Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Energy Absorption of Sandwich Panels Subjected to In-plane Loads
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
2006 (English)In: 8th Biennial ASME Conference on EngineeringSystems Design and Analysis, Torino, Italy, 4-7 July, 2006: Volume 3: Dynamic Systems and Controls, Symposium on Design and Analysis of Advanced Structures, and Tribology, 2006, 739-747 p.Conference paper, Published paper (Refereed)
Abstract [en]

Theenergy absorption mechanisms of sandwich panels subjected to in-plane compressionare studied. Quasi-static experiments are performed and analysed in orderto support the development of a modelling strategy for failureinitiation and propagation in sandwich panels. The test specimens consistof balsa wood cores and glass-fibre reinforced polyester faces. Duringcompression of a tested panel, the displacement field on oneouter face is measured using a digital speckle photography (DSP)equipment. The absorbed energy is related to debonding, delamination andcrushing of the face sheets and crushing of the core.At initial failure, the load drops dramatically and is thenrelatively constant during continued compression. The energy per unit lengthnecessary for propagation of the damage is considerably lower thanfor damage initiation. Assuming that the damage propagation is uniformthrough the thickness of the panels a simple model ofdamage growth is developed. Calibration of the model is howeverdubious due to the large scatter in the experimental results.The studied material shows damage mechanisms favourable for efficient energyabsorption but the behaviour is far from being optimal.

Place, publisher, year, edition, pages
2006. 739-747 p.
Keyword [en]
Computer simulation; Delamination; Energy absorption; Loads (forces); Mathematical models; Structural
National Category
Composite Science and Engineering
Identifiers
URN: urn:nbn:se:kth:diva-11152DOI: 10.1115/ESDA2006-95771ISI: 000249558200084Scopus ID: 2-s2.0-33845767479ISBN: 0-7918-4250-9 (print)OAI: oai:DiVA.org:kth-11152DiVA: diva2:236433
Conference
8th Biennial ASME Conference on Engineering Systems Design and Analysis, Torino, Italy, 2006
Note

QC 20100728

Available from: 2009-09-23 Created: 2009-09-23 Last updated: 2016-05-16Bibliographically approved
In thesis
1. Strength of Sandwich Panels Loaded in In-plane Compression
Open this publication in new window or tab >>Strength of Sandwich Panels Loaded in In-plane Compression
2007 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

The use of composite materials in vehicle structures could reduce the weight and thereby the fuel consumption of vehicles.

As the road safety of the vehicles must be ensured, it is vital that the energy absorbing capability of the composite materials are similar to or better than the commonly used steel structures. The high specific bending stiffness of sandwich structures can with advantage be used in vehicles, provided that the structural behaviour during a crash situation is well understood and possible to predict. The purpose of this thesis is to identify and if possible to describe the failure initiation and progression in in-plane compression loaded sandwich panels.

An experimental study on in-plane compression loaded sandwich panels with two different material concepts was conducted. Digital speckle photography (DSP) was used to record the displacement field of one outer face-sheet surface during compression. The sandwich panels with glass fibre preimpregnated face-sheets and a polymer foam core failed due to disintegration of the face-sheets from the core, whereas the sandwich panels with sheet molding compound face-sheets and a balsa core failed in progressive end-crushing. A simple semi-empirical model was developed to describe the structural response before and after initial failure.

The postfailure behaviour of in-plane compression loaded sandwich panels was studied by considering the structural behaviour of sandwich panels with edge debonds. A parametrical finite element model was used to determine the influence of different material and geometrical properties on the buckling and postbuckling failure loads. The postbuckling failure modes studied were debond crack propagation and face-sheet failure. It could be concluded that the postbuckling failure modes were mainly determined by the ratio between the fracture toughness of the face-core interface and the bending stiffness of the face-sheets.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. xi, 16 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2007:73
Keyword
sandwich, in-plane compression, energy absorption, debond, postbuckling
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-4558 (URN)978-91-7178-814-6 (ISBN)
Presentation
2007-12-14, D31, Lindstedtsvägen 17, Kungliga Tekniska Högskolan, Stockholm, 10:15
Opponent
Supervisors
Note
QC 20101111Available from: 2007-11-25 Created: 2007-11-25 Last updated: 2010-11-11Bibliographically approved
2. 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.
Series
Trita-AVE, ISSN 1651-7660 ; 2009:67
Keyword
Sandwich, Finite Element Analysis (FEA), Fracture, In-plane compression
National Category
Other Materials Engineering Condensed Matter Physics
Identifiers
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)
Opponent
Supervisors
Note
QC 20100728Available from: 2009-10-06 Created: 2009-09-23 Last updated: 2010-07-28Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Authority records BETA

Hallström, Stefan

Search in DiVA

By author/editor
Lindström, AndersHallström, Stefan
By organisation
Lightweight Structures
Composite Science and Engineering

Search outside of DiVA

GoogleGoogle Scholar

doi
isbn
urn-nbn

Altmetric score

doi
isbn
urn-nbn
Total: 114 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf