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Relationship between the fracture toughness of bulk polymer and fiber-reinforced polymer composites.

机译：本体聚合物和纤维增强聚合物复合材料的断裂韧性之间的关系。

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摘要

Improving the fracture toughness of the polymer matrix has been a concentration of research effort for several years. However, improving the toughness of polymers is not sufficient to translate it into a greater toughness of their composites, because there is no linear relationship between the fracture toughness of polymer matrix and that of the composites. Failures in fiber-reinforced polymer (FRP) composites are often found to occur in the polymer matrix. This matrix-dominated fracture of FRP composites is controlled by the mechanics of crack growth in the matrix. Therefore, it is of great interest to establish a relationship between the fracture toughness of the bulk polymer matrix and the FRP composites. The presence of fibers affects the near tip stress field and governs the instability of the crack. The constraining due to fiber changes the K-dominance at the vicinity of the crack tip. In the present work, a brittle polymer was considered for a series of fracture experiments to study the effect of K-dominance. The critical stress intensity factor was found to be a function of the loading and specimen configurations. Therefore, the common notion of assuming that only critical stress intensity factor is necessary to predict the fracture behavior of brittle materials is questionable. Loading or specimen configurations changes the level of K-dominance. A detailed K-dominance zone analysis shows that singular stress field is not dominant for most cases, and consequently, the stress intensity factor alone cannot explain the fracture behavior. A two-parameter model, based on the both singular and nonsingular stress fields, was proposed and validated with the experiments. Further experiments were performed on the bulk polymer matrix and layered specimens of composites and polymer matrix. A two-parameter fracture model was proposed for the bulk polymer matrix, which follows the same trend as the FRP composites analyzed using layered local model. The adequacy of the conventional approach of calculating strain energy release rate was examined for the local model of composites based on the K-dominance zone size. Finally, a simplified fracture model was proposed for the FRP composites homogenized as an orthotropic solid. The predicted fracture load using the proposed fracture model for composites shows a good agreement with the experiment.
机译：多年来，提高聚合物基质的断裂韧性一直是研究的重点。然而，提高聚合物的韧性不足以将其转化为它们的复合材料的更大的韧性，因为聚合物基体的断裂韧性与复合材料的断裂韧性之间没有线性关系。通常会在聚合物基质中发现纤维增强聚合物（FRP）复合材料的失效。 FRP复合材料的这种基体为主的断裂是由基体中裂纹扩展的力学控制的。因此，建立本体聚合物基体和FRP复合材料的断裂韧性之间的关系非常重要。纤维的存在会影响尖端应力场，并控制裂纹的不稳定性。纤维引起的约束改变了裂纹尖端附近的K支配力。在目前的工作中，考虑将脆性聚合物用于一系列断裂实验，以研究K支配效应。发现临界应力强度因子是载荷和样品构型的函数。因此，假设仅临界应力强度因子才是预测脆性材料断裂行为的普遍观念是可疑的。加载或样本配置会更改K主导水平。详细的K主导区分析表明，在大多数情况下，奇异应力场并不占主导地位，因此，仅应力强度因子不能解释断裂行为。提出了基于奇异应力场和非奇异应力场的两参数模型，并通过实验进行了验证。在本体聚合物基体以及复合材料和聚合物基体的分层样品上进行了进一步的实验。提出了用于本体聚合物基体的两参数断裂模型，该模型遵循与使用分层局部模型分析的FRP复合材料相同的趋势。基于K支配区的大小，对复合材料的局部模型检查了计算应变能释放速率的传统方法的适当性。最后，针对均质为正交各向异性固体的FRP复合材料提出了简化的断裂模型。使用建议的复合材料断裂模型预测断裂载荷与实验结果吻合良好。

著录项

  • 作者

    Kumar, Bhawesh.;

  • 作者单位

    Purdue University.;

  • 授予单位 Purdue University.;
  • 学科 Engineering Aerospace.;Engineering Materials Science.;Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 114 p.
  • 总页数 114
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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