超声波焊接热塑性复合材料波纹夹芯结构的工艺力学与失效机理研究

Owing to their high strength-to-weight ratio, light-weight thermoplastic composite sandwich structures with corrugated cores are increasingly attractive to aerospace and automotive industries. However, composite sandwich structures present a low interfacial strength between the face sheet and the core, which significantly limits the application of thermoplastic composites on light-weight structures. The current joining techniques, such as adhesive bonding and mechanical fastening, are not able to provide high-strength joints in thermoplastic composite structures. To tackle this problem, this project proposes a novel joining technology, namely ultrasonic welding, for the assembly of thermoplastic composite corrugated sandwich structures. A series of research, regarding of process simulation, welding experiments and static/dynamic mechanical characterization, is systematically carried out. First, a thermal-mechanical coupled model is developed about the interface of thermoplastic composite corrugated structures during the welding process, demonstrating the effects of welding and geometric parameters on thermal-mechanical behaviour of the interface. Subsequently, the methodologies of process mechanics and quality evaluation for ultrasonic welding of thermoplastic composite corrugated structures is proposed. The relationship between the welding process and mechanical behaviour of the structure is implied. Finally, quasi-static compressive and low-velocity impact tests are performed on the welded thermoplastic composite corrugated structures, to investigate their static/dynamic mechanical response and the failure mechanism. This research is aiming at gaining some innovative achievements on design, manufacturing and mechanical characterization of thermoplastic composite sandwich structures with corrugated cores, thus providing guidance for their engineering applications.

轻量化热塑性复合材料波纹夹芯结构由于质量轻、承载强等特点，受到航空、汽车等领域的广泛关注。然而，当前夹芯结构面板与芯层的界面强度较低，极大地限制了热塑性复合材料轻量化结构的应用。目前已有的面芯连接技术，如胶接、铆接等，难以在热塑性复合材料结构中形成高强度界面连接。针对这一问题，本项目创新性地提出采用超声波焊接技术连接热塑性复合材料波纹夹芯结构，开展过程模拟、结构制造以及静动态力学性能表征的系统性研究。建立热塑性复合材料波纹夹芯结构超声波焊接界面处的热-力耦合模型，阐明工艺参数与结构构型对界面热力学行为的影响；发展热塑性复合材料波纹结构超声波焊接的工艺力学及质量评价方法，揭示焊接工艺与结构强度之间的内在响应规律；开展面外压缩与落锤冲击实验表征焊接波纹结构的力学性能，并揭示结构的失效模式与破坏机理。研究期望在热塑性复合材料夹芯结构设计制造与力学性能表征方面获得原创性成果，为其工程应用提供指导。

热塑性复合材料（Thermoplastic composites, 简称TPC）波纹夹芯结构由于质量轻、承载能力强等特点，在航空航天等高端装备领域具备极为优异的应用潜力。然而，传统的机械连接或胶接技术无法为高性能热塑性复合材料波纹夹芯结构提供可靠的面芯连接强度，从而导致结构发生面芯脱粘而过早失效，严重限制了热塑性复合材料轻量化结构的应用。本课题提出了基于超声焊接技术的热塑性复合材料轻量化波纹结构的设计制造方法，发展了面向热塑性复合材料波纹结构焊接界面的力-热耦合模型，揭示了超声焊接过程中波纹面芯界面的熔融演化机理，并采用有限元技术提出了面向大型复合材料焊接结构的连接设计及优化方法；在此基础上，发展了面向大尺寸复合材料结构的超声焊接工艺力学方法，分析了不同焊头对工艺的影响机制，同时建立了基于微焦点CT技术的超声焊接工艺质量评价方法；基于轻量化复合材料波纹结构，开展了静动态力学试验，表征了波纹夹芯结构在静动态载荷条件（压缩、冲击、振动等）下的力学响应特性，揭示了结构的失效机理。.基于项目的支持，研究在《Composites Part B: Engineering》、《Composite Structures》、《Thin-walled Structures》、《航空学报》等期刊发表论文9篇，申请发表专利2项，参加国内外学术会议4次，并做学术报告。基于项目发展的复合材料结构设计与焊接制造技术已经拓展至航空航天构件，形成工艺规范，部分进入考核阶段。