STP864: Liquid Crystal Film Visualization Approach to Fracture in Composites

    Kobayashi, A
    Faculty of Engineering, Institute of Interdisciplinary Research, University of Tokyo, Tokyo,

    Suemasu, H
    Faculty of Engineering, Institute of Interdisciplinary Research, University of Tokyo, Tokyo,

    Pages: 10    Published: Jan 1985


    Abstract

    The cholesteric liquid crystals indicate a change of color in response to the temperature change by reflecting the specified wavelength of light due to the pitch alternation caused by the temperature change in the molecular layer of a liquid crystal, indicating red at lower temperature and blue at higher temperature.

    Using these liquid crystals, heat evolution during rapid crack propagation can be estimated. However, rather much errors have been introduced due to poor response of liquid crystals.

    In the present study, the heat evolution produced during rapid fracture in composites will be calculated through the improved dual-layer liquid crystal film method, which is to improve the response and to increase the accuracy in measurement of isothermal colored boundaries appeared in the liquid crystal film during fracture by obtaining two isothermals, T1 and T2, necessary for heat evolution calculation, at an earlier period of time after fracture, and by making the spacing between isothermals larger, leading toward the easier discrimination of colored boundaries, resulting in fewer errors. The results show that the time required to obtain two isothermals is reduced even by 50% for the glass-fiber composites. A videotape recorder system is used to record the colored isothermals, and velocity gages to measure the crack propagation velocity.

    Thus obtained heat evolution is correlated with the crack propagation velocity.

    Keywords:

    composite, fracture, liquid crystal, visualization, heat evolution, crack propagation velocity, temperature, dual layer, running crack front, isothermals, glass-fiber composites, colored thermal boundary front


    Paper ID: STP32811S

    Committee/Subcommittee: D30.08

    DOI: 10.1520/STP32811S


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