21 research outputs found

    Structural performance of fibrous plaster. Part 1:Physical and mechanical properties of hessian and glass fibre reinforced gypsum composites

    Get PDF
    Hessian fibre-reinforced gypsum, known as fibrous plaster, is a common material used for the manufacture of decorative features, including ceilings and walls in historic buildings, such as theatres and ballrooms, since the mid 19th century. It is still fabricated with modern materials for the decoration of new buildings in the UK, the Middle East and elsewhere. Following several recent failures of historic fibrous plaster ceilings in England, there is an urgent need to understand how these materials perform. There is no previous scientific investigation into the physical and mechanical properties of this material.As an initial experimental study, the microstructure of low and high density gypsum plaster were evaluated together with traditional hessian fabrics and modern glass fabrics, which are supplementing or replacing hessian fabrics. The chemical and physical characteristics were evaluated by X-ray diffraction,mercury intrusion porosimetry and dynamic vapour sorption. For the hessian, fibre density was measured and single filament strength measured to ascertain the effect of long-term ageing in new and historic material. Flexural tests were performed on gypsum plaster reinforced with different configurations of hessian and glass fabric reinforcements. Single filaments from historic hessian were weaker than filaments from new hessian and the larger scatter in strength was demonstrated using a Weibull distribution function. High density gypsum absorbed less moisture (0.2%) than low density gypsum (1%), as expected, but the jute fibres in the hessian absorbed more than 20% of the moisture. High density gypsum was considerably stronger than low density material, and random glass mats as reinforcement resulted in the highest flexural strengths and ability to yield to higher strains, due to enhanced interfacial bonding. This work will have high impact by providing a much needed basis for understanding the long-term degradation of fibrous plaster systems

    Strong photo-induced refractive index changes in RF-sputtered tantalum oxide planar waveguides

    No full text
    Large negative UV-induced index changes (~ -0.01) have been measured in sputtered tantalum oxide planar waveguides using an optical fibre probe capable of accurately monitoring both the magnitude and the sign of the index change

    Electric-field-induced periodic domain inversion in Nd<sup>3+</sup>-diffused LiNbO<sub>3</sub>

    No full text
    The authors report the first demonstration of electric-field-induced periodic poling in neodymium-indiffused lithium niobate. The fidelity of patterning is as good as with undoped samples, and the poling field required is smaller. This novel combination of two techniques for manipulation of the optical properties of lithium niobate makes possible an extended range of active devices
    corecore