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DIN Standards Committee Materials Testing

Overview

This document (EN 1007-5) has been prepared by Technical Committee CEN/TC 184 "Advanced technical ceramics", the secretariat of which is held by BSI. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by September 2010, and conflicting national standards shall be withdrawn at the latest by September 2010. This document supersedes EN 1007-5:2003. EN 1007 "Advanced technical ceramics - Ceramic composites - Methods of test for reinforcements" consists of 7 parts: - Part 1: Determination of size content - Part 2: Determination of linear density - Part 3: Determination of filament diameter and cross-section area - Part 4: Determination of tensile properties of filaments at ambient temperature - Part 5: Determination of distribution of tensile strength and of tensile strain to failure of filaments within a multifilament tow at ambient temperature - Part 6: Determination of tensile properties of filaments at high temperature - Part 7: Determination of the distribution of tensile strength and of tensile strain to failure of filaments within a multifilament tow at high temperature. This part of the European Standard specifies the conditions, apparatus and procedure for determining the distribution of tensile strength and tensile strain to failure of ceramic filaments in multifilament tows at ambient temperature. This part of the European Standard applies to tows of continuous ceramic filaments, which are assumed to act freely and independently under loading, and behave linearly elastic up to failure. A multifilament tow shall be loaded in tension. The test shall be performed at a constant displacement rate up to failure. Force and cross-head displacement shall be measured and recorded simultaneously. When required, the longitudinal deformation shall be 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 shall be 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 shall be limited to reduce time dependent effects. 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, and so on. These contributions shall be taken into account for proper evaluation. 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. At DIN the Committee responsible for this standard is NA 062-02-94 AA "Prüfung von Hochleistungskeramik - Keramische Verbundwerkstoffe" ("Testing of advanced technical ceramics - Ceramic composites").

Document: references other documents

Responsible national committee

NA 062-02-94 AA - Testing of advanced technical ceramics - Ceramic composites  

Responsible european committee

CEN/TC 184/SC 1 - Advanced technical ceramics - ceramic composites