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Residual strength prediction of impacted composite sandwich structures

Wetzel, Anja and Baaran, Jens (2008) Residual strength prediction of impacted composite sandwich structures. In: Proceedings of the 2nd International Conference on Buckling and Postbuckling Behaviour of Composite Laminated Shell Structures. 2nd International Conference on Buckling and Postbuckling Behaviour of Composite Laminated Shell Structures, 2008-09-03 - 2008-09-05, Braunschweig, Deutschland.

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Abstract

The paper presents two methods for predicting the in-plane compression strength of impact damaged sandwich structures. For developing these methods uniaxial in-plane compression tests of impact damaged unsymmetrical sandwich coupons are conducted. The specimens were made of two CFRP face sheets of different thickness and an embedded honeycomb core. Low velocity impacts from 1 J up to 15 J caused varying amounts of core and face sheet damage and a dent in the impacted face sheet. While increasing the in-plane compression in the residual strength tests, the dent grew in depth and transverse to the loading direction until final failure of the impacted face sheet occurred. This phenomenological observation is reproduced in computational simulations. The simulations use either an efficient finite element model or a semi-analytical Ritz approach including non-linear displacement-strain relations and progressive damage growth in the core. For the latter stress-based failure criteria and stiffness degradation models are applied. Residual strength criteria are developed depending on the numerical solver. The comparison of simulation and test results demonstrates that the presented methods are able to predict the damage tolerance of unsymmetrical sandwich structures. For damages due a high-energy impact the simulations show that the face sheet damage has to be included in the model. Including the face sheet damage into the semi-analytical model increases the computational time tremendously. Therefore, the semi-analytical model should be used only for impact damages with negligible face sheet damage.

Document Type:Conference or Workshop Item (Speech)
Title:Residual strength prediction of impacted composite sandwich structures
Authors:
AuthorsInstitution or Email of Authors
Wetzel, AnjaFERCHAU Engineering GmbH, Aviation, Bremen, 28199, Germany
Baaran, JensUNSPECIFIED
Date:September 2008
Journal or Publication Title:Proceedings of the 2nd International Conference on Buckling and Postbuckling Behaviour of Composite Laminated Shell Structures
Editors:
EditorsEmail
DLR Braunschweig, UNSPECIFIED
Status:Published
Keywords:residual strength, sandwich structures, finite elements, damage mechanics
Event Title:2nd International Conference on Buckling and Postbuckling Behaviour of Composite Laminated Shell Structures
Event Location:Braunschweig, Deutschland
Event Type:international Conference
Event Dates:2008-09-03 - 2008-09-05
Organizer:DLR Braunschweig, Institut für Faserverbundleichtbau und Adaptronik
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Aeronautics
HGF - Program Themes:Aircraft Research
DLR - Research area:Aeronautics
DLR - Program:L AR - Aircraft Research
DLR - Research theme (Project):L - Structures & Materials
Location: Braunschweig
Institutes and Institutions:Institute of Composite Structures and Adaptive Systems > Structural Mechanics
Deposited By: Doris Ries
Deposited On:09 Sep 2008
Last Modified:27 Apr 2009 15:12

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