JEC COMPOSITES MAGAZINE - Issue #42 - July/August 2008 - 63

in-plane shear tensile properties are more or less equivalent for both types of glass; the in-plane shear properties are controlled more by the fibre/matrix interface – i.e. by the sizing – and by the quality of the laminate than by the type of glass. The initial tensile strength was also tested on pultruded composite cylindrical rods (6.35 mm in diameter) in AOC’s F701 isophthalic unsaturated polyester resin. The rods’ average glass content by weight was 72% for High-Performance Glass reinforcement and 73% for Advantex®. The static properties of these rods are given in table 2. Tab.2: Initial static properties of pultruded rods Laminate type Property Avg glass content (%wt) Pultruded rods 6,35 mm diameter Avg tensile strengh (MPa) Avg tensile modulus (GPa) Back-calculated glass modulus (GPa) Advantex® High performance glass glass 73% 1172 44.4 78 72% 1447 47.5 85 Change (%) +23% +7% +9% High corrosion resistance A lot of corrosion-resistance data has been gathered since the production of boron-free E-CR glass such as Advantex® started. The data have shown that these higher-performance glass materials are more corrosion resistant than traditional E-glass [6], not only in acidic environments but also in other environments such as water, salt water, and even in cement extract [7, 8, 9, 10, 11]. However, the behaviour of these new high-performance reinforcements need to be test further in corrosive environments, because quite a few of the high-tech applications where they are likely to be used require good corrosion resistance over the long term. To that end, we undertook various types of tests in various corrosive media in comparison to Advantex® glass, the benchmark product. Even though a few of the tests are still in progress, we present the current status here as an indication of the general trends. Fibre weight loss in acids A first test simply involves measuring the fibre weight loss of bare de-sized glass fibres in acidic environment. Figures 1 show that Advantex® and High-Performance Glass undergo similar weight loss, possibly with a very slight advantage to High-Performance Glass in both sulphuric and nitric acid, whereas traditional E-glass already shows a severe weight loss of about 40% after only 24 hours in sulphuric acid at 95°C. The apparent reduction over time of E-glass fibre weight loss is due to a formation of CaSO4 crystals in the sulphuric acid solution, which could not be separated from the fibres in the filtration process. % W t Loss in 10% H2SO 4 24h 45 40 100 h 240 h The tensile test results for these pultruded rods were used to backcalculate the E-modulus of the glass fibres, giving a modulus value of 85 GPa for the High-Performance Glass and 78 GPa for the Advantex® E-CR glass, i.e. a roughly 9% difference in modulus between the two types of reinforcements. On the other hand, the modulus of the High-Performance Glass would be 17% higher than the generally accepted modulus value of 72-73 GPa for traditional E-glass. Dynamic fatigue performance Several reports [1, 2, 3] have outlined the longer dynamic-fatigue lives obtained for laminates reinforced with various types of HighPerformance Glass products compared to those reinforced with Advantex® products made with the same sizing. Layers of CDM and double-bias fabrics were infused with epoxy resin to create unidirectional and triaxial laminates, which were tested by the Risoe National Laboratory in Denmark [4, 5]. For both the unidirectional and triaxial fabrics, it was found that the slopes of the SN-curves obtained with the two types of glass were identical. On the absolute strength scale, however, the curve corresponding to the high-performance reinforcement was well above that of Advantex® reinforcement: at one million cycles, there was a 38% improvement of fatigue strength for the unidirectional fabrics and 25% for the triaxial laminates when High-Performance Glass was used instead of Advantex® glass. In terms of fatigue life span or number of cycles to failure at the same stress level, this leads to a difference of more than a decade, or a factor of at least 10 between the two types of glasses, for both UD and triaxial fabrics. 35 30 25 20 15 10 5 0 A A dvantex ® g la s s d v a n te x glass H HiP er-Tex™g la s s igHigh -Pe rf. gglass h -P e rf. la s s tra dtrad. .E g lalas s tra d E-glass . E - -g s s % W gt Loss in 10% HNO 3 24 h 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 Advantex® glass High performance glass 2 40 h Fig.1: Fibre weight loss in acidic environment at 95°C No42 July-August 2008 / JEC Composites Magazine

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

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #42 - July/August 2008