多尺度模型下自修复沥青路面中微胶囊力学分析

Mechanical analysis of microcapsules in self-healing asphalt pavement based on multi-scale model

为研究自修复型沥青路面中微胶囊的力学行为,应用离散元法从宏观、细观和微观三个尺度逐层确定模型和参数,构建了含微胶囊的沥青路面多尺度模型,分析了车辆重载作用下微胶囊的受力状况。然后,建立了单个微胶囊有限元分析模型,分析了囊壁和囊芯在机械力作用下的应力及位移分布;根据第一强度理论,找出了微胶囊最易破坏的位置,确定了微胶囊在沥青路面中需满足的抗裂性能要求。研究表明,在1.43MPa轮胎接地压力下,沥青混凝土中面层沥青砂浆内部的接触压力和接触拉力分别为0.347N和0.093N。通过微观尺度的分析可得,微胶囊的所受接触压力的均值为25mN,接触拉力为7.7mN。对单个微胶囊的有限元分析可得:在微胶囊受压区域主要为压应力的承载区域;受压区域附近位置,在垂直于厚度方向上承受较大的拉应力,并出现了第一强度理论主应力峰值,很可能为微胶囊最先开裂的位置,且从囊壁外侧开始破裂。

Microcapsules made of polymer composites were found to be an effective additives for self-healing of asphalt concrete pavements, however, the self-healing mechanism and multi-scale modeling of microcapsules in asphalt mixtures has not been completely understood. In this study, a multi-scale model for asphalt pavements with microcapsules is established, from macro to meso and then to micro-scale, using the discrete element method. The mechanical responses of microcapsules are analyzed under simulated heavy traffic load. Then, a mechanical modelof a single microcapsule is established using finite element method(FEM) and the stress/displacement distributions of its surface(i.e. wall) and core are analyzed. The analysis is used to identify critical locations where damage is prone to occur. Furthermore, cracking resistance of the microcapsule is determined for modified asphalt pavements. The results show that the contact pressure and contact tension of interior of asphalt mortar in asphalt concrete middle layer can be 0.347 N and 0.093 N respectively under 1.43 MPa tire pressure. The average contact pressure and contact tension are found to be 25 mN and 7.7 mN respectively among microcapsules. The FEM analysis on the single microcapsule show that bearing pressure region is the compression area of microcapsule. However, near the loading area, in the compression direction, the microcapsules bear significant tensile stresses. Moreover, the peak stresses appear near the edge of the load and it is where microcapsules likely develop cracks.