Analysis Of Interlaminar Stress Of Laminated Composite Plate With Holes

Carbon fiber-reinforced laminated plate becomes a necessary kind of material in planes, satellites and rocket etc, for its high strength ratio, designability, stable structural scale, resistance to fatigue fracture and whole forming in large area. In engineering applications, there are some holes on composite laminates for connection or installation. However, the free-edges effect will commence delamination and weak the strength and stiffness, leading to the premature failure of the composite laminates. So, the interlaminar stress distribution near hole edge needs to be analyzed. Due to this need, it is crucial to research the numerical simulation method and analysis technology of an accurate evaluation of interlaminar stress near hole edge in composite laminates.Under these requirements, in this paper, a domestic carbon fiber composite laminate with a hole was analyzed by experiment and numerical simulation. This laminated plate was subjected to uniaxial forces and composed of layers with typical ply angles (0°/±45°/90°). Interlaminar stresses distributions near hole edge were investigated. A method was developed to predict the accurate interlaminar stresses near hole edge using three-dimensional finite element numerical simulation. The main researching contents were given as following.(1) Tensile experimental investigation of domestic carbon fiber-reinforced composite laminate with holes. Experiment of domestic carbon fiber-reinforced composite laminate under drawing forces was performed by electrical and optical measurement. Equivalent elastic modulus of the whole laminate was measured using the electrical measurement. By optical measurement, the change of the fields of displacement and strain near the hole was always measured during the whole process from the beginning until failure. According to the change of these fields, the load of the micro-structure breakage interlaminar stress-induced was observed simply.(2) Designing model technology for analyzing interlaminar stress based on the three-dimensional finite element. Meshes were refined in the domain close to the hole in order to obtain the interlaminar stress accurately. Theoretically, the analytical results are more accurate if the computational domain is closer to the original model and the meshes are denser. However, too large regional and too many meshes bring too much calculation quantity, and even exceed the ability of computer. The proper analysis domain and desity of meshes are important to obtain the numerical results within the calculating resources provided. Therefor firstly, the areas affected only by the hole were determined for ply angle 0°/±45°/90°respectively. The effects of the structure length on the interlaminar stress distribution were investigated when the structure width was certain. And also the critical length was obtained. Secondly, the meshing rules were determined for accurate and efficient simulation by discussing the meshing in three ways:through the thickness; along radial lines away from the hole; and around the hole. Last, the model was verified effectivly by comparing the numerical and experimental results.(3) Investigation of the interlaminar stress distribution rule near hole edge for domestic carbon fiber-reinforced composite laminate with a hole. The distribution of interlaminar stress near hole edge for the domestic carbon fiber-reinforced composite laminate was analyzed. A three-dimensional finite element model was performed and subjected to uniaxial forces. First, The effects of the ply parameters on the interlaminar stress distribution were investigated. The ply parameters include the location and the stacking sequence, such as angle 1/angle 2 or angle 2/angle 1.The trends of the effects of the ply parameters on the interlaminar stress distribution were obtained. Then, the stress distributions were analyzed in detail in four ways:around the hole; along radial lines away from the hole; through the thickness; and in different typical interfaces. In the meantime, the interfaces and locations occurring the maximum interlaminar stress were presented, which will provide the reference for the laminate design.This research was supported by the Major Program (10902019) of the National Nature Science Foundation of China. The financial supports are gratefully acknowledged.