eth zurich institute for building materials (ifb), wood physics group ; [email protected] © eth...
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ETH Zurich
Institute for Building Materials (IfB), Wood Physics Group
www.ifb.ethz.ch; [email protected]
Solid wood panels – a new wood based material with high value added Peter Niemz
211/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
Outline
1. Introduction2. Modelling of Properties
2.1 Mechanical Properties• MOE• MOR
Experimental Tests2.2Physical Properties • Sorption• Swelling• Warping• Internal stresses
3. Conclusions
311/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
1. Introduction
x 1
x 2
x 3
3
32
31
13
12
1
23
2
21
(z)
(x)
(y)
What is a solid wood panel?3 or 5 layer cross laminated board (system from plywood)
Board: up to 0.5m (thickness)x3m x15m
411/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
What is a solid wood panel?• Solid wood panels represent a new multilayer material based on boards, which are glued together crosswise, in most cases spruce wood is used
• Used more and more in timber constructions providing a high value added
• The utilisation of this kind of panel gains in importance in the Swiss, German and Austrian building industry
• It is possible to vary the properties of the panels through panel configuration
511/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
Utilisation of solid wood panels as building material
611/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
Industrial prefabrication (Schilliger AG, Switzerland)
711/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
Roof constructions with solid wood panels
811/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
House built with solid wood panels
911/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
2. Modelling of Properties
2.1 Mechanical Properties
The load direction
surface layer parallel
surface layer perpendicular
(II) () MOE, pure bending
Eb(II) (N/mm2) Eb()
(N/mm2)
Shearing strength (rolling shear)
13(rol. shear) (N/mm2) 231)
(N/mm2)
Shear module
G13 (N/mm2) G231)
(N/mm2)
Bending perpendicular to the surface
1011/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
rolling shear (r-t) in middle layer
1111/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
a) Modulus of elasticity, if L/h>35 Navier-Bernoulli pure bending
33)2(
13
3)1(
1,22
1
v
v
v
vboardb
L
LE
L
LEE
E1 (1): Elastic module 1 (surface layer) with load in direction 1
E1 (2): Elastic module of layer 2 (middle layer) with load in direction 1
Eb,ges: Elastic module of cross section
Lv: Relation of lamellas-thicknesses; Lv= h (2)/h (1)
h (1): Thickness of the surface layerh (2): Thickness of the middle layer
(N/mm2)
MOE (Young’s modulus)MOE (Young’s modulus)
For surface layer orientation parallel to the longitudinal axis:
E1 (1) = EL = 11000 N/mm2; v = 15%E1 (2) = ER/T = 450 N/mm2
For surface layer orientation perpendicular to the longitudinal axis:E2 (1) = ER/T = 450 N/mm2
E2 (2) = EL= 11000 N/mm2; v = 20% (lower quality in the middle layer)
1211/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
b) Modulus of elasticity, if L/h<35 (parallel)
c
EE b
bx
1
2
2)2(
13
)1(13
Re2
)2(1
)1(13
3)1(
1
21224/
2
v
v
v
Su
v
vL
L
LG
L
GhL
EEL
LEK
c
(N/mm2)
Eb-E by pure bending
Exb _ E diminished by shearing
E = f (Bending + shearing)
1311/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
calculated influence of the lamella ratio on the MOE
(pure bending)
0
2000
4000
6000
8000
10000
12000
0.0 1.0 2.0 3.0 4.0 5.0thickness middle/surface layer
MO
E
Eb,
boar
d (N
/mm
2 )
Eb,équi(II)
Eb,équi(per)
cv=15%: surface layer parallel, cv=±20% surface layer perpendicular
1411/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
Tests on an entire board, supported at all edges
(together with the Empa/Dübendorf, Dep. of structural Engineering)
1511/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
Overview of panel tests
Lod Board structure No
boards
A 4 loads
1 10/50/10 mm 6
A 4 loads
2 25/20/25 mm 6
B 1 load, centric
1 10/50/10 mm 6
C 1 load, excentric
1 10/50/10 mm 6
Overview of panel tests
1611/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
Failure of an entire board, not failure by rolling shear
1711/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
