Finger-Joints and Laminated Wood. Final Report for the BFR-project
Gustafsson, Per-Johan LU and Serrano, Erik LU
(2000)
In TVSM-3000
- Abstract
- This report gives an overview and summary of research on wood-adhesive bonds performed during several years in a number of separate studies. These studies concern the mechanical testing, numerical analysis and constitutive modelling of wood-adhesive bonds in timber engineering. Applications such as finger-joints and glued-laminated timber are considered. The experimental studies include the testing of the fracture characteristics of wood-adhesive bonds. The numerical studies relate to the strength of finger-joints and laminated beams.
In the experimental studies, the complete stress-displacement response of small specimens, particularly their fracture softening behaviour beyond peak stress, was recorded. A major outcome from the... (More) - This report gives an overview and summary of research on wood-adhesive bonds performed during several years in a number of separate studies. These studies concern the mechanical testing, numerical analysis and constitutive modelling of wood-adhesive bonds in timber engineering. Applications such as finger-joints and glued-laminated timber are considered. The experimental studies include the testing of the fracture characteristics of wood-adhesive bonds. The numerical studies relate to the strength of finger-joints and laminated beams.
In the experimental studies, the complete stress-displacement response of small specimens, particularly their fracture softening behaviour beyond peak stress, was recorded. A major outcome from the experiments is that wood-adhesive bonds can behave in a fracture-softening manner, and that it is possible to record this under stable conditions.
In one of the numerical studies the finite element method was employed to analyse the stress distribution around zones of low stiffness in a laminated beam. A fracture mechanics analysis was also performed of the delamination of a laminated beam. The results show that the often made assumption of a stress redistribution taking place around weak zones is not necessarily true. Another finding is that the delamination of an initially cracked glulam beam tends to be increasingly dominated by mode II failure as the lamination thickness decreases.
In another study, also related to finger-joints and laminated beams, the finger-joint failure in a glulam beam was simulated using a nonlinear fictitious crack model with stochastic properties. The results show the proposed approach to be able to account for such phenomena as the size effect and the laminating effect. Another observation is that finger-joint fracture energy, i.e. the ductility, has a major influence on lamination and beam strength. The influence of bondline defects on the tensile strength of a finger-joint was also investigated. It was demonstrated that even a small defect in the form of a glueline void, can have a relatively strong influence on the tensile strength. It was also demonstrated that the strength of finger-joints is largely inuenced by the outermost finger.
Finally, an interface model based on damage mechanics is suggested for the modelling of wood-adhesive interfaces. This model accounts for joint dilatation and post-cracking friction. Also, a homogenisation scheme is presented for combining the proposed model with ordinary plasticity models for the adhesive bulk. This homogenisation procedure is based on assumptions regarding the stress and strain gradients typical of thin bondlines.
(Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/0f18def1-84c8-4c53-bf30-78b1c72d3d4b
- author
- Gustafsson, Per-Johan
LU
and Serrano, Erik
LU
- organization
- publishing date
- 2000-12
- type
- Book/Report
- publication status
- published
- subject
- keywords
- Adhesive, Bending strength, Constitutive modelling, Damage, Experiment, Finger-joint, Finite Element Method, Fracture mechanics, Glued-laminated timber, Joint, Laminated beams, Laminating effect, Numerical simulation, Size effect, Stress distribution, Tensile strength, Test method, Wood
- in
- TVSM-3000
- issue
- TVSM-3054
- pages
- 19 pages
- publisher
- Division of Structural Mechanics, LTH
- language
- English
- LU publication?
- yes
- id
- 0f18def1-84c8-4c53-bf30-78b1c72d3d4b
- date added to LUP
- 2023-08-17 17:54:21
- date last changed
- 2023-10-16 09:47:33
@techreport{0f18def1-84c8-4c53-bf30-78b1c72d3d4b,
abstract = {{This report gives an overview and summary of research on wood-adhesive bonds performed during several years in a number of separate studies. These studies concern the mechanical testing, numerical analysis and constitutive modelling of wood-adhesive bonds in timber engineering. Applications such as finger-joints and glued-laminated timber are considered. The experimental studies include the testing of the fracture characteristics of wood-adhesive bonds. The numerical studies relate to the strength of finger-joints and laminated beams.<br/><br/>In the experimental studies, the complete stress-displacement response of small specimens, particularly their fracture softening behaviour beyond peak stress, was recorded. A major outcome from the experiments is that wood-adhesive bonds can behave in a fracture-softening manner, and that it is possible to record this under stable conditions.<br/><br/>In one of the numerical studies the finite element method was employed to analyse the stress distribution around zones of low stiffness in a laminated beam. A fracture mechanics analysis was also performed of the delamination of a laminated beam. The results show that the often made assumption of a stress redistribution taking place around weak zones is not necessarily true. Another finding is that the delamination of an initially cracked glulam beam tends to be increasingly dominated by mode II failure as the lamination thickness decreases.<br/><br/>In another study, also related to finger-joints and laminated beams, the finger-joint failure in a glulam beam was simulated using a nonlinear fictitious crack model with stochastic properties. The results show the proposed approach to be able to account for such phenomena as the size effect and the laminating effect. Another observation is that finger-joint fracture energy, i.e. the ductility, has a major influence on lamination and beam strength. The influence of bondline defects on the tensile strength of a finger-joint was also investigated. It was demonstrated that even a small defect in the form of a glueline void, can have a relatively strong influence on the tensile strength. It was also demonstrated that the strength of finger-joints is largely inuenced by the outermost finger.<br/><br/>Finally, an interface model based on damage mechanics is suggested for the modelling of wood-adhesive interfaces. This model accounts for joint dilatation and post-cracking friction. Also, a homogenisation scheme is presented for combining the proposed model with ordinary plasticity models for the adhesive bulk. This homogenisation procedure is based on assumptions regarding the stress and strain gradients typical of thin bondlines.<br/>}},
author = {{Gustafsson, Per-Johan and Serrano, Erik}},
institution = {{Division of Structural Mechanics, LTH}},
keywords = {{Adhesive; Bending strength; Constitutive modelling; Damage; Experiment; Finger-joint; Finite Element Method; Fracture mechanics; Glued-laminated timber; Joint; Laminated beams; Laminating effect; Numerical simulation; Size effect; Stress distribution; Tensile strength; Test method; Wood}},
language = {{eng}},
number = {{TVSM-3054}},
series = {{TVSM-3000}},
title = {{Finger-Joints and Laminated Wood. Final Report for the BFR-project}},
url = {{https://lup.lub.lu.se/search/files/155165671/web3054.pdf}},
year = {{2000}},
}