复合材料胶接质量的非线性孤波表征及检测方法研究

Bonding of composite through adhesives is a practical joint method for joining composite parts to cured composite plate, sandwich components or metal plates. The bonded composite structures, such as laminated composite plates, adhesive joints and honeymoon sandwich, are attractive for aerospace and automotive structural applications. The nondestructive testing to such bonded composite structures is a challenging problem in this area that needs to be addressed. A novel high-resolution method based on nonlinear solitary wave is proposed in this project to non-destructively detect the embedded defects or weak bonding interfaces. The research topics include: (1) Investigate the propagation characteristics of the nonlinear solitary wave in a one-dimension granular chain in consideration of plasticity and viscoelasticity of granule materials. Furthermore, develop an optimal method for granular chain design to improve the excitation energy of solitary wave and adjust its propagation characteristics. (2) Establish a numerical model for revealing the property of dynamic contact between solitary wave and the bonded composite structures which have support boundary and weak bonding interfaces. Then, the sensitivity matrix of solitary wave to the quality of bonded composite structures can be obtained. (3) A tunable transduction system for exciting and receiving chains of solitary waves will be developed, in which the preload and impact condition can be adjusted for various defect detection applications. The defect sizes and location or the level of the weak bonding can be quantitatively assessed. The research outcomes of this project can provide powerful technical supports for manufacturing quality control and in-service testing for composite bonding structures.

利用胶黏剂将已固化的复合材料制件与其它已固化复合材料制件、夹芯或金属件进行胶接连接，称作复合材料胶接。复合材料胶接结构（层压板、接头和蜂窝夹层等）在航空航天、汽车制造中应用广泛，其胶接质量的无损检测是该领域内亟待解决的技术难题。本项目提出一种非线性孤波检测新方法，实现对复合材料胶接结构缺陷、弱胶接界面的高灵敏度、无损定征。主要研究内容包括：(1) 考虑材料塑性、粘弹性，研究一维颗粒链中非线性孤波传播特性，发展可提高孤波激发能力，调控孤波传播特性的一维颗粒链优化设计方法；（2）建立考虑边界条件、弱胶接界面的孤波与胶接结构动态接触模型，分析得出孤波信号特征参量对胶接质量变化的灵敏度矩阵；（3）研制预压力、冲击条件等可调控的孤波探测传感装置，激励孤波、孤波串对复合材料胶接结构进行检测，实现缺陷大小、深度及弱胶接程度的定量评估。通过上述研究，为复合材料胶接结构制造质量控制和在役检测提供技术支撑。

本项目在一维颗粒链中非线性孤立波（串）的形成机理揭示、传播特性分析与调控等科学问题上有突破和新进展。依据理论研究成果，发展了适用于无损检测的非线性孤立波（串）检测方法、装置，并开展了扎实的实验应用研究，很好地验证了新方法在金属/金属胶接结构、金属/复合材料胶接结构和钢筋混凝土结构无损检测应用的可行性和有效性。取得的主要成果如下：.（1）揭示了一维颗粒链中非线性孤立波串的形成机理，提出了3种孤立波串的形成方法。一维颗粒链中非线性孤立波串的形成主要原因是冲击颗粒与颗粒链的多次碰撞以及界面导致的应力波分解。利用入射孤立波在重-轻颗粒界面的波形分离特性，提出了基于复合颗粒球链的非线性孤立波串激励新方法。.（2）揭示了三段式“重-轻-重”复合颗粒链能量缓释现象的关键控制因素，提出了输出孤立波特性的调控方法。决定能量缓释特征的关键性参数为特征值λ=(ρv/ρs)• (Ev/Es)2/3，输出孤立波的声时随特征值λ变化呈现明显的两阶段规律。通过合理选择轻质颗粒材料的属性参数及数量，可以对“重-轻-重”复合颗粒链的输出孤立波特性进行有效调控。.（3）研制了高稳定性的非线性孤立波观察单元和多类型传感器，实现了金属/金属、金属/复合材料胶接结构中缺陷的无损检测，金属/复合材料胶接固化过程的监测，以及混凝土结构中预埋钢筋位置及深度的有效检测。