Numeriacal Simulation For Interlaminar Stress Of Laminated Composite Under Uniform Axial Deformation And The Elevated Temperature Creep Of 40Cr Steel

This paper includes two parts. The first part is the analysis of interlaminar stress of laminated composite plates under uniform axial deformation. The second part is the constitutive equation of elevated temperature creep of 40Cr steel.The strength of the laminated composite is smaller than the single-layer composite. One important reason of this phenomenon is the interlaminar stress at the interface. Therefore, the research on the interlaminar stress is very important in the practical application.The first shear deformation theory is superimposed on the layerwise theory as to analyze the interlaminar stress. First, the displacement is substituted into the strain-displacement relationship and the stress-strain relationship. Then the result is substitute into the principle of virtual work to derive the governing equations. Second, the finite element equation is derived according to the principle of virtual displacement. Then the displacement field is simplified for the composite laminated plates subjected to a uniform axial strain.A 3-node linear Lagrange element is employed to analyze the interlaminar stress. Besides, the accuracy of the stress is ensured as it is an exact value at the Gauss point of the element. Furthermore, this paper puts emphasis on the composite laminated plates subjected to a uniform axial strain, and its interlaminar stress is analyzed on the following aspects:1) The stress along y-axis and z-axis is analyzed for different composite laminated plates. The interlaminar stress(σ_z,σ_xz andσ_yz)in the vicinity of the edge is much higher than at the area far from the edge, and it changes sharply in the vicinity of the edge, such as increase or decrease sharply or a peak is happened in this area. And the stress along z-axis in the vicinity of the edge is very different from the area far from the edge. The interlaminar stress would like to change sharply at the interface. The sign of stressσ_yz changes suddenly at the interface±θ.2) The influence of layer number on the interlaminar stress is investigated for the cross ply composite laminated plates. It is found that stressσ_xz doesn't change with the layer number and its value is always zero. When the plate is symmetric, the curve of stressσ_z is symmetric about the middle surface of the plate and the curve of stressσ_yz is antisymmetric about the middle surface. Besides, the value of stressσ_z is changed with the layer number while the variation of the stress at the initerface is similar. At the interface, a sharp peak is happened in the curve of stressσ_yz whatever the layer number is changed or not. Moreover, the value of this peak doesn't affected by the layer number.3) The influence of the ply angle on the interlaminar stress is investigated for the composite laminated plates [θ/-θ]s. The value of the interlaminar stress is changed with the angle while the shape of the stress along z-axis is similar. Besides, the interlaminar stress becomes higher then smaller as the angle varied between 0 and 60°. And it is close to zero when the angle varied between 60°and 90°.The creep behaviors of the 40Cr steel are investigated at various temperatures and stresses in the second part of this paper. And the creep curves based on the experimental datas are plotted. It can be observed that the steady creep and the accelerating creep processes are the dominant parts of the creep curves of the 40Cr steel in the experimental conditions. Besides,the steady creep rates can be described by the Norton-Power law and the creep datas can be fitted by the Monkman-Grant relationship. Then, a nonlinear constitutive equation for the 40Cr steel is proposed according to the experimental datas. The parameters of the equation are determined by the least square method. At last, it can be found that the proposed equation can describe the creep behaviors of the 40Cr steel quite well by comparing the theoretical results which are calculated by the proposed equation and the experimental datas.