a comparison of shear characterization of pinus pinaster ait., with the iosipescu and off-axis shear...
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A comparison of shear characterization of Pinus Pinaster Ait., with the Iosipescu and off-axis shear test methodsJ. Xaviera, N. Garridob, M. Oliveirab,
J. Moraisa,P.Camanhoc, F. Pierrond
(a) CETAV/UTAD, Vila Real, PT
(b) ESTV, Viseu, PT
(c) DEMEGI/FEUP, Porto, PT
(d) LMPF/ENSAM, Châlons-en-Champagne, FR
Composites Testing and Model Identification28-30 January 2003 – ENSAM, Châlons-en-Champagne, France
Table of contents
Introduction
Data reduction
Experimental work
Finite element analyses
Results and discussion
Conclusions
L
RT
LR
LT
RT
Introductions Wood as an orthotropic material:
Stress-strain functions in the LRT coordinate system:
LL RR TT RT LT LR
LL f11 f12 f13
RR f12 f22 f23
TT f13 f23 f33
RT f44
LT f55
LR f66 - Iosipescu shear test
- Off-axis tensile test
Identification of the shear behaviour of Pinus Pinaster Ait.:
Data reduction Iosipescu shear test:
45º 45º, , P
45º
P
O x
y
612
6
av
aav
G 6
failureideal PX
A
6av P A
6 45º 45ºav
12 12 aG CSG
Shear modulus correction:
6 6O avC 6 6
av OS
Assumption: exists a uniform distribution of shear stress and strain
through the thickness of the specimen;
The strains measured on both faces of the specimen
can be quite different due to boundary conditions
effects (Pierron (1998))
Averaging the shear strains on the two faces of the specimen
eliminates that effect.
Off-axis tensile test:
6 sin cosa P
A
6 2 sin 2 cos 2ava b c a c
612
6
av
aav
G
22 2
61 1 2 2
1 1 2 2 6
1rr r r r
X X X X X
Tsai-Hill strength criterion:
12 12aG CSG
y
, , ,a b c P PPx
a
b
c
12
Experimental work Material
Wood of maritime pine (Pinus Pinaster Ait.), of about 74 years old, from Viseu (Portugal).
Specimens:
Iosipescu specimen:
(Dimensions based on ASTM D 5379-93 Standard)
9, 10 and 8 specimens in the LR, LT and RT planes, respectively;
0/90 rosettes (CEA-06-125WT-350);
Moisture content: 10% - 12%;
Oven-dry density: 0.616 – 0,655 (g/cm3);
24
2
2 0 0
20
2 7
36°
R (T )L
16 °
Off-axis specimens:
Oblique end tabs were bounded for specimens in the
LR and LT planes:
16
66
SCotg
S
Kambala
1 2 0
20
RT
2 5
1 8°2 0
16, 14 and 14 specimens in the LR, LT and RT planes, respectively;
60-ded-delta rosettes (CEA-06-125UR-350);
Tabless specimens were used in the RT plane:
Moisture content: 10% - 12%;
Oven-dry density: 0.616 – 0,655 (g/cm3);
Mechanical testing:
INSTRON 1125 universal machine of 100 KN of capacity
Data acquisition system HBM SPIDER 8
Temperature of 23ºC (1ºC) e relative humidity of 40% (5%)
Controlled displacement rate of 1 mm/mn
Iosipescu tests:
Stationary part of fixture
Movable part of the fixture Parte móvel da amarra
Specimen
Adjustable wedges to tighten the specimen
Wedge adjusting
screw
Fixture linear guide rod
Attachement to test machine
EMSE Iosipescu Fixture
Off-axis tests:
Specimen
Gripping
arrangement
Finite element analyses Objectives of the analyses:
to acess to the stress and strain fields at the test section of the specimens;
to determine the numerical corrections factors C and S.
Wood was modeled as an linear elastic, orthotropic and homogeneous material.
