Voids in fiber reinforced thermosetting polymers: Formation, structure and mechanical behaviour

Ivan V. Sergeichev, Eduard S. Batyrshin, Almir I. Mullayanov, Svyatoslav S. Chugunov, Sergey G. Abaimov, Iskander Sh Akhatov

    Research output: Contribution to conferencePaperpeer-review

    Abstract

    Modern technological operations require production of void-free laminates with the optimal degree of resin cure, using fiber-reinforced composite materials with thermosetting matrix as a basis. Formation of voids in composite laminate is a complex physical process, which depends on an interaction of heat transfer, resin flow, pre-form compaction and cure process. When composites were first introduced, formation of large voids was inevitable, since parameters of manufacturing process (i.e., temperature/pressure-time profiles) were selected via empirical methods. To disadvantage of such an approach, the parameters were restricted to a small range of process variables; they could not be generalized for different materials and geometries; finally, the method was expensive and time consuming. The shortcomings of empirical approach could be eliminated with the use of validated analytical and numerical models of composite material, which allow optimization of the process variables. The present work is focused on experimental research of void formation during impregnation of unidirectional glass-fiber reinforcement with thermosetting polymer resin. A number of samples featuring various degree of porosity and different void structure were prepared with liquid composite molding (LCM) technique. The designed mold allows an impregnation of the dry unidirectional preform under pressure gradient, created by pressure difference at inlet and outlet of the mold. Composite samples were fabricated at a variety of pressure conditions at inlet and outlet of the mold, replicating injection and infusion processes. Void distribution and volume fraction of voids in the sample volume were studied using optical microscopy and computed micro-tomography techniques.

    Original languageEnglish
    Publication statusPublished - 2017
    Event21st International Conference on Composite Materials, ICCM 2017 - Xi'an, China
    Duration: 20 Aug 201725 Aug 2017

    Conference

    Conference21st International Conference on Composite Materials, ICCM 2017
    Country/TerritoryChina
    CityXi'an
    Period20/08/1725/08/17

    Keywords

    • Computed micro-tomography
    • Glass-fiber reinforcement
    • Liquid composite molding
    • Microscopy
    • Polymer matrix composite
    • Voids

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