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    <title language="eng">Evolution of CFRP stress cracks observed by in situ X-ray refractive imaging</title>
    <abstract language="eng">Modern air-liners and rotor blades of wind turbines are basically made of fiber reinforced plastics (FRP). Their failure heavily impairs the serviceability and the operational safety. Consequently, knowledge of the failure behavior under static and cyclic loads is of great interest to estimate the operational strength and to compare the performance of different materials. Ideally, the damage evolution under operational load is determined with in-situ non-destructive testing techniques. Here, we report on in-situ synchrotron X-ray imaging of tensile stress induced cracks in carbon fiber reinforced plastics (CFRP) due to inter fiber failure. An in-house designed compact-tensile testing machine with a load range up to 15 kN was integrated into the beam path. Since conventional radiographs do not reveal sufficient contrast to distinct cracks due to inter fiber failure and micro cracking from fiber bundles, the Diffraction Enhanced Imaging technique (DEI) is applied in order to separate primary and scattered (refracted) radiation by means of an analyzer crystal. In the laboratory, scanning X-ray refraction topography of CFRP has been applied long before but it comes along with several disadvantages: the long total measuring time hampers real time (in-situ) measurements and the required small beam size hinders end-to-end imaging. The introduced technique overcomes both drawbacks. Imaging and tensile test rig are run unsynchronized at the greatest possible frame rate (0.7 s-1 at 28.8 µm pixel size) and smallest possible strain rate (5.5∙10-4 s-1). For 0°/90° non-crimped fabrics (ncf) the first inter fiber cracks occurred at 380 MPa (strain 0.7 %). Prior to failure at about 760 MPa (strain 2.0 %) we observe the evolution of a nearly equidistant 1 mm grid of cracks running across the entire sample in the fully damaged state before total failure.</abstract>
    <enrichment key="eventName">41st Risø International Symposium on Materials Science - Materials and Design for Next Generation Wind Turbine Blades</enrichment>
    <enrichment key="eventPlace">Online meeting</enrichment>
    <enrichment key="eventStart">07.09.2020</enrichment>
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    <author>Andreas Kupsch</author>
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      <language>eng</language>
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      <value>X-ray refraction</value>
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    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Diffraction Enhanced Imaging</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Carbon Fiber Reinforced Plastics</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>In situ tensile test</value>
    </subject>
    <subject>
      <language>eng</language>
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      <value>Crack evolution</value>
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    <collection role="ddc" number="620">Ingenieurwissenschaften und zugeordnete Tätigkeiten</collection>
    <collection role="institutes" number="">5 Werkstofftechnik</collection>
    <collection role="institutes" number="">5.3 Polymere Verbundwerkstoffe</collection>
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  <doc>
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    <title language="eng">Evolution of CFRP stress cracks observed by in situ X-ray refractive imaging</title>
    <abstract language="eng">Modern air-liners and wind turbine rotor blades are made up primarily of fiber reinforced plastics. Failure of these materials heavily impairs the serviceability and the operational safety. Consequently, knowledge of the failure behavior under static and cyclic loads is of great interest to estimate the operational strength and to compare the performance of different materials. Ideally, the damage evolution under operational load is determined with in-situ non-destructive testing techniques. Here, we report in-situ synchrotron X-ray imaging of tensile stress induced cracks in carbon fiber reinforced plastics due to inter-fiber failure. An inhouse designed compact tensile testing machine with a load range up to 15 kN was integrated into the beamline. Since conventional radiographs do not reveal sufficient contrast to distinguish cracks due to inter-fiber failure and micro cracking from fiber bundles, the Diffraction Enhanced Imaging (DEI) technique is applied in order to separate primary and scattered (refracted) radiation by means of an analyzer crystal. This technique allows fast measurements over large fields-of-view and is ideal for in-situ investigations.</abstract>
    <enrichment key="eventName">12th BESSY@HZB User Meeting 2020</enrichment>
    <enrichment key="eventPlace">Online meeting</enrichment>
    <enrichment key="eventStart">10.12.2020</enrichment>
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    <author>Andreas Kupsch</author>
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      <language>eng</language>
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      <value>Carbon Fiber Reinforced Plastics</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Crack evolution</value>
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    <subject>
      <language>eng</language>
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      <value>Diffraction Enhanced Imaging</value>
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      <language>eng</language>
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      <value>In situ tensile test</value>
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      <language>eng</language>
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    <id>51506</id>
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    <publishedYear>2020</publishedYear>
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    <pageFirst>012035-1</pageFirst>
    <pageLast>012035-9</pageLast>
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    <volume>942</volume>
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    <publisherPlace>Bristol, UK</publisherPlace>
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    <title language="eng">Evolution of CFRP stress cracks observed by in situ X-ray refractive imaging</title>
    <abstract language="eng">Modern air-liners and wind turbine rotor blades are made up primarily of fiber reinforced plastics. Failure of these materials heavily impairs the serviceability and the operational safety. Consequently, knowledge of the failure behavior under static and cyclic loads is of great interest to estimate the operational strength and to compare the performance of different materials. Ideally, the damage evolution under operational load is determined with in situ non-destructive testing techniques. Here, we report in-situ synchrotron X-ray imaging of tensile stress induced cracks in carbon fiber reinforced plastics due to inter-fiber failure. An inhouse designed compact tensile testing machine with a load range up to 15 kN was integrated into the beamline. Since conventional radiographs do not reveal sufficient contrast to distinguish cracks due to inter-fiber failure and micro cracking from fiber bundles, the Diffraction Enhanced Imaging (DEI) technique is applied in order to separate primary and scattered (refracted) radiation by means of an analyzer crystal. This technique allows fast measurements over large fields-of-view and is ideal for in-situ investigations. Imaging and the tensile test are run at the highest possible frame rate (0.7 s-1 ) and the lowest possible strain rate (5.5∙10-4 s -1 ). For 0°/90° non-crimp fabrics, the first inter-fiber cracks occur at 380 MPa (strain 0.8 %). Prior to failure at about 760 MPa (strain 2.0 %), we observe the evolution of nearly equidistant (1 mm distance) cracks running across the entire sample in the fully damaged state.</abstract>
    <parentTitle language="eng">IOP conference series: Materials science and engineering</parentTitle>
    <identifier type="doi">10.1088/1757-899X/942/1/012035</identifier>
    <identifier type="issn">1757-8981</identifier>
    <identifier type="issn">1757-899X</identifier>
    <identifier type="urn">urn:nbn:de:kobv:b43-515060</identifier>
    <enrichment key="date_peer_review">29.04.2021</enrichment>
    <licence>Creative Commons - CC BY - Namensnennung 4.0 International</licence>
    <author>Andreas Kupsch</author>
    <author>Volker Trappe</author>
    <author>Bernd R. Müller</author>
    <author>Giovanni Bruno</author>
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      <language>eng</language>
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    <subject>
      <language>eng</language>
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      <value>Carbon Fiber Reinforced Plastics</value>
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      <language>eng</language>
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