Frequency Effects on a Stiffness-Based Fatigue Failure Criterion in Flawed Composite Specimens
Frequency Effects on a Stiffness-Based Fatigue Failure Criterion in Flawed Composite Specimens
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DOI：
10.1520/stp27977s
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发表时间：
1977
期刊：
影响因子：
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通讯作者：
K. Reifsnider;W. W. Stinchcomb-W.;T. O'Brien
中科院分区：
文献类型：
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作者：
K. Reifsnider;W. W. Stinchcomb-W.;T. O'Brien
复合材料疲劳响应研究的一个重要结果是确定和表征了循环载荷（或应变）频率的影响。频率对带中心孔的硼/环氧和硼/铝板试件的疲劳响应有显著影响。早先已经报道了在不同频率下硼/环氧树脂和硼/铝的应变控制测试的大型数据库。最近，我们已经扩展了数据库，包括硼/环氧树脂和硼/铝使用刚度变化作为主要损伤参数的载荷控制试验结果，和允许的刚度变化作为故障标准。一般来说，数据表明，低频疲劳载荷产生更多的集中，局部，孔相关的损伤与相应的更大的试样刚度降低。相比之下，高频加载产生更多的轴向微结构相关的损伤和刚度降低较少的分散损伤。由于这些结果适用于两种差异很大的材料和不同的测试条件，因此作者认为这些效应代表了该现象的力学特性，而不是孤立的效应。看来，频率的影响，可以预期在许多纤维复合材料，他们是足够大，在许多工程应用中的重要后果。
An important result of our investigations of the fatigue response of composite materials has been the identification and characterization of the effect of frequency of cycled loads (or strain). Frequency has been found tosignificantly influence the fatigue response of boron/epoxy and boron/aluminum plate specimens with a center hole. A large data base for strain-controlled testing of boron/epoxy and boron/aluminum at different frequencies has been reported earlier. More recently, we have extended the data base to include load-controlled test results for boron/epoxy and boron/aluminum using stiffness change as the primary damage parameter, and allowable stiffness change as a failure criterion. In general, the data show that low-frequency fatigue loading produces more concentrated, local, hole-related damage with corresponding greater specimen stiffness reduction. In contrast, high-frequency loading produces more dispersed damage with more axial micro-structure-related damage and less stiffness reduction. Since these results are true for two widely different-materials and different testing conditions, the authors believe that these effects are representative of the mechanics of the phenomenon, and do not represent isolated effects. It appears that frequency effects can be expected in many fiberous composites and that they are large enough to be of significant consequence in many engineering applications.