Elastic properties of wood Pinus Pinaster Ait.:
EL
(GPa)ER
(GPa)ET
(GPa)LR TL RT
GLR
(GPa)GLT
(GPa)GRT
(GPa)
15.133 1.912 1.010 0.471 0.051 0.586 1.262 1.100 0.221
Numerical analysis of the Iosipescu and off-axis shear test were developed in ANSYS 6.0®.
Mesh and boundary conditions:
2-D finite element models were developed;
Quadrilateral isoparametric element PLANE82, with 8 nodes;
1800 elements and 5577 nodes.
0yu
0xu
0yu yu
yu
L
R
L
T
R
T
planeLR
planeLT
planeRT
x
y
0.1mm
Iosipescu shear test models and results:
Normalizes stress components along the vertical line, between the V-notches:
-1 ,0
-0 ,8
-0 ,6
-0 ,4
-0 ,2
0 ,0
0 ,2
0 ,4
0 ,6
0 ,8
1 ,0
-0 ,1 0 ,0 0 ,1 0 ,2 0 ,3 0 ,4 0 ,5 0 ,6 0 ,7 0 ,8 0 ,9 1 ,0 1 ,1 1 ,2
LR Plane
XY XY Y XY
X
XY
Normalizes stress components along the vertical line, between the V-notches:
LT Plane
-1 ,0
-0 ,8
-0 ,6
-0 ,4
-0 ,2
0 ,0
0 ,2
0 ,4
0 ,6
0 ,8
1 ,0
-0 ,1 0 ,0 0 ,1 0 ,2 0 ,3 0 ,4 0 ,5 0 ,6 0 ,7 0 ,8 0 ,9 1 ,0 1 ,1 1 ,2 1 ,3 1 ,4
No
rma
lize
d s
tre
ss
co
mp
on
en
ts XY XY Y XY
X
XY
Normalizes stress components along the vertical line, between the V-notches:
RT Plane
-1 ,0
-0 ,8
-0 ,6
-0 ,4
-0 ,2
0 ,0
0 ,2
0 ,4
0 ,6
0 ,8
1 ,0
-0 ,1 0 ,0 0 ,1 0 ,2 0 ,3 0 ,4 0 ,5 0 ,6 0 ,7 0 ,8 0 ,9 1 ,0 1 ,1 1 ,2
XY XY Y XY
X
XY
Normalizes shear strain under an area circumscribed by the strain-gage grid:
XY XY
LR Plane
Normalizes shear strain under an area circunscribed by the strain-gage grid:
LT Plane
XY XY
Normalizes shear strain under an area circunscribed by the strain-gage grid:
RT Plane
XY XY
Numerical corrections factors C and S:
Principalmaterialplanes
C S CS
LR 0.967 0.988 0.955 (4.5%)
LT 0.919 0.995 0.914 (8.6%)
RT 1.050 0.972 1.021 (2.1%)
xu
0zu 0yu
0 xy uu
0zu
L
TR RT
x
)(zy)(yz
xu
0 xy uu0zu
0zu
0yu
R
T L
y
z x
LRand LT plane
19089 elements
16000 nodes.
RT plane
3159 elements
1920 nodes.