Producer n Min[N/mm2]
Mean[N/mm2]
Max[N/mm2]
Median[N/mm2]
s[N/mm2]
x05
[N/mm2]
v[%]
Beam tests
A 70 18.7 36.5 50.4 37.6 6.18 25.5 16.9
B 78 20.3 39.9 54.4 41.1 6.71 28.0 16.8
tests at entire board
A 12 35.1 50.7 61.4 50.0 8.20 35.1 16.2
B 12 49.6 59.8 68.6 59.5 5.86 48.0 9.80
Failure stresses determined from beam and panel tests
• maximal strain tested in tensile zone from the board: 2-3%, • solid wood 1%
publication „Holz als Roh und Werkstoff“ (2007), test of different models
1811/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
2.2 Physical Properties
a) Equilibrium moisture content (calculated with Hailwood Horrobin)
1911/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
sample m2/g UFS UP UM
MHP-3-27pa 265 20.49 13.01 7.47
MHP-3-27pe 249 21.06 14.03 7.04
MHP-3-30pa 269 20.86 13.27 7.60
MHP-3-30pe 235 22.43 15.79 6.64
Surface layer: Pa: parallel; Pe: perpendicular
Calculated parameters for sorption Calculated parameters for sorption (Hailwood Horrobin)(Hailwood Horrobin)
=specific surface, up= polymolecular water, um= monomolecular water
2011/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
b) Swelling (board thickness 60mm)
• thickness 0,3-0,5%/%
• length 0,045 %/%, (20/20/20)
0,016 %/%, (10/40/10) 0,021%/%, (12/12/12/12/12)
Influence from board structure (relation surface/middle layer)
2111/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
c) Diffusion resistence
• Adhesive types tested : PVA, UF, PUR (2 types), Resorcin• 3 and 5 layer solid wood panels with different lamella ratios
0% 12%0%
0% 0%
12%
12%12%
Trockenm ittelS ilikagel
K lim a aussen:20°C / 65% rF
K lim a innen :20°C / 0% rF
Theore tische H olz feuchtigke it
V ersuchsbeg inn V ersuchsende
2211/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
y = 20.913x - 4.3976
R2 = 0.883
y = 34.993x + 74.066
R2 = 0.8972
-10.0
40.0
90.0
140.0
190.0
240.0
290.0
340.0
0 1 2 3 4 5 6
no. of gluelines
dif
us
ion
re
sis
ten
ce
μ [
-]
wet cup (100%/65%)
dry cup (0%-65%rH)
Influence of the number of gluelines (for 1K PUR)
2311/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
• The water vapour diffusion resistance is strongly related to the number of glue layers per panel thickness
• No influence on the water vapour diffusion resistance by the utilisation of different types of adhesives was found
• The diffusion resistance decreased while the EMC increased
Results diffusion resistance
2411/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
d) Internal stresses
0 10 20 30 40 50 60
Dicke (mm)
0
1
2
3
4
5
6
7
8
9
10
Feu
chte
geh
alt
(Vo
l%)
0
2
4
6
8
10
12
14
16
18
20
22
Masse%
77
177177
0 0
2828
Zeit in Tagen
Zeitlicher Verlauf der gemessenen HolzfeuchtewerteMassivholzplatte, Lagerung im Konstantklima
Moisture distribution in wood panels 2oC/90% RH
2511/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
Result:Internal cracks or warping from boards
different EMC during production and use
different EMC at both sides from the board
2611/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
Hindered shrinking of a 3-layer solid wood panel
2711/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
Modelling of warping and internal stresses in glued wood
a) example: 3-layer parquet element, oak-spruce-spruce
veneer; thickness: 14mm (3/8/3mm), diploma thesis
b) 2006 we started a PHD about internal stresses
in solid wood panels
2811/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
Moisture transfer Transfer model, Diffusion 1D
2
31
D
D
e ff.oak
e ff.p ine
u a ir = u top surface
u a ir bottom surface= u
0.1m m U F res in
0.1m m U F res in
Model in ABAQUS
x
uuD
xt
uW )(
u in itia l u final
uzh
h
oak
pine
100
.0
.1.2
plate
plateuplateuplate m
mmu
)
1001()
1001( 2
.02
.0.pine
pinepineoak
oakoakplateu
ubh
ubhm
pineoak
pineoakpine
pineoak
oak
ABAQUS hhn
hhnu
hu
hn
u
100
~1
100
~1
Iteration-method
simplification- Deff constant- without glueline- without surface material
Calculation of the influence from glue lines is possible, but material parameters are necessary
2911/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
Model A: Warping from parquetABAQUS FE Model
2
3
1 u2=0
u1= 0A (10 /14 .2 /13)
B (94 /14 .2 /13 )
u3=0
v B
A
M ois tu re exchangelim ited to the top su rface
94
Model- 3D brick Elements- 20 Points, quadr.
