| Source | SDHM, Vol. 3, No. 2, pp. 81-86 |
| Download | Full length paper in PDF format. Size = 111,623 bytes |
| Keywords | Atmospheric pressure plasma, surface energy, composites, adhesives, asymmetric double cantilever beam (DCB) tests. |
| 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 O$_{2}$, and one long treatment (15min) of He plus O$_{2}$. 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/m$^{2}$ to a value of 65 mJ/m$^{2}$ immediately after treatment. The surface energy then fell by approximately 10 mJ/m$^{2}$ 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$_{\textnormal {IC}}$, were those of the cohesive fracture toughness of the adhesive as opposed to the interfacial fracture toughness between the composite surface and adhesive. |