Anisotropic strength and fracture resistance of epoxy-ceramic composite materials produced by ultrasound freeze-casting
Anisotropic strength and fracture resistance of epoxy-ceramic composite materials produced by ultrasound freeze-casting
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DOI：
10.1016/j.ceramint.2021.11.027
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发表时间：
2021-11
影响因子：
5.2
通讯作者：
C. Tanaka;M. Mroz;S. Naleway;J. Kruzic
中科院分区：
文献类型：
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作者：
C. Tanaka;M. Mroz;S. Naleway;J. Kruzic
超声冷冻铸造环氧陶瓷复合材料的各向异性力学性能进行了研究，通过测量弯曲强度和断裂阻力曲线（R曲线），使用无缺口和缺口三点梁弯曲实验，分别在三个不同的方向相对于定向冻结轴切割。使用0.699、1.39和2.097 MHz的三种超声频率，以便将不同的长度尺度引入到微结构中，其中0 MHz用作对照样品。对于所有的情况下，复合材料表现出较高的强度和断裂阻力时，裂纹平面切割的方向上的冰的生长（表示为YX方向）。各向异性性质对于在没有超声（0MHz）的情况下生产的材料更明显，其中与两个正交取向相比，YX取向的弯曲强度高约160%。发现大部分断裂阻力增加发生在裂纹延伸Δa ≤ 0.5 mm内。比较高度各向异性0 MHz样品在Δa= 0.5 mm处的抗断裂性表明，YX取向比两个正交取向韧性约86%。当施加0.699、1.39和2.097 MHz的超声操作频率时，强度和抗断裂性中的各向异性量随着操作频率的增加而逐渐减小。YX取向的高强度和抗断裂性归因于陶瓷颗粒沿着冻结前沿方向的排列，从而产生裂纹扩展的屏障。超声波改变材料的微观结构，引入相对致密的陶瓷层垂直于冻结前沿方向，作为一个额外的，正交的裂纹扩展的障碍。添加较致密的层起到改善较弱取向的机械性能并降低总体各向异性的作用。
The anisotropic mechanical properties of ultrasound freeze cast epoxy-ceramic composite materials were studied by measuring flexural strength and fracture resistance curves (R-curves) using both unnotched and notched three-point beam bending experiments, respectively, cut in three different orientations relative to the directional freezing axis. Three ultrasound frequencies of 0.699, 1.39 and 2.097 MHz were used in order to introduce different length scales into the microstructure, with 0 MHz used as the control samples. For all cases, the composites showed higher strength and fracture resistance when the crack plane cut across the direction of ice growth (denoted as the YX orientation). The anisotropic properties were more evident for the material produced without ultrasound (0 MHz) where the flexural strength was approximately 160% higher for the YX orientation compared to two orthogonal orientations. Most of the fracture resistance increase was found to occur within a crack extension, Δa, of ∼0.5 mm. Comparing the fracture resistance at Δa= 0.5 mm for the highly anisotropic 0 MHz samples showed that the YX orientation was approximately 86% tougher than the two orthogonal orientations. When the ultrasound operation frequencies of 0.699, 1.39 and 2.097 MHz were applied, the amount of anisotropy in the strength and fracture resistance gradually decreased as the operating frequency increased. The high strength and fracture resistance for the YX orientation was attributed to the alignment of the ceramic particles along the freeze front direction creating a barrier for crack propagation. Ultrasound modifies the material microstructure, introducing relatively dense ceramic layers perpendicular to the freezing front direction that act as an additional, orthogonal barrier to crack propagation. The addition of the denser layers acts to improve the mechanical properties in the weaker orientations and reduce the overall anisotropy.