Mesh and boundary conditions:
3-D finite element models
were developed;
Solid isoparametric element
SOLID64, with 24 DOF;
Off-axis tensile test models and results:
Uniformity of stress components in the LR plane:
:XY
:X
Uniformity of stress components in the LT plane:
:XZ
:X
Uniformity of stress components in the RT plane:
:Y
:YZ
Numerical corrections factors C and S:
Principal material planes
C S CS
LR 0.997 1.001 0.998 (0.2%)
LT 0.978 0.961 0.940 (6.0%)
RT 0.876 1.039 0.910 (9.0%)
Results and discussion Iosipescu tests:
Experimental data obtained for a specimen in the LR plane:
0
4
8
1 2
1 6
-1 0 0 0 0 -8 0 0 0 -6 0 0 0 -4 0 0 0 -2 0 0 0 0 2 0 0 0 4 0 0 0 6 0 0 0
N orm a l s tra in g a g e rea d in g s ()
(fro n t)
(fro n t)
(b ack )
(b ack )
45º
45º
45º
45º
Initial zone of the shear stress-strain curves, in the LR plane:
0 ,0
0 ,4
0 ,8
1 ,2
1 ,6
2 ,0
2 ,4
2 ,8
0 2 0 0 4 0 0 6 0 0 8 0 0 1 0 0 0 1 2 0 0 1 4 0 0 1 6 0 0
E n g in ee rin g sh ea r s tra in (e )
She
ar s
tres
s (M
Pa)
F ron t fac e (A ) B ack face (A ) F ron t fac e (B ) B ack face (B )
The apparent shear modulus definition:
2
2 1
a b c
r
ijG b
ij
ijO
1 ,0
1 ,1
1 ,2
1 ,3
1 ,4
1 ,5
1 ,6
1 ,7
1 ,8
1 ,9
2 ,0
0 1 2 3 4 5 6 7 8 9 1 0
S p ec im en s
Shea
r m
odul
us in
the
LR
pla
ne (
GP
a) Shear modulus, in the LR plane:
Specimen
1 1,274
2 1,516
3 1,500
4 1,543
5 1,415
6 1,258
7 1,164
8 1,457
9 1,577
MEAN 1,411
CV (%) 10,31
LRG
2%
18%
Complete shear stress-strain curves, in the LR plane:
0 ,0
2 ,0
4 ,0
6 ,0
8 ,0
1 0 ,0
1 2 ,0
1 4 ,0
1 6 ,0
1 8 ,0
2 0 ,0
2 2 ,0
0 4 0 0 0 8 0 0 0 1 2 0 0 0 1 6 0 0 0 2 0 0 0 0 2 4 0 0 0 2 8 0 0 0
A verage en g in eerin g sh ea r s tra in (e)
She
ar s
tres
s (M
Pa)
0 ,0
2 ,0
4 ,0
6 ,0
8 ,0
1 0 ,0
1 2 ,0
1 4 ,0
1 6 ,0
1 8 ,0
2 0 ,0
2 2 ,0
0 4 0 0 0 8 0 0 0 1 2 0 0 0 1 6 0 0 0 2 0 0 0 0 2 4 0 0 0 2 8 0 0 0
A verage en g in eerin g sh ea r s tra in (e)
She
ar s
tres
s (M
Pa)
Typical failure for LR principal material plane:
Local crushing
Large displacement and deformations
Cracks
1 ,1
1 ,2
1 ,3
1 ,4
1 ,5
1 ,6
1 ,7
0 1 2 3 4 5 6 7 8 9 1 0 11
S p ec im en s
Sh
ear
mod
ulu
s in
th
e L
T p
lan
e (G
Pa)
Specimen
1 1,258
2 1,287
3 1,303
4 1,420
5 1,168
6 1,091
7 1,262
8 1,160
9 1,112
10 1,144
MEAN 1,220
CV (%) 8,42
Shear modulus, in the LT plane:
LTG
0,4%
16%
0
2
4
6
8
10
12
14
16
18
0 4000 8000 12000 16000 20000 24000 28000 32000
Average engineering shear strain (e)
Shea
r st
ress
(M
Pa)
Complete shear stress-strain curves, in the LT plane:
0
2
4
6
8
10
12
14
16
18
0 4000 8000 12000 16000 20000 24000 28000 32000
