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Delamination fatigue growth in polymer-matrix fibre composites: A methodology for determining the design and lifing allowables

机译：聚合物基纤维复合材料的分层疲劳增长：一种确定设计和起落许可的方法

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摘要

The introduction, originally in 2009, by the FAA of a 'slow growth' approach to the certification of polymer-matrix fibre composites has focused attention on the experimental data and the analytical tools needed to assess the growth of delaminations under cyclic-fatigue loads. Of direct relevance is the fact that fatigue tests on aircraft composite components and structures reveal that no, or only little, retardation of the fatigue crack growth (FCG) rate occurs as delamination/ impact damage grows. Therefore, of course, the FCG data that are ascertained in laboratory tests, and then employed as a material-allowable property to design and life the structure, as well as for the development, characterisation and comparison of composite materials, must also exhibit no, or only minimal, retardation. Now, in laboratory tests the double-cantilever beam (DCB) test, using a typical carbon-fibre reinforced-plastic (CFRP) aerospace composite, is usually employed to obtain fracture-mechanics data under cyclic-fatigue Mode I loading. However, it is extremely difficult to perform such DCB fatigue tests without extensive fibre-bridging developing across the crack faces. This fibre-bridging leads to significant retardation of the FCG rate. Such fibre-bridging, and hence retardation of the FCG, is seen to arise even for the smallest values of the pre-crack extension length, a(p)-a(0), that are typically employed. The results from the DCB tests also invariably exhibit a relatively large degree of inherent scatter. Thus, a methodology is proposed for predicting an 'upper-bound' FCG curve from the laboratory test data which is representative of a composite laminate exhibiting no, or only very little, retardation of the FCG rate under fatigue loading and which takes into account the inherent scatter. To achieve this we have employed a novel methodology, based on using a variant of the Hartman-Schijve equation, to access this 'upper-bound' FCG rate curve, which may be thought of as a material- allowable property and which is obtained using an 'A basis' statistical approach. Therefore, a conservative 'upper-bound' FCG curve may now be calculated from the DCB laboratory test data for material development, characterisation and comparative studies, and for design and lifing studies.
机译：由美国联邦航空局（FAA）最初于2009年推出的一种“缓慢增长”的方法来认证聚合物基纤维复合材料，将注意力集中在了评估循环疲劳载荷下分层增长所需的实验数据和分析工具上。直接相关的事实是，对飞机复合材料部件和结构的疲劳测试表明，随着分层/冲击损伤的增加，疲劳裂纹扩展（FCG）速率不会或只有很少的延迟。因此，当然，在实验室测试中确定的FCG数据，然后用作材料允许的属性来设计和使用结构，以及用于开发，表征和比较复合材料，也必须不显示，或只有极少的延迟。现在，在实验室测试中，通常采用典型的碳纤维增强塑料（CFRP）航空复合材料进行双悬臂梁（DCB）测试，以获取I型循环疲劳下的断裂力学数据。但是，要使这种DCB疲劳试验极其困难，而又不能在裂纹面上形成大量的纤维桥。这种纤维桥接导致FCG速率的显着降低。即使对于通常使用的裂纹前延伸长度a（p）-a（0）的最小值，也可以看到这种纤维桥接以及由此引起的FCG延迟。 DCB测试的结果也始终显示出较大程度的固有散射。因此，提出了一种用于从实验室测试数据预测“上限” FCG曲线的方法，该方法代表了复合层压板在疲劳载荷下没有或仅有很少的FCG速率延迟，并且考虑了固有的分散性。为了实现这一点，我们采用了一种新颖的方法，基于使用Hartman-Schijve方程的变体，来访问该“上限” FCG速率曲线，该曲线可以被认为是材料允许的特性，可以通过使用一种“基础”统计方法。因此，现在可以从DCB实验室测试数据中计算出保守的“上限” FCG曲线，以用于材料开发，表征和比较研究以及设计和寿命研究。

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  • 来源
    《Composite Structures》 |2018年第7期|8-20|共13页
  • 作者

    Yao Liaojun; Alderliesten R. C.; Jones R.; Kinloch A. J.;

  • 作者单位

    Delft Univ Technol, Struct Integr & Composites Grp, Fac Aerosp Engn, Delft, Netherlands;

    Delft Univ Technol, Struct Integr & Composites Grp, Fac Aerosp Engn, Delft, Netherlands;

    Monash Univ, Dept Mech & Aerosp Engn, Ctr Expertise Struct Mech, Clayton, Vic 3800, Australia;

    Imperial Coll London, Dept Mech Engn, Exhibit Rd, London SW7 2AZ, England;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Composites; Fatigue; Fracture mechanics; Delamination growth;

    机译：复合材料;疲劳;断裂力学;分层增长;

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