Defects and uncertainties of adhesively bonded composite joints

Abstract

The increasing use of fibre reinforced polymer composite materials in a wide range of applications increases the use of similar and dissimilar joints. Traditional joining methods such as welding, mechanical fastening and riveting are challenging in composites due to their material properties, heterogeneous nature, and layup configuration. Adhesive bonding allows flexibility in materials selection and offers improved production efficiency from product design and manufacture to final assembly, enabling cost reduction. However, the performance of adhesively bonded composite structures cannot be fully verified by inspection and testing due to the unforeseen nature of defects and manufacturing uncertainties presented in this joining method. These uncertainties can manifest as kissing bonds, porosity and voids in the adhesive. As a result, the use of adhesively bonded joints is often constrained by conservative certification requirements, limiting the potential of composite materials in weight reduction, cost-saving, and performance. There is a need to identify these uncertainties and understand their effect when designing these adhesively bonded joints. This article aims to report and categorise these uncertainties, offering the reader a reliable and inclusive source to conduct further research, such as the development of probabilistic reliability-based design optimisation, sensitivity analysis, defect detection methods and process development.

Synthesis and Mechanical Performances of Polyurethane Bio-Based Adhesives Resulted from the Depolymerization of Lignocellulose Biomass

“…Usually, the adhesive bonding is analyzed after the displacement of the bonded structures to study the propagation of the rupture upon applied stress at the macroscopic level. According to literature data, there are three possible types of adhesive bond failure that can occur during the tensile test: , (i) the adhesive is on both surfaces after detachment of the bonded strips (cohesive failure), (ii) the adhesive remains only on one of the surfaces (adhesive failure or delamination), and (iii) the substrate is broken due to adhesive bonding strength (substrate or adherent failure) …”

Bonded flush repairs for aerospace composite structures: A review on modelling strategies and application to repairs optimization, reliability and durability

“…Reliability analysis aims to compute the probability of failure considering uncertainties or to calculate the safety values at a given confidence and reliability level. In the recent years, reliability of bonded composite joints and uncertainties in those structures elaboration were reviewed [117,118]. Limited work was done on probabilistic assessment of flush repairs strength [119,120,121].…”

Assessment of Adhesively Bonded Joints of Similar and Dissimilar Materials: Industrial Case Study

“…In some cases, defects caused by the adhered material-and in some cases by the adhesive material-may cause a change in the mechanical performance of the joints. Factors such as cracks, voids, delamination, porosity, poor cure, adherend defects, non-uniform bondline thickness, and changes in other factors in the application can change the process [48].…”