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Leffler, Karin
Publications (3 of 3) Show all publications
Leffler, K., Alfredsson, K. S. & Stigh, U. (2007). Shear behaviour of adhesive layers. International Journal of Solids and Structures, 44(2), 530-545
Open this publication in new window or tab >>Shear behaviour of adhesive layers
2007 (English)In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 44, no 2, p. 530-545Article in journal (Refereed) Published
Abstract [en]

An experimental method to determine the complete stress versus deformation relation for a thin adhesive layer loaded in shear is presented. The method is based on a classic specimen geometry; the end-notch flexure specimen. The experiments are evaluated using an inverse method. First, the variation of the energy release rate with respect to the shear deformation at the crack tip is measured during an experiment. Then the traction–deformation relation is derived using an inverse method. The theory is based on the path-independence of the J-integral and considers the effects of a flexible adhesive layer.

Quasi-static experiments on three different specimen geometries are performed using a servo-hydraulic testing machine. The experiments give consistent results. This shows that the traction–deformation relation can be taken as independent of the dimensions of the adherends. Thus, the constitutive relation can be considered as a property of the adhesive layer. The deformation process at the crack tip is also monitored during the experiments by the use of a digital camera attached to a microscope.

Place, publisher, year, edition, pages
Elsevier, 2007
Keywords
Inverse method, Adhesive layer, Cohesive law, J-Integral, Experimental method
National Category
Engineering and Technology
Research subject
Technology
Identifiers
urn:nbn:se:his:diva-1969 (URN)10.1016/j.ijsolstr.2006.04.036 (DOI)000243145300010 ()2-s2.0-33750960843 (Scopus ID)
Available from: 2008-04-16 Created: 2008-04-16 Last updated: 2017-12-12Bibliographically approved
Leffler, K. & Stigh, U. (2005). On the existence of a unique stress-deformation relation for an adhesive layer loaded in shear. In: 11th International Conference on Fracture (ICF11), Turin, Italy 20-25 March 2005: Volume 5. Paper presented at 11th International Conference on Fracture (ICF11), Turin (Italy) - March 20-25, 2005 (pp. 3763-3768). Curran Associates, Inc.
Open this publication in new window or tab >>On the existence of a unique stress-deformation relation for an adhesive layer loaded in shear
2005 (English)In: 11th International Conference on Fracture (ICF11), Turin, Italy 20-25 March 2005: Volume 5, Curran Associates, Inc., 2005, p. 3763-3768Conference paper, Published paper (Refereed)
Abstract [en]

An experimental method to determine the complete stress vs. deformation relation for a thin adhesive layer loaded in shear is presented. The experiments are performed by use of a classical specimen geometry, i.e. the end-notch flexure specimen, though the experiments are evaluated based on a novel inverse technique. With this  technique,  the  instantaneous  energy  release  rate  is  first  evaluated  by  use  of  a  theory  for  the  specimen based  on  the  Euler-Bernoulli  beam  theory.  Effects  of  a  flexible  adhesive  layer  are  considered  in  an approximate way. From the energy release rate, the stress-deformation relation is evaluated using an inverse method.  In  order  for  the  theory  to  be  valid,  the  adherends  of  the  specimen  are  only  allowed  to  deform elastically.  Quasi-static   experiments  are  performed  using  a  servo-hydraulic  testing  machine.  In  the experiments, the displacement of the loading point is gradually increased to obtain a constant velocity of the shear  deformation  at  the  crack  tip.  Formation  of  micro-cracks  and  the  propagation  of  a  macro-crack  are monitored during the experiments by use of a CCD-camera attached to a microscope. By varying the heights of the adherends, the size of the process zone in front of the crack tip changes from about 200 to 400 times the thickness of the adhesive layer. The results of the experiments give a fracture toughness of 2.5 kJ/m 2 , a critical  shear  deformation  of  0.13  mm,  and  a  maximal  strength  of  30  MPa  independent  of  the  specimen geometry.  The  experiments  show  consistent  results.  The  results  show  that  if  the  process  zone  is  large  as compared  to  the  thickness  of  the  adhesive layer,  the  shear  stress  –  shear  deformation  relation  can  be considered as a constitutive property of the adhesive layer.

Place, publisher, year, edition, pages
Curran Associates, Inc., 2005
Identifiers
urn:nbn:se:his:diva-7118 (URN)2-s2.0-84869784288 (Scopus ID)978-1-61782-063-2 (ISBN)
Conference
11th International Conference on Fracture (ICF11), Turin (Italy) - March 20-25, 2005
Note

http://www.icf11.com/about/centrabout.asp

http://www.icf11.com/FinalReport18062008.pdf

Available from: 2013-02-04 Created: 2013-02-04 Last updated: 2017-11-27Bibliographically approved
Leffler, K. (2005). Shear Behaviour of Adhesive Layers. (Licentiate dissertation). Chalmers tekniska högskola
Open this publication in new window or tab >>Shear Behaviour of Adhesive Layers
2005 (English)Licentiate thesis, monograph (Other scientific)
Abstract [en]

An experimental method to determine the complete stress versus deformation relation for a thin adhesive layer loaded in shear is presented. The work is based on a classical specimen geometry, i.e. the end-notch flexure specimen (ENF-specimen) and the experiments are evaluated based on an inverse method. By studying the energy balance at the crack tip an expression for the energy release rate is derived. The theory considers the effects of a flexible adhesive layer and is based on beam theory. From the energy release rate the stress-deformation relation is derived using the inverse method.

Quasi-static experiments are performed using a servo-hydraulic testing machine. The deformation process at the crack tip is monitored during the experiments by use of a CCD-camera attached to a microscope. The method requires differentiation of the energy-deformation relation, therefore a Monte-Carlo simulation is performed to investigate how small errors in the data acquisition system affects the final stress-deformation relation. Small errors in the measurement of the force and shear deformation give small effects on the final stress-deformation relation.

Experiments on three different geometries of the specimen are performed. The experiments give consistent results. It is shown that if the process zone in front of the crack tip is large, then the stress-deformation relation does not depend on the dimensions of the adherends. Thus, the constitutive relation can be considered to be a property of the adhesive layer.

Place, publisher, year, edition, pages
Chalmers tekniska högskola, 2005. p. 59
Series
Department of Applied Mechanics, Chalmers University of Technology, ISSN 1652-8565 ; 2005:15
Keywords
Adhersive layer, shear, ENF-specimen, stress-deformation relation, experimental method, J-integral, inverse method
National Category
Mechanical Engineering
Research subject
Technology
Identifiers
urn:nbn:se:his:diva-1630 (URN)
Presentation
(English)
Available from: 2007-08-03 Created: 2007-08-03 Last updated: 2017-11-27
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