ICF100500PR average tensile strength and the standard deviation, the minimum and maximum tensile strength and the fibre resin adhesion strength calculated according to equation (1). For the untreated fibre it was impossible to obtain the adhesion strength because the monofilament slighted from the resin disc as soon as the test stated. Experimental tests indicated that for all the treatment conditions the weakest point was the fibre, where the fracture occurred. In other words, the resin adhesion strength is higher than the fibre tensile strength, as shown in the Table 1. For the oxygen plasma treatment, the increase in treatment time from 5s to 20s resulted in an increase in the adhesion strength while for cold plasma treatment, the increase in the treatment time decrease the adhesion strength. Scanning Electron Microscopy Fibres surface of oxygen and argon plasma treated PET subsequently exposed to the matrix cure temperature, 100ºC and the roughness profile are represented in the figures 2 to 7. a) b) 0 5 10 15 20 25 30 35 14000 15000 16000 17000 18000 19000 Pixel µm Fig. 2 – Oxygen plasma treated PET fibres for 5s post heated at 100ºC a) scanning electron microscopy of the fibre surface. b) roughness profile of the PET fibre a) b) 0 5 10 15 20 25 30 8000 10000 12000 14000 16000 18000 20000 Pixel µm Fig. 3 – Oxygen plasma treated PET fibres for 20s post heated at 100ºC a) scanning electron microscopy of the fibre surface. b) roughness profile of the PET fibre. a) b) 0 5 10 15 20 25 13000 14000 15000 16000 17000 18000 19000 20000 Pixel µm Fig. 4 – Oxygen plasma treated PET fibres for 100s post heated at 100ºC a) scanning electron microscopy of the fibre surface. b) roughness profile of the PET fibre. 8 µm 8 µm 8 µm 4
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