BS 1007-5:2010 pdf download – Advanced technical ceramics — Ceramic composites — Methods of test for reinforcements Part 5: Determination of distribution of tensile strength and of tensile strain to failure of filaments within a multifilament tow at ambient temperature 4 Principle A multifilament tow is loaded in tension. The test is performed at a constant displacement rate up to failure of all fibres. Force and cross-head displacement are measured and recorded simultaneously. When required, the longitudinal deformation is derived from the cross-head displacement using a compliance correction. From the force-displacement curve, the two-parameter Weibull distribution of the rupture strain and the distribution of the rupture strength of the filaments are obtained by sampling the non-linear parts of the curve at discrete intervals j, which correspond to an increasing number of failed filaments in the tow. The test duration is limited to reduce time dependent effects. 5 Significance and use The measurement of strain directly on the tow is difficult, so it is usually achieved indirectly via a compliance measurement that includes contributions of the loading train, grips, tab materials, etc. When it is possible to measure the tow elongation directly (by using a suitable extensometer system) this correction is not needed. The calculation of the results in Clause 10 also applies in this case by setting the load train compliance equal to zero. The evaluation method is based on an analysis of the non-linear increasing and decreasing parts of the force- displacement curve, which are caused by progressive filament failure during the test. The occurrence of these stages is promoted by a higher stiffness of the loading and gripping system. This method of evaluation is only applicable when the force-displacement curve shows these non-linear parts. The distribution of filament rupture strains does not depend on the number of filaments in the tow and is hence not affected by the number of filaments that are broken before the test. The determination of the filament strength distribution and of the elastic modulus necessitates knowledge of the initial cross sectional area of the tow. Because the number of unbroken filaments within the tow prior to the test is usually unknown, the values for the filament strength and for the elastic modulus necessarily represent lower bounds to these quantities. Also, the variation in filament diameter, which affects the strength values, is not accounted for. 6 Apparatus 6.1 Tensile testing equipment The test machine...

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