JEC COMPOSITES MAGAZINE - Issue #42 - July/August 2008 - 64

KNOW-HOW Raw Materials Hydrolysis resistance Glass-fibre samples were also submitted to hydrolysis resistance tests in compliance with ISO 720 standards [12], in which crushed glass particles of a specific size are immersed in distilled water at 121°C for 24 hours and the leaching water then neutralized with 0.02N HCl. The lower the amount of HCl required, the more hydrolysis resistant the glass is. The results indicate that High-Performance Glass falls in the best hydrolysis resistance class (HGA1), whilst Advantex® glass and E-glass fall in the HGA2 class (table 3). Tab.3: Hydrolysis resistance classes (ISO 720) HGA1 (best) Maximum volume of 0.02N HCI per gram of glass Advantex® glass High-performance glass 0.08ml 0.10 ml HGA2 0.85ml 0.14ml Hi gh-Perfor m. glass in H 4 HiPer-tex™ glass in H2SO2SO4 2. 8 2. 6 2. 4 2. 2 Advantex® glass in H2SO 4 T im e = f (% Strain) g…/… Corrosion resistance of High-Performance Glass fibres HGA3 1.50ml Fig.4: Strain-corrosion jig for flat samples Flexural strain-corrosion of flat laminates Dry roving was radial wound over a flat mandrel (figure 3) and impregnated with MGS L135i epoxy resin using the vacuum-assisted infusion process to create unidirectional laminates. The impregnation was conducted under vacuum at an absolute pressure of 35 mbar between glass plates, leading to a perfectly constant thickness and producing almost perfect laminates with an extremely low void content (below 0.7%), and a glass content of around 79% by weight. After cure and post-cure, samples were cut and submitted to 4-point bending on specially designed stainless-steel jigs where various levels of constant deflections were applied. Due precaution was taken to apply the same level of deflection on each deflection jig and on several samples together (figure 4). These bending jigs were then immersed into 5% H2SO4 and time to failure was recorded for each sample. 2. 0 1. 8 1. 6 1. 4 1. 2 1. 0 0. 8 0. 6 0. 4 0. 2 0. 0 1 10 100 1 , 000 Hours 10 , 000 100 , 000 1 , 000 , 000 0 .8 0 % 1.12 % 26 m onths 50 yrs Fig. 5: Strain-corrosion of flat laminates in 5% H2SO4 For each one of the high-performance and Advantex® glasses, 33 specimens were tested under various strain levels and the time to failure of each specimen was recorded. The results are plotted in figure 5, together with the least square regression curves. It is recognized that failure points beyond 10,000 hours should be obtained to allow extrapolation of the regression lines to 50 years, in compliance with usual strain-corrosion standards. Such extrapolations were made here, however, to provide an indication of the glass performance trends. The strain-corrosion results obtained with High-Performance Glass lead to a 50-year strain exceeding 1.1%, whereas with Advantex® roving, the 50-year strain is 0.80%. Advantex® glass is itself an E-CR glass, and already well known for its significantly superior strain-corrosion performance compared to traditional E-glass. In this case, the strain at failure after 50 years with High-Performance Glass is about 40% higher than with Advantex® glass. Stress-corrosion of pultruded rods Test procedure Fig.3: Winding on a flat mandrel A test procedure was designed to allow reliable comparison of the combined influence of glass type and environmental factors on the long-term strength of composite rods. The procedural principle is to JEC Composites Magazine / No42 July-August 2008

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

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