FRP 层压复合梁结构屈曲变形在线监测方法

为了实现梁结构屈曲变形在线监控，提出了一种FRP层合梁屈曲变形重构方法。首先，依据高阶剪切变形理论，提出了一种复合梁结构变形场描述方法，并基于冯卡门应变梯度理论，推导出了中性轴应变表述方式。然后，利用最小二乘变分法建立了位移重构模型。其中，利用四次B-样条基函数构造了屈曲变形位移插值函数，推导了理论中性轴应变计算公式。并基于少量应变测量，提出了非线性项应变解耦方法，建立了测量应变与实测中性轴应变转换关系。最后，为了验证所提方法的精确性，以25层碳纤维复合梁为样件，搭建固定-简支梁试验平台，对其进行数值计算和试验论证。结果表明，建立的屈曲变形重构模型在不同轴向载荷作用时，位移场重构误差均小于8%。

Online monitoring method for buckling deformation of FRP laminated beams

To achieve the online monitoring of the buckling deformation of the beam structure, a shape sensing method for monitoring the buckling deformation of FRP composite beam structure is proposed. Firstly, according to the higher order shear deformation theory, a method for describing the deformation field of laminate composite beam structure is proposed. Based on the von Karman strain gradient theory, the section strain expressions are derived. Then, the least square function is employed to formulate the displacement reconstruction model. In this model, the displacement interpolation functions are constructed by using the quartic non-uniform rational Bsplines (NURBS) basis function as the shape function, and the theoretical section strain field formulation is derived. Based on a small number of discrete point strain measurement values, a nonlinear strain decoupling method is proposed, and the transformation relationship between surface strains and measured section strains is established. Finally, to evaluate the accuracy and effectiveness of the proposed method, a simply supported beam test platform is established with 25 layer carbon fiber composite beams as samples, and its numerical calculation and experimental demonstration are carried out. Results show that the proposed model and the reconstruction displacement error is less than 8% under different axial loads.