纳米叠层金属基复合材料(nano-laminated metal matrix composites,NLMMCs)由金属和增强材料(陶瓷、非晶以及纳米碳材料)以层状形式交替叠加组成,是构型化金属基复合材料的一种典型代表。由于组分相的纳米尺度、叠层构型以及大量的异质...纳米叠层金属基复合材料(nano-laminated metal matrix composites,NLMMCs)由金属和增强材料(陶瓷、非晶以及纳米碳材料)以层状形式交替叠加组成,是构型化金属基复合材料的一种典型代表。由于组分相的纳米尺度、叠层构型以及大量的异质界面,NLMMCs表现出优异的综合力学和功能性能,成为近年来材料科学的研究热点。以金属-陶瓷型、金属-非晶型和金属-纳米碳型NLMMCs为主要对象,重点综述了NLMMCs的常见制备工艺及相应的特点,并聚焦于采用微纳力学方法探究内在和外在特征尺度、叠层取向以及界面特性等对其强韧化和变形机制影响的研究新进展。最后展望了NLMMCs的发展趋势,指出了NLMMCs在特定服役条件下的力学响应机制有待进一步研究,提出了需要开发适用于在多物理场下工作的微纳尺度材料表征和测试系统,以便更精准地探究NLMMCs的使役行为。展开更多
The aim of the investigations presented here was to understand how the stiffness of the adhesive affects the failure of ceramic tiles adhered to metallic backings. The working hypothesis was that varying the adhesive ...The aim of the investigations presented here was to understand how the stiffness of the adhesive affects the failure of ceramic tiles adhered to metallic backings. The working hypothesis was that varying the adhesive stiffness could have the same effect on the ballistic performance as a variation of the adhesive thickness.Two different projectile/target combinations were utilized for ballistic tests in order to generate extremely different loading conditions. With targets consisting of 6 mm aluminum oxide ceramic and 6 mm aluminum backing, complete penetration occurred in each test with 7.62 mm tungsten carbide core AP ammunition at an impact velocity of 940 m/s. In contrast, with ceramic tiles of 20 mm thickness on 13 mm steel backing,no penetration of the ceramic occurred at the impact of a 7.62 mm ball round at 840 m/s.Four different types of adhesive(high-strength till high-flexible) were tested in both configurations. The elongation of the adhesive layer, the deformation of the metallic backing and the failure of the ceramics were observed by means of a high-speed camera during the projectile/target interaction.The results of the ballistic tests showed that a higher fracture strain caused a larger deformation of the backing compared to adhesives, which exhibit a high tensile strength and low fracture strains.The experimental results indicate that the damage behavior of the ceramic/metal composites depends on the absolute elongation of the adhesive layer. This can be controlled either by the thickness or the stiffness of the bonding layer.展开更多
文摘作为热结构材料,陶瓷基复合材料(ceramic matrix composites,CMC)在航空航天领域应用潜力巨大。连续纤维的引入解决了陶瓷脆性大的问题,而纤维与基体间微小区域——界面层的设计是保证CMC具有高韧性的关键。一直以来相关研究主要集中于界面层与CMC宏观力学性能之间的关系,受限于表征难以深入研究界面层微区力学行为的困难。随着微纳力学测试与聚焦离子束(focused ion beam,FIB)技术的发展,近些年来对于CMC界面层结合强度以及其失效行为的表征逐渐增多。在此基础上,本文综述CMC中界面层的作用以及界面剪切强度的影响因素与调控机制,同时汇总当下通过直接或间接手段测试界面剪切强度的方法,重点总结微纳力学手段下纤维push-out/push-in以及微柱压缩等方法的适用条件以及差异,报道这些方法在界面区失效机制研究方面的进展,并指明尚存在的一些问题。其中,纤维pushout/push-in可以反映基体应力作用对界面剪切强度的影响,但测试结果可能受到外部因素的影响;而微柱压缩测试则更多地反映界面层本征特性,无法反映基体应力对界面剪切强度的影响,也无法反映纤维拔出过程。最后展望未来的研究方向:进一步拓展界面微区力学行为的表征方法,同时确定微区力学与宏观力学性能间的影响机制并建立模型,最终实现CMC的界面层优化。
文摘纳米叠层金属基复合材料(nano-laminated metal matrix composites,NLMMCs)由金属和增强材料(陶瓷、非晶以及纳米碳材料)以层状形式交替叠加组成,是构型化金属基复合材料的一种典型代表。由于组分相的纳米尺度、叠层构型以及大量的异质界面,NLMMCs表现出优异的综合力学和功能性能,成为近年来材料科学的研究热点。以金属-陶瓷型、金属-非晶型和金属-纳米碳型NLMMCs为主要对象,重点综述了NLMMCs的常见制备工艺及相应的特点,并聚焦于采用微纳力学方法探究内在和外在特征尺度、叠层取向以及界面特性等对其强韧化和变形机制影响的研究新进展。最后展望了NLMMCs的发展趋势,指出了NLMMCs在特定服役条件下的力学响应机制有待进一步研究,提出了需要开发适用于在多物理场下工作的微纳尺度材料表征和测试系统,以便更精准地探究NLMMCs的使役行为。
文摘The aim of the investigations presented here was to understand how the stiffness of the adhesive affects the failure of ceramic tiles adhered to metallic backings. The working hypothesis was that varying the adhesive stiffness could have the same effect on the ballistic performance as a variation of the adhesive thickness.Two different projectile/target combinations were utilized for ballistic tests in order to generate extremely different loading conditions. With targets consisting of 6 mm aluminum oxide ceramic and 6 mm aluminum backing, complete penetration occurred in each test with 7.62 mm tungsten carbide core AP ammunition at an impact velocity of 940 m/s. In contrast, with ceramic tiles of 20 mm thickness on 13 mm steel backing,no penetration of the ceramic occurred at the impact of a 7.62 mm ball round at 840 m/s.Four different types of adhesive(high-strength till high-flexible) were tested in both configurations. The elongation of the adhesive layer, the deformation of the metallic backing and the failure of the ceramics were observed by means of a high-speed camera during the projectile/target interaction.The results of the ballistic tests showed that a higher fracture strain caused a larger deformation of the backing compared to adhesives, which exhibit a high tensile strength and low fracture strains.The experimental results indicate that the damage behavior of the ceramic/metal composites depends on the absolute elongation of the adhesive layer. This can be controlled either by the thickness or the stiffness of the bonding layer.
