Fracture Testing of Honeycomb Core Sandwich Composites Using the DCB-UBM Test

Vishnu Saseendran, Christian Berggreen, Leif A. Carlsson

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    Abstract

    Face/core debonds in sandwich structures cause loss of integrity of sandwich structures. The debond problem in honeycomb core sandwich composites has not been widely studied. A suitable fracture approach coupled with experimental validation is paramount to determine the fracture resistance of the face/core interface. In this paper, a novel test-rig exploiting the double cantilever beam-uneven bending moments (DCB-UBM) concept is used to determine the fracture toughness of aircraft type honeycomb core sandwich composites as a function of the phase angle (mode-mixity), within the framework of Linear Elastic Fracture Mechanics (LEFM). The Double Cantilever Beam subjected to Uneven Bending Moments (DCB-UBM) test set-up, which was introduced by Sørensen.et.al [1], circumvents any dependency of the pre-crack length in calculation of Gc. The new test setup is based on rotary actuators which are able to slide on rails to follow the specimen’s deformation kinematics when subjected to pure rotations, as schematically shown in Figure 1. The robustness of the new test rig is demonstrated by performing pure mode-I fracture characterization of the face/core interface of a typical aircraft sandwich specimen consisting of CFRP/GFRP face sheet and a Nomex based honeycomb core. The J-integral was calculated analytically using the moments and subsequently the fracture resistance curve developed over the test domain as a function of time is averaged.
    Original languageEnglish
    Title of host publicationProceedings of the 20th International Conference on Composite Materials (ICCM20)
    Number of pages5
    PublisherICCM20 Secretariat
    Publication date2015
    Publication statusPublished - 2015
    Event20th International Conference on Composite Materials - Copenhagen, Denmark
    Duration: 19 Jul 201524 Jul 2015
    Conference number: 20
    http://iccm20.org/

    Conference

    Conference20th International Conference on Composite Materials
    Number20
    Country/TerritoryDenmark
    CityCopenhagen
    Period19/07/201524/07/2015
    Internet address

    Keywords

    • Sandwich composites
    • DCB-UBM
    • Honeycombs
    • CSDE-method

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