The thermo-mechanical performance of glass-fibre reinforced Polyamide 66 during glycol-water hydrolysis conditioning

Injection moulded glass-fibre reinforced polyamide 66 composites based on two glass fibre products with different sizing formulations and unreinforced polymer samples have been characterised by dynamic mechanical analysis and unnotched Charpy impact testing both dry as moulded and during conditioning in a glycol-water mixture at 70°C for a range of times up to 400 hours. Simultaneously weight and dimension changes of these materials have been recorded. The results reveal that hydrothermal ageing in glycol-water mixtures causes significant changes in the thermo-mechanical performance of these materials. It is shown that mechanical performance obtained after conditioning at different temperatures can be superimposed when considered as a function of the level of fluid absorbed by the composite polymer matrix

Instrument Systems Analysis and Verification Facility (ISAVF) users guide

The ISAVF facility is primarily an interconnected system of computers, special purpose real time hardware, and associated generalized software systems, which will permit the Instrument System Analysts, Design Engineers and Instrument Scientists, to perform trade off studies, specification development, instrument modeling, and verification of the instrument, hardware performance. It is not the intent of the ISAVF to duplicate or replace existing special purpose facilities such as the Code 710 Optical Laboratories or the Code 750 Test and Evaluation facilities. The ISAVF will provide data acquisition and control services for these facilities, as needed, using remote computer stations attached to the main ISAVF computers via dedicated communication lines

Characterisation of the transverse thermoelastic properties of natural fibres used in composites

To predict the properties of a composite, it is necessary to identify the properties of the constituent materials, especially those of the fibre. Mechanical properties of natural fibres (NF) are anisotropic and cannot be characterised in the same way as isotropic materials. Therefore further characterisation of the natural fibres is needed to determine their transverse thermo-mechanical behaviour. An understanding of the thermoelastic anisotropy of natural fibres is important for defining their performance in potential composite applications. In this study, thermoelastic properties of flax and sisal fibres where determined through a combination of experimental measurements and micromechanical modelling. Dynamic mechanical thermal analysis and thermal mechanical analysis techniques were employed to characterise model unidirectional NF-epoxy composites over a range off-axis loading angles. These results were input into a number of micromechanical and semi-empirical models to determine the transverse and longitudinal thermoelastic properties of the fibre. The results confirm the high degree of anisotropy in properties of the flax and sisal fibres

Development of a digital electronic rebalance loop for a dry tuned-rotor two degree-of-freedom gyroscope

Digital electronic rebalance loops were designed and implemented in brassboard form to capture both X and Y axes of the Kearfott Gyroflex. The loops were width-modulated binary types using a 614.4 kHz keying signal and a 2.4 kHz sample frequency. The loops were designed for a torquing rate of 2 deg/sec (70.6 mA torquing current) and a data resolution of 23.4 milli-arc-sec per data pulse. Design considerations, implementation details, and preliminary experimental results are presented

Regeneration of thermally recycled glass fibre for cost-effective composite recycling : increasing the strength of thermally conditioned glass fibres using cost effective recover treatments

The paper reports an extensive study on the regenerating performance of thermally treated glass fibres using two different chemically based treatments routes. The effectiveness of these two different treatments was investigated on strength recovery of glass fibres thermally treated with the conditions imitating composite recycling technology. The regenerated strength levels of these ReCoVeRed fibres must also be further protected and maintained by the use of standard fibre sizing technology similar to standard glass fibre products. Consequently, the effect on fibre strength of the combination of our ReCoVeR treatments with the standard silane coatings was also studied. Significant increase of fibre strength was obtained through the ReCoVeR and coatings treatments, achieving up to 200% increase in fibre strength in comparison with the glass fibre thermally treated

Kinetics of dissolution of glass fibre in hot alkaline solution

Kinetics of the dissolution of E-glass fibres in alkaline solutions was investigated. To allow an accurate determination of conversion, glass fibres were immersed individually in the corrosive medium and the diameter change was measured with the use of a scanning electron microscope. Few studies have been reported in the literature on the kinetics of E-glass fibre dissolution or the dissolution of individual fibres. The kinetic study of E-glass fibre dissolution in alkaline solutions is scarcely reported in literature, and no investigation is so far conducted regarding individual fibres. Our experimental results fit well in the zero order and shrinking cylinder models, suggesting either the diffusion of hydroxide ions through the solution or the glass fibre etching itself were rate limiting steps. The rate constant for the reaction of glass fibre with alkaline solution at 95 °C was found to be between 1.3 x 10-4 and 4.3 x 10-4 g/(m2.s). The reaction order (n) was determined as 0.31–0.49 with respect to the alkaline solution, and the activation energy was 58−79 kJ/mol