

传统上，将异质复合材料中的桥接效应视为牵引力集中在裂纹表面。但是，这种传统的等效性可能无法揭示复合增韧的基本机理。因此，提出并开发了一种损伤塑性多相模型，该模型能够捕获纤维增强水泥基复合材料的啮合桥联机制，而无需明确表示纤维。关键思想是将复合材料理想化为包含所有桥接纤维的活化纤维相与代表基质和通过非线性界面相互作用的粘合纤维的有效柯西连续相的混合物。基质和纤维相的运动学通过引入额外的滑移场来独立描述。该拟议的建模框架具有以下新颖性：（1）提出了一种新的非局部滑移理论，该理论允许用最少数量的辅助运动学描述子描述任意分布的活化纤维的微滑移，（2）统一的损伤塑性框架为纤维-基体界面的开发，使该方法能够同时表征与滑移有关的界面，纤维拉出和纤维断裂，并且（3）证明了复合增韧作用不仅源自界面摩擦，而且源自纤维的弹塑性拉伸和滑轮力作用，其中界面摩擦是主要的能量吸收机制。从单纤维水平和结构水平的实验数据验证了所提出的损伤塑性多相模型。