中间层厚度对三明治结构中I型断裂能量释放率的影响研究

EFFECT OF INTERLAYER THICKNESS ON THE MODE I FRACTURE ENERGY RELEASE RATE OF SANDWICH STRUCTURE

三明治结构作为载荷传递和连接元件,广泛应用于航空航天、材料表征、柔性电子等领域.了解其断裂行为和特点能为三明治结构连接件极限载荷的设计提供理论指导.基于改良弹性地基理论模型,本文提出了一种计算能量释放率的新理论模型,模型中考虑中间层厚度对三明治结构I型断裂能量释放率的影响.结果表明,中间层厚度对三明治结构I型断裂的影响存在两个部分:中间层剪切力的影响及中间层引起结构刚度增大的影响.当无量纲中间层厚度取最大值2时,传统模型与有限元计算结果存在70%以上的误差;采用本文的模型可以极大地提高精度,将误差降到5%以内.相比改良弹性地基理论只适用于中间层厚度较小的情况,本理论模型的适用范围更广.此外,利用本模型,本文选取了两个几何参数(中间层厚度和裂纹初始长度)和一个材料参数(模量比)进行研究.讨论了剪切效应对结构几何和材料参数的敏感性.在定载荷的基础上,讨论了几何和材料参数对能量释放率的影响;并在假定结构断裂韧性不变的基础上,得到了几何和材料参数对三明治结构临界载荷的影响规律.

As a load transfer and connection element, the sandwich structure is widely used in aerospace, material characterization, flexible electronics and other fields. Understanding its fracture behavior and characteristics can provide theoretical guidance for designing the load capacity of the sandwich structure connector. In this paper, based on the improved elastic foundation theoretical model, we proposed a new theoretical model to calculate the energy release rateof the sandwich structure. The theoretical model considered the effect of the interlayer thickness on the energy release rate of the mode I fracture energy of the sandwich structure. Results showed that the influence of the middle layer on the energy release rate of mode I fracture has two parts: the influence of the shear force of the middle layer and the effect of the middle layer on the increase of structural stiffness. When the dimensionless interlayer thickness takes the maximum value of 2, the energy release rate from the traditional model may have a deviation greater than 70%, compared with the finite element calculation;our model can greatly improve the accuracy, and the error can be reduced to 5%. Compared with the improved elastic foundation theory, which is only applicable to the case where the thickness of the middle layer is small,the theoretical model has a wider range of applications. In addition, by using the present model, two geometric parameters(intermediate layer thickness and initial crack length) and one material parameter(modulus ratio) were selected for the study. The sensitivity of shear effect to structural geometry and material parameters was discussed. Based on the constant load, the influence of geometric and material parameters on the energy release rate was discussed;and on the assumption that the fracture toughness of the structure remains unchanged, the influence law of geometric and material parameters on the critical load of the sandwich structure was obtained.