Open Access

ARTICLE

Influence of an Atmospheric Pressure Plasma Surface Treatment on the Interfacial Fracture Toughness on Bonded Composite Joints

J. Mohan¹, D. Carolan¹, N. Murphy¹, A. Ivankovic¹, D. Dowling¹

1 School of Electrical, Electronic and Mechanical Engineering, University College Dublin, Belfield, Dublin 4, Ireland.

Structural Durability & Health Monitoring 2007, 3(2), 81-86. https://doi.org/10.3970/sdhm.2007.003.081

Abstract

The aim of this work is to investigate the influence of a variety of plasma treatments on the surface properties of an epoxy-based composite material and to establish a relationship between these properties and the subsequent mechanical behaviour of adhesively bonded joints. To this end, specimens were subjected to three different types of plasma treatment: two short treatments (2min) of He and He plus O₂, and one long treatment (15min) of He plus O₂. The variation in surface energy of the composite specimens was examined in each case over a period of up to 3 days using contact angle measurements. Initial results show that the surface energy was increased from an untreated value of approximately 40 mJ/m² to a value of 65 mJ/m² immediately after treatment. The surface energy then fell by approximately 10 mJ/m² over the course of three days for each treatment. The composite substrates were then bonded together using an epoxy film adhesive and the Mode I fracture toughness of the joint was determined from a series of symmetric and asymmetric double cantilever beam (DCB) tests. It was found that for both test geometries the adhesive failed cohesively. As a result, the values calculated for the mean propagation strain energy release rate, G_IC, were those of the cohesive fracture toughness of the adhesive as opposed to the interfacial fracture toughness between the composite surface and adhesive.

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Keywords

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