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Energy absorption of SMC/balsa sandwich panels with geometrical triggering features
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.ORCID iD: 0000-0002-9207-3404
2010 (English)In: Composite structures, ISSN 0263-8223, Vol. 92, no 11, 2676-2684 p.Article in journal (Refereed) Published
Abstract [en]

The influence of triggering topologies on the peak load and energy absorption of sandwich panels loaded in in-plane compression is investigated. Sandwich panels with different geometrical triggering features are manufactured and tested experimentally. The damage initiation in panels with grooves is investigated using finite element models. As expected the investigated triggering features reduce the extreme load peaks. A less expected result is that the plateau load following peak load tends to be higher for panels with triggering features. Both results are favourable for the crash performance of panels in vehicle applications. For panels containing no or few grooves the peak load seems to be governed by principles of fracture mechanics while initial failure in panels with a higher number of grooves appears to be controlled by the average stress.

Place, publisher, year, edition, pages
Oxford, UK: Elsevier , 2010. Vol. 92, no 11, 2676-2684 p.
Keyword [en]
Sandwich; Energy absorption; Edgewise compression; Damage triggering
National Category
Applied Mechanics Composite Science and Engineering Other Materials Engineering
URN: urn:nbn:se:kth:diva-11156DOI: 10.1016/j.compstruct.2010.03.018ISI: 000279301300007ScopusID: 2-s2.0-77953356942OAI: diva2:236440

QC 20150729

Available from: 2009-09-23 Created: 2009-09-23 Last updated: 2015-07-29Bibliographically approved
In thesis
1. In-plane Compressive Response of Sandwich Panels
Open this publication in new window or tab >>In-plane Compressive Response of Sandwich Panels
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The high specific bending stiffness of sandwich structures can with advantage be used in vehicles to reduce their weight and thereby potentially also their fuel consumption. However, the structure must not only meet the in-service requirements but also provide sufficient protection of the vehicle passengers in a crash situation. The in-plane compressive response of sandwich panels is investigated in this thesis, with the objective to develop a methodology capable of determining if the structural response is likely to be favourable in an energy absorption perspective. Experiments were conducted to identify possible initial failure and collapse modes. The initial failure modes of sandwich panels compressed quasi-statically in the in-plane direction were identified as global buckling, local buckling (wrinkling) and face sheet fracture. Global buckling promotes continued folding of the structure when compressed beyond failure initiation. Face sheet fracture and wrinkling can promote collapse in the form of unstable debond crack growth, stable end-crushing or ductile in-plane shear collapse. Both the unstable debond crack propagation and the stable end-crushing are related to debond crack propagation, whereas the ductile in-plane shear mode is related to microbuckling of the face sheets.

The collapse behaviour of sandwich configurations initially failing due to wrinkling or face sheet fracture was investigated, using a finite element model. The model was used to determine if the panels were likely to collapse in unstable debond propagation or in a more stable end-crushing mode, promoting high energy absorption. The collapse behaviour is mainly governed by the relation between the fracture toughness of the core and the bending stiffness and strength of the face sheets. The model was successfully used to design sandwich panels for different collapse behaviour. The proposed method could therefore be used in the design process of sandwich panels subjected to in-plane compressive loads.During a crash situation the accelerations on passengers must be kept below life threatening levels. The extreme peak loads in the structure must therefore be limited. This can be achieved by different kind of triggering features.Panels with either chamfered face sheets or with grooves on the loaded edges were investigated in this thesis. The peak load was reduced with panels incorporating either of the two triggering features. Another positive effect was that the plateau load following failure initiation was increased by the triggers. This clearly illustrates that triggers can be used to promote favourable response in sandwich panels.

Vehicles are harmful to the environment not only during in-serve use, but during their entire life-cycle. By use of renewable materials the impact on the environment can be reduced. The in-plane compressive response of bio-based sandwich panels was therefore investigated. Panels with hemp fibre laminates showed potential for high energy absorption and panels with a balsa wood core behaved particular well. The ductile in-plane shear collapse mode of these panels resulted in the highest energy absorption of all investigated sandwich configurations.


Place, publisher, year, edition, pages
Stockholm: KTH, 2009. xi, 27 p.
Trita-AVE, ISSN 1651-7660 ; 2009:67
Sandwich, Finite Element Analysis (FEA), Fracture, In-plane compression
National Category
Other Materials Engineering Condensed Matter Physics
urn:nbn:se:kth:diva-11160 (URN)978-91-7415-447-4 (ISBN)
Public defence
2009-10-26, Sal F3, Lindstedtsvägen 26, Stockholm, 10:15 (English)
QC 20100728Available from: 2009-10-06 Created: 2009-09-23 Last updated: 2010-07-28Bibliographically approved

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