Effect of an Atmospheric Pressure Plasma Treatment on the Mode I Fracture Toughness of a Co-Cured Composite Joint

Abstract

In this study, the surface of a composite prepreg was treated using an atmospheric pressure plasma in an attempt to improve the fracture toughness of a co-cured joint system. Three gas mixtures were investigated; helium, helium/nitrogen, and helium/oxygen. The processing parameters of the system were varied to obtain the maximum increase in surface energy of the prepreg. A He/O₂ plasma was found to be the most efficient treatment, giving the largest increase in surface energy in the shortest time. Co-cured joints were then fabricated using prepreg that had been treated with various plasmas. A modest 15–18% increase in the Mode I fracture toughness was achieved. However, the locus of failure remained interfacial. It was also observed that a He/O₂ plasma treatment could be detrimental to joint toughness for long treatment times.

KEYWORDS:

• Composites
• Fracture mechanics
• Surface treatment by excited gases (e.g., flame, corona, plasma)

ACKNOWLEDGEMENTS

The materials provided by Cytec Engineered Materials (CEM) are gratefully acknowledged.

Notes

Note the increase in percentage oxygen.

Note the increase in oxygen containing functional groups.

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