ABSTRACT

The extensive aeronautic application of structural bonding motivated the development of numerous analytical models over the past century. Most of these models consider the adhesive to be uniform and in pristine conditions. Real-life bonded joints often contain localized manufacturing defects – e.g., porosity, partial cure – and degradation under environmental conditions – e.g., humidity, temperature. These deviations can reduce joints’ residual strength, contributing to premature failure in-service. This work proposes and evaluates two efficient continuum-mechanics-based closed-form methods for the stress analysis of complex bonded joints made of composite adherends and ductile adhesives in non-pristine conditions and subjected to general loading conditions. These models were based on a model for linear elastic functionally graded adhesives, which was generalized to incorporate adhesive plasticity using a linear equivalent modulus method and a non-linear deformation theory. The results indicate conservative residual strengths and strain distributions, agreeing with an existing analytical model for degraded joints and a detailed finite element model. Both proposed models demonstrated suitability for damage tolerance analyses and forensic investigations of real-life joints and repairs. The computational efficiency and robustness of the linear model are particularly applicable for sensitivity analyses and automated processes.

摘要

在过去的一个世纪中，结构粘合的广泛航空应用推动了众多分析模型的发展。这些模型中的大多数认为粘合剂是均匀的并且处于原始状态。现实生活中的粘合接头通常包含局部制造缺陷——例如孔隙率、部分固化——以及在环境条件下（例如湿度、温度）下的退化。这些偏差会降低接头的剩余强度，导致使用中过早失效。这项工作提出并评估了两种有效的基于连续体力学的封闭形式方法，用于在非原始条件下并承受一般载荷条件下对由复合粘附体和延性粘合剂制成的复杂粘合接头进行应力分析。这些模型基于线性弹性功能梯度粘合剂模型，它被推广到使用线性等效模量方法和非线性变形理论结合粘合剂塑性。结果表明保守的残余强度和应变分布，与现有的退化接头分析模型和详细的有限元模型一致。两种提议的模型都证明了适用于损伤容限分析和真实接头和修复的法医调查。线性模型的计算效率和稳健性特别适用于敏感性分析和自动化过程。同意现有的退化接头分析模型和详细的有限元模型。两种提议的模型都证明了适用于损伤容限分析和真实接头和修复的法医调查。线性模型的计算效率和稳健性特别适用于敏感性分析和自动化过程。同意现有的退化接头分析模型和详细的有限元模型。两种提议的模型都证明了适用于损伤容限分析和真实接头和修复的法医调查。线性模型的计算效率和稳健性特别适用于敏感性分析和自动化过程。