The existence of weakly bonded areas will greatly affect the reliability of adhesively bonded structures in composite plates which are widely used in engineering applications. The timely and effective inspection of the adhesively bonded structure is crucial. In this paper, a simulation method of bonded quality based cohesive zone model(CZM) and the RAPID imaging method based ultrasonic guided wave detection technology are proposed to realize the detection and imaging of weakly bonded areas of adhesively bonded structures in composite plates. The CZM is innovatively used for the simulation of different bonded quality, it is achieved by modifying the constitutive relation curve of bilinear traction-separation law. Then, the influence of the degradation of bonded quality on the propagation characteristics of guided waves was explored. The results show that different bonded conditions have a significant impact on the guided wave propagation characteristics which enable the inspection of weakly bonded areas. Finally, based on the guided wave detection method and the cross covariance-based RAPID imaging algorithm, the detection and imaging of the weakly bonded area of the adhesively bonded structures are realized.
ABTRACT: Applications of Fiber-Reinforced Polymer (FRP) in Partially Confined Concrete: Improving Economic Value and Load-Bearing Capacity. However, there is still a need for more thorough analysis of the non-uniform vertical strain response and precise stress-strain models for FRP partially confined concrete. In this study, we used Digital Image Correlation (DIC) and strain gauges to collect data during axial compression tests on FRP partially confined concrete specimens. Additionally, partial confinement concrete is modeled using Finite Element Analysis using ABAQUS with a range of constraint area ratios, including 0, 1/4, 1/3, 1/2, 2/3, 3/4, and 1. According to the experimental findings, the specimens either responded to strain by hardening or softening in both the vertical and horizontal directions. For various constraint area ratios, the Finite Element results accurately reflected the relationship between surface constraint forces and axial strains in the x, y, and z axes. Under different constraint area ratios, a proposed stress-strain model showed high predictive accuracy for FRP partially confined concrete columns.
机翼翼梁是飞机的主承力构件,为了保证其成型质量和生产效率,需要采用自动化成型方式进行翼梁构件的生产制造.本文对目前翼梁成型方法的应用及研究现状进行了介绍,根据大尺寸变截面翼梁(长度大于10 m)的结构特点,研究了复合材料翼梁的自动铺丝成型技术.以M.TORRES龙门铺丝机为铺放平台,提出了翼梁的自动铺丝成型要点,确定了各个角度铺层的轨迹规划方法,结合轨迹规划情况,给出了翼梁的铺丝成型轨迹完善处理方案.最后,通过大尺寸复合材料翼梁的自动铺丝成型制造,验证了轨迹规划方法和轨迹处理方案的可行性与正确性,为国内自动铺丝技术在大尺寸复合材料翼梁成型上的应用提供参考.
碳纤维复合材料固化变形引起复合材料制件装配困难、残余应力等问题.因此,非常有必要建立复合材料构件制造过程引起变形缺陷的准确预报方法.本文对半经验模型与CHILE模型这两种应用最为广泛的固化变形仿真分析方法进行对比,并通过热压罐成型工艺试验对其进行验证.试验结果表明,这两种模型均可准确地模拟复合材料层合板的固化变形行为,其模拟误差均小于10％.基于CHILE模型研究材料参数对固化变形的影响,发现对固化变形影响最大的是玻璃态横向热膨胀系数,其次是橡胶态横向化学收缩系数.
为有效降低水平尾翼的重量,合理布置铺层方式,提高复合材料的利用效率,以某型复合材料水平尾翼为研究对象,借助专业分析软件Patran&Nastran建立了水平尾翼的有限元模型,校核了水平尾翼的静强度.设计制造了水平尾翼主承力结构试验件和试验夹具,并完成试验验证,试验结果表明二者应力分布基本一致,说明有限元模型是合理的.水平尾翼承受最大过载时,主承力件后梁最大应力远远小于材料许用值,以铺层厚度为设计变量,材料应力极限为约束对后梁铺层进行优化设计.结果表明:优化后的结构重量减轻了15.75％,且强度性能满足要求.
