Theoretical and Experimental Studies of Failure in Anisotropic Curved Layered Structure

这项工作的主要目标是建立雄心勃勃的分析和实验计划，以了解和预测弯曲层状复合材料的破坏机理和机制。分析研究将针对：(A)确定在一般载荷下无裂纹弯曲复合材料的应力响应的弹性解析解，(B)预测初始失效模式(基体裂纹界面)，在特定临界载荷下基于适当的失效准则的失效位置，(C)确定不同柱面正交或各向异性介质之间的弯曲界面裂纹的应力奇异性和冲击弯曲界面的基质裂纹的应力奇异性。然后，有限元研究将侧重于：(A)开发奇异有限元来研究实际尺寸的试件对应于每种失效模式的裂纹尖端附近的应力场。该单元公式将包括从分析研究中获得的适当奇异项，(B)调查弯曲复合材料破坏过程的基本特征，重点是壳曲率的作用，(C)根据各种几何参数和载荷条件确定混合型断裂参数K1，K11和K111，(B)预测断裂模型和稳定性，不稳定的裂纹扩展或裂纹止裂。作为拟议工作的一部分，还将使用实验数据来制定和验证失效标准。将对分析预测、有限元结果和实验数据进行整理和批判性比较，以充分了解弯曲复合材料的失效行为和各种模型的预测能力。

The primary objective of this work is to establish and ambitious analytical and experimental program to understand and then to predict the failure mechanics and mechanisms of curved layered composites. Analytical studies will be directed towards (a) determining analytical elasticity solutions for the stress response of uncracked curved composites under general loadings, (b) predicting initial failure modes (interface of matrix cracking), failure locations based on proper failure criteria under specific critical loads, (c) determining stress singularities of curved interface crack between dissimilar cylindrically orthotopic or anisotropic media and of matrix cracking impinging on the curved interface. Finite element studies will then emphasize on (a) developing singular finite elements to investigate the stress fields near the crack tip corresponding to each failure mode for test specimens of practical dimensions. The element formulation will incorporate proper singular terms obtained from analytical study, (b) investigating the essential features of failure process in curved composites with emphasis on the role of shell curvature, (c) determining the mixed-mode fracture parameters K1, K11, and K111 in terms of various geometry parameters and loading conditions, (b) predicting fracture models and stable, unstable crack growth or crack arrest. Experimental data will be also used to develop and validate failure criteria as part of the proposed work. The analytical predictions, finite element results and experimental data will be collated and critically compared to provide a full understanding of both the failure behavior of curved composites and the predictive capability of various models.*** //