Analytical models for stress analysis of real-life bonded joints

Abstract

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.