ICF100500PR surface degradation on the fibres subjected to argon plasma. Roughness profile represented in figure 7b for argon plasma treatment 100s and post heated at 100°C confirms the significant reduction in the average tensile strength. CONCLUSIONS • The plasma treatments produce a significant effect on the fibre resin adhesion strength; • For the untreated fibre it was impossible to obtain the adhesion strength due to the inertness and the low energy of PET fibres surface; • For all treatment conditions the weakest point was the fibre, where the fracture occurred attesting that the fibre/resin adhesion strength is higher than the fibre tensile strength; • The distance of roughness interval (Dri) was a parameter obtained through the use of Scion Image Program and used to associate fibre surface condition after cold plasma treatment and average tensile strength. For oxygen and argon cold plasma treated fibres, Dri is lower in comparison to the untreated fibres which explains decrease in the tensile strength. In some cases, higher roughness depth enhance stress concentration effects and influences mechanical behaviour. Acknowlegdements The authors wish to thank the support provided by FAPESP through the process number 97/01160-7. REFERENCES 1. WEIDNER et al, J. applied pol. Sci. : Part A: Pol. che,. 36, (1998) 1639-1648. 2. GOULD, S.A. C., SCHIRALDI, D. A. & OCCELLI, M. L. J. applied pol. sci. (1998) 1237-1243. 3. BLACKMAN, B. R. K., KINLOCH, A. J. & WATTS, J. F. Composites, 25/5 (1994) 332-341. 4. KILL, G., HUNTER, D. H. & McINTYRE, N. S. J. pol. sci.: part A pol. che., 34 (1996) 2299-2310. 5. JANG, B. Z. Comp. sci. Tech. 44 (1992) 333-349. 6. GAO, S. & ZENG, Y. J. applied pol. sci. 47, (1993) 2065-2071. 7. OCCHIELLO, E. et. al. Composites. 23/3 (1992) 193-200. 8. INAGAKI, N., TASAKA, S. & GOTO, Y. J. applied pol. Sci. 66(1997) 77-84. 6
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