复杂曲面纤维-稀土镁合金超混杂层板蠕变时效成形机理研究

Super Hybrid Laminate (SHL) is a kind of hybrid composite which is cured by aluminum alloy and fiber layer alternately. It can be used to replace the aluminum alloy leading edge and the other key parts of aircraft, which can improve their anti-bird impact performance and fatigue life, and reduce the weight of 25-30%. However, formation of SHL with complex curved surface is easy to induce stress concentration between the interface of aluminum alloy and composite, which leads to delamination and fiber fracture failure, and limits its application in parts with complex curved surface. A new type of fiber/magnesium-rare earth alloy SHL is possible to be developed by substituting magnesium-rare earth alloy for aluminum alloy for its excellent specific strength and aging strengthening features. The creep age forming is suggested to form complex surface SHL to eliminate delamination and fiber fracture failure, which is based on the curing temperature range (140-200℃) of the resin and creep aging temperature range (160-250℃) of magnesium-rare earth alloy overlap each other, and the creep age forming can effectively reduce the stress concentration in parts. The main research contents in this proposal including, study on creep aging characteristics of magnesium-rare earth alloy, optimizing process parameters of SHL, setting up mechanical properties database, study on creep age forming mechanism of SHL. The implementation of this project will provide a theoretical basis and technical support for the wide application of SHL in the aircraft.

超混杂层板(Super Hybrid Laminates,SHL)是由铝合金与纤维预浸料交替铺层固化而成的层间混杂复合材料，用其替代飞机铝合金前缘等关键部位,可提高其防鸟撞性能和疲劳寿命，减重25-30%。但成形复杂曲面SHL易在铝合金和复合材料界面产生应力集中而导致分层和纤维断裂失效，限制其在复杂零件上应用。基于稀土镁合金具有优异的比强度和时效强化特性，本项目拟采用其替代SHL中铝合金以开发新型纤维-稀土镁合金SHL，利用纤维预浸料固化温度区间(140-200℃)和稀土镁合金蠕变时效温度区间(160-250℃)互有重叠，及蠕变时效成形能有效降低零件应力集中，突破性运用蠕变时效成形方法成形复杂曲面SHL以避免分层和纤维断裂失效。研究内容包括：稀土镁合金蠕变时效行为研究；SHL热压复合及蠕变时效成形机理研究；建立SHL基础性能数据库。项目实施将为SHL在飞机的广泛应用提供理论基础和技术支撑。

纤维金属层板（Fiber metal laminates，FMLs），因其优越的抗损伤容限性能受到航天航空领域的关注。由于国外对FMLs制备和成形技术实行技术封锁，开发新型FMLs可以满足国内大型飞机快速发展对轻质高性能航空材料的迫切需求。本项目采用稀土镁合金替代FMLs中铝合金开发出新型NMFMLs并突破性运用蠕变时效成形方法成形复杂曲面NMFMLs以避免分层和纤维断裂失效。项目主要研究结果包括：基于统一理论，长大动力学及析出相强化理论，构建了稀土镁合金跨尺度蠕变时效本构方程，其蠕变应变量预测值误差为4.35%。系统研究了磷酸化、阳极氧化、微弧氧化与砂纸打磨的前处理方法对稀土镁合金粘接性能影响，研究结果表明：表面粗糙度对稀土镁合金的浸润性有显著的影响。磷酸化处理的稀土镁合金表面粗糙度及表面能最大，表面粗糙度Ra=4.17，表面能为70.8 mJ/m2。磷酸化、阳极氧化及微弧氧化处理后的界面粘接强度相比采用砂纸打磨处理可获得的增幅高达46%、61%及116%。微弧氧化工艺获得的界面粘接强度最高，其原因可以归结于微弧氧化产生的圆柱形孔更有利于热压固化过程中环氧树脂的浸入稀土镁合金表面，使得镁合金薄板与环氧树脂预浸料之间有更好的附着力。基于热压复合优化工艺的基础上开发出NMFMLs，该层板密度为1.69 g/cm3，相较于Glare层板的密度2.52 g/cm3，密度降低了大约33%，实现了更轻质层板的减重期望。在此基础上以典型的3/2结构层板研究对象，分别对单向和正交NMFMLs的弯曲性能、层间剪切性能及疲劳性能进行测试，并对其失效机理进行了分析，建立了NMFMLs基础性能数据库。在对层板弯曲失效分析时，考虑到稀土镁合金与纤维层以及纤维层与纤维层之间界面的失效形式，分别对稀土镁合金层、界面层及纤维复合材料层采用延性损伤准则、内聚力模型和Hashin失效准则，建立NMFMLs模型分析层板在弯曲加载过程中的渐进损伤行为。最后运用蠕变时效成形方法成形出C919飞机前缘典型部段，为NMFMLs在我过民机的应用提供数据支撑和技术支持。