JEC COMPOSITES MAGAZINE - Issue #42 - July/August 2008 - 66

KNOW-HOW Raw Materials g…/… Corrosion resistance of High-Performance Glass fibres Hi gh-Perf. glass in S alt W ater HiPer-tex™ in Salt W ater Advantex® in Salt W ater C ovariant 668.55 538.01 Tab.4: Summary of the 50-year extrapolated failure strengths of rods under stress-corrosion in various environments 50 years 50 yrs strength Glass Load strength (MPa) Environments high-perf glass Reinforcement (% ultimate) (covariant vs. Advantex® regression High-perf. glass Air Advantex® High-perf. glass D.I. Water 45.8 38.4 42.1 46.2 45.9 536 556 +13% Advantex® High-perf. glass 5% salt water Advantex® 538 494 669 +24% 45.1 652 +22% Failure stress (MPa) 50 yr s 100 1 10 100 1,000 T im e in hours 10,000 100,000 1, 000, 000 Fig.9: Stress-corrosion of Advantex® and high-performance glass rods in salt water High-perf. glass Hi gh-Perf. glass inin H2SO 4 HiPer-tex™ glass H2S O 4 1000 Advantex® glass in H2SO 4 C ovariant 19.4 281 +34% 1N H2SO4 Advantex ® 17.9 281.38 209.43 50 yrs 100 1 10 100 1, 000 T ime in hours 10,000 100,000 1,000,000 Fig.10: Stress-corrosion of Advantex® and high-performance glass rods in 1N H2SO4 become available, they may slightly alleviate the slopes of the regression lines and lead to slight variations in the extrapolated long-term strengths. It is believed, however, that the current trends provide a fairly conservative indication of the extrapolated strength retentions after 50 years aging for both types of glass. Table 4 provides a summary of the extrapolations – based on the covariant regressions – of the failure strengths after 50 years under stress-corrosion. The initial static tensile strengths obtained with these rods reinforced with either Advantex® or High-Performance Glass were presented in table 2 above to serve as a reference. The rods reinforced with High-Performance Glass show 23% more initial tensile strength than the rods reinforced with Advantex® glass, a difference that appears to hold as well for long-term creep in air and for stress-corrosion in salt water. The strength retentions in salt water are also almost equal to the strength retentions in air for both glass types, which indicates that the effect of salt water on rod aging under these test conditions is nil. In de-ionized water, the strength retentions after 50 years are somewhat lower than the retentions in salt water, which confirms observations that distilled and DI water are more aggressive to composite materials than salt water. In the current results, the slopes of the regression curves for rods in DI water are slightly different and reflect a somewhat smaller difference (13%) between the two types of glass, contrasting with the results for the ISO 720-compliant hydrolysis tests mentioned earlier, which show High-Performance Glass being somewhat more resistant to hydrolysis. Even if we do need more long term stress-corrosion data before drawing conclusions about the exact 50-year strength retentions, the High-Performance Glass clearly still retains a significantly higher strength after stress-corrosion aging in water environment. In 1N sulphuric acid, the initial 23% advantage of HighPerformance Glass over Advantex® glass rises to 34% in terms of 50-year strength retention. Even if the current regression lines could be subject to slight variations as new failure points are recorded, this certainly confirms that High-Performance Glass has higher corrosion resistance to acidic environments than Advantex® glass. Failure stress (MPa) Conclusions Earlier publications have already reported that the new HighPerformance Glass has superior initial static mechanical properties and significantly better long-term dynamic fatigue performance than Advantex® glass and traditional E-glass, and all of the corrosion test results described above clearly indicate that high-performance reinforcements offer enhanced long-term corrosion resistance, not only over traditional E-glass, but also over Advantex®. Given that Advantex® boron-free E-CR glass has been known for more than 10 years as a benchmark in JEC Composites Magazine / No42 July-August 2008
JEC COMPOSITES MAGAZINE - Issue #42 - July/August 2008

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