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为适应纤维经、纬向缠绕,本文研究由4个90°弯管组成的环。由于90°弯管中圆弧段应力比直管段大,因而取环壳为力学模型进行纤维缠绕玻璃钢弯管结构设计和强度计算。本文研究的玻璃钢环壳之纤维是弹性主方向、正交缠绕的。该壳的特点是正交异性、变厚度、无耦合效应。由线性弯曲理论推出了受内压P作用的缠绕玻璃钢环壳极限方程,它是含两个变量的二阶微分方程组。引入复变量后,得到一个二阶复变量微分方程,用三角级数解该方程,导出了内力、应力和变形计算式。比较了有矩理论和无矩理论解之后,指出:在工程实用中可用无矩理论近似求解,误差不大于5％。缠绕玻璃钢90°弯管采用复合结构。本文指出可用网络理论进行增强层结构设计。给出了经、纬向正交缠绕玻璃钢环壳平衡型设计时纤维用量比公式,还给出了强度计算式,最小壁厚h_0、额定工作压力P_B的设计计算式。本文介绍了实验方法,用实验验证了上述公式的正确性,为缠绕玻璃钢90°弯管设计提供了理论依据。本文还分析了受内压P作用时截面是椭圆的环壳,给出了长、短轴在对称轴上的内力和应力计算式。
In order to adapt to fiber warp and weft entanglement, we study a loop composed of four 90 ° elbows. Because the circular arc section stress in 90 ° elbow is larger than that in straight pipe section, the ring shell is taken as the mechanical model to design the fiberglass elbow structure and the strength calculation. The fiber of FRP ring shell studied in this paper is the main direction of elasticity, orthogonal winding. The shell is characterized by orthotropic, variable thickness, and no coupling effects. According to the theory of linear bending, the limit equation of the annular FRP ring wrapped by internal pressure P is derived. It is a second-order differential system with two variables. After the complex variable is introduced, a second-order complex variable differential equation is obtained, and the equations of internal force, stress and deformation are deduced by triangular series solution. After comparing the moment theory with the momentless theory, it is pointed out that the approximate solution of the momentless theory can be used in the engineering practice with the error less than 5%. Winding glass fiber reinforced plastic 90 ° elbow composite structure. This paper points out the network structure can be used to enhance the design. The formula of fiber amount ratio in balanced design of FRP ring and shell in orthogonal weft and zonal direction is given, and the formula for calculating the strength formula, the minimum wall thickness h_0 and the rated working pressure P_B is also given. In this paper, the experimental method is introduced. The correctness of the above formula is validated by experiments, which provides a theoretical basis for the design of 90 ° bend pipe wrapped around glass fiber reinforced plastic. In this paper, we also analyze the ring shell with elliptical cross section under the action of internal pressure P, and give the formulas for calculating the internal forces and stresses on the symmetrical axes of the long and short axes.