Effects of bondline thickness on Mode-II interfacial laws of bonded laminated composite plate

Abstract

For a variety of modern industries, interfacial delamination is a critical issue for the design and application of laminated composite structures. Numerous global experimental studies have been conducted to characterize the toughness of adhesively bonded composite structures. In the recent two decades, cohesive zone models (CZMs) have been receiving intensive attentions. The local interfacial traction–separation laws as the fundamental input are crucial for the successful applications of CZMs. Several local tests have also been conducted to determine the interfacial traction–separation laws in adhesively bonded joints. However, very few tests have been employed to investigate the dependency of the local interfacial traction–separation laws on the bondline thickness, particularly, for the laminated composite joints under Mode-II loading conditions. In this work, the effects of bondline thickness on the interfacial behavior have been systematically investigated at various typical bondline thicknesses (from 0.1 to 0.8 mm). The effects of adhesive thickness on the interfacial toughness, interfacial strength, and shapes of the local interfacial traction–separation laws have also been evaluated. The test results indicated that the measured Mode-II (shear test) interfacial shear strength of the composite joints increases as the adhesive layer becomes thicker. It was found a significant dependency of the measured shapes of the Mode-II interfacial laws on the bondline thickness. Several other interesting issues were also reported in this work. This work may provide valuable baseline test data for analytical and numerical modeling of fracture and failure of laminated composite structures.