interpolation- mash size 2mm
Beam theory
L 1L 2L 3L e k v
N
N 2
N 3
L e kv
M
yc
1
(a) (b)
12
3
ekv
u i
ekv
M 1
M 2
M 3
beAx
2min e
x
3011/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
0 20 40 60 80 100 1200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Time [days]
Cu
pp
ing
v [m
m]
Beech
Oak
Ash
0 20 40 60 80 100 1200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Time [days]
Cu
pp
ing
v [m
m]
Beech
Oak
Ash
0 20 40 60 80 100 1200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Time [days]
Cu
pp
ing
v [m
m]
Beech
Oak
Ash
0 20 40 60 80 100 1200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Time [days]
Cu
pp
ing
v [m
m]
Beech
Oak
Ash
0 20 40 60 80 100 1200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Time [days]
Cu
pp
ing
v [m
m]
Beech SL 3.6mm
Oak SL 3.6mm
Ash SL 3.6mm
0 20 40 60 80 100 1200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Time [days]
Cu
pp
ing
v [m
m]
Angle = 30degAngle = 45 degAngle = 0 degAngle = 90 deg
0 20 40 60 80 100 1200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Time [days]
Cu
pp
ing
v [m
m]
Angle = 30degAngle = 45 degAngle = 0 degAngle = 90 deg
0 20 40 60 80 100 1200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Time [days]
Cu
pp
ing
v [m
m]
Angle = 30degAngle = 45 degAngle = 90 degAngle = 0 deg
0 20 40 60 80 100 1200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Time [days]
Cu
pp
ing
v [m
m]
0 20 40 60 80 100 1200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Time [days]
Cu
pp
ing
v [m
m]
Angle = 30degAngle = 45 degAngle = 90 degAngle = 0 deg
Influence of the grain angle in the surface layer
3111/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
0 20 40 60 80 100 1200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Time [days]
Cu
pp
ing
v [m
m]
Surface layer 2.6mm
Surface layer 3.6mm
Surface layer 4.8mm
0 20 40 60 80 100 1200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Time [days]
Cu
pp
ing
v [m
m]
Surface layer 4.8mm
Surface layer 3.6mm
Surface layer 2.6mm
0 20 40 60 80 100 1200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Time [days]
Cu
pp
ing
v [m
m]
Surface layer 2.6mm
Surface layer 3.6mm
Surface layer 4.8mm
0 20 40 60 80 100 1200
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Time [days]
Cu
pp
ing
v [m
m]
Surface layer 4.8mm
Surface layer 3.6mm
Surface layer 2.6mm
Influence of the layer thicknesses
3211/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
Model B: Stresses in the glue line and gap opening
3311/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
Stress analysis (for parquet; investigations on solid wood panels are ongoing)
Longtime study cut A-A
-15 -10 -5 0 5 10 15 20 25-1
-0.5
0
0.5
1
1.5
2
Horizontal distance to middle gap [mm]
Ver
tica
l stre
sses
S2
2 [M
Pa]
L= 0,
R,T= 0
L= 0.1,
R,T= 0.8
L= 0.3,
R,T = 1.6
L= 1.5,
R,T= 7
A ABD
B
E CC
-15 -10 -5 0 5 10 15 20 25-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
Horizontal distance to middle gap [mm]
Sh
ea
r st
ress
es
S1
2 [M
Pa
]
L= 0,
R,T= 0
L= 0.1,
R,T= 0.8
L= 0.3,
R,T = 1.6
L= 1.5,
R,T= 7
Periodic loading increases the creeping , effect delamination can occur after several summer – winter cycles.
3411/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
ongoing works
3511/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
On-line testing free swelling hindered swelling
Testing of internal stresses
3611/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
Results (spruce)
Swelling pressure
0 5 10 150
0.2
0.4
0.6
0.8
1
1.2
1.4
time [d]
pres
sure
pQ [k
N/m
m²]
Fichte (tangential)
Fichte (radial)
Fichte (longitudinal)
MDF (Plattenebene)
Dreischichtplatte
3711/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
Results (spruce)
Free swelling
0 5 10 150
0.5
1
1.5
2
2.5
time [d]
swel
ling
α [%
/%]
Fichte (tangential)Fichte (radial)Fichte (longitudinal)MDF (Plattenebene)DSP (stehende Jahrringe)DSP (liegende Jahrringe)
00
0.05
0.1
0.15
0.2
0.25
0.3
0.35
3811/2006 Peter Niemz, IfB Wood Physics Group, [email protected]
3. Conclusions
Solid wood panels have a very high value added
(producer mostly saw mills)
Properties can be calculated
Scientifically interesting field of work