Average engineering shear strain (e)
Shea
r st
ress
(M
Pa)
Typical failure for LT principal material plane:
Local crushing
Large displacement and deformations
Cracks
Shear modulus, in the RT plane:
0 ,1 8
0 ,2 0
0 ,2 2
0 ,2 4
0 ,2 6
0 ,2 8
0 ,3 0
0 ,3 2
0 ,3 4
0 ,3 6
0 ,3 8
0 ,4 0
0 ,4 2
0 1 2 3 4 5 6 7 8 9
S p ec im en
Shea
r m
odul
us in
the
RT
pla
ne (
GP
a)
19%
5%
Specimen
1 0,216
2 0,258
3 0,348
4 0,273
5 0,255
6 0,339
7 0,315
8 0,283
MEAN 0,286
CV (%) 15,85
RTG
Complete shear stress-strain curves, in the RT plane:
0 ,0
1 ,0
2 ,0
3 ,0
4 ,0
5 ,0
6 ,0
0 4 0 0 0 8 0 0 0 1 2 0 0 0 1 6 0 0 0 2 0 0 0 0 2 4 0 0 0 2 8 0 0 0 3 2 0 0 0
A verage en g in eerin g sh ea r s tra in (e)
She
ar s
tres
s (M
Pa)
1F
2F
0 ,0
1 ,0
2 ,0
3 ,0
4 ,0
5 ,0
6 ,0
0 4 0 0 0 8 0 0 0 1 2 0 0 0 1 6 0 0 0 2 0 0 0 0 2 4 0 0 0 2 8 0 0 0 3 2 0 0 0
A verage en g in eerin g sh ea r s tra in (e)
She
ar s
tres
s (M
Pa)
Two typical failure for RT principal material plane:
1F
2F
Off-axis tests:
Experimental data obtained for a specimen in the LR plane:
0
6
1 2
1 8
2 4
3 0
3 6
4 2
4 8
-2 4 0 0 -1 4 0 0 -4 0 0 6 0 0 1 6 0 0 2 6 0 0 3 6 0 0 4 6 0 0 5 6 0 0
G a g e n o rm a l stra in ()
L o a d (N )
abc
Complete shear stress-strain curves, in the LR plane:
0
2
4
6
8
1 0
1 2
1 4
1 6
1 8
0 2 0 0 0 4 0 0 0 6 0 0 0 8 0 0 0 1 0 0 0 0 1 2 0 0 0 1 4 0 0 0 1 6 0 0 0 1 8 0 0 0
E n g in eer in g sh ear stra in ()
Sh
ear
stre
ss (
MP
a)
Typical failure for a specimen in the LR plane:
0
2
4
6
8
1 0
1 2
1 4
1 6
1 8
0 2 0 0 0 4 0 0 0 6 0 0 0 8 0 0 0 1 0 0 0 0 1 2 0 0 0 1 4 0 0 0 1 6 0 0 0 1 8 0 0 0
E n g in eer in g sh ear stra in ()
Sh
ear
stre
ss (
MP
a)
Shear properties in the LR plane:
Specimens
1 1,228 3,613
2 1,316 3,360
3 1,164 3,435
4 1,111 2,903
5 1,142 4,621
6 1,031 3,583
7 1,150 3,923
8 1,104 4,637
9 1,129 4,121
10 1,050 4,064
11 1,095 3,404
12 1,089 3,725
13 1,093 3,907
14 1,031 4,802
15 1,054 3,142
16 1,017 4,604
MEAN 1,113 3,865
CV (%) 7,00 14,88
LRG LRX
0
2
4
6
8
1 0
1 2
1 4
1 6
1 8
0 2 0 0 0 4 0 0 0 6 0 0 0 8 0 0 0 1 0 0 0 0 1 2 0 0 0 1 4 0 0 0 1 6 0 0 0 1 8 0 0 0 2 0 0 0 0 2 2 0 0 0
E n gin eerin g sh ea r s tra in ()
Shea
r st
ress
(M
Pa)
Complete shear stress-strain curves, in the LT plane:
0
2
4
6
8
1 0
1 2
1 4
1 6
1 8
0 2 0 0 0 4 0 0 0 6 0 0 0 8 0 0 0 1 0 0 0 0 1 2 0 0 0 1 4 0 0 0 1 6 0 0 0 1 8 0 0 0 2 0 0 0 0 2 2 0 0 0
E n gin eerin g sh ea r s tra in ()
Shea
r st
ress
(M
Pa)
Typical failure for a specimen in the LT plane:
Shear properties in the LT plane:
Specimens
1 0,980 2,875
2 0,942 4,205
3 0,951 3,659
4 0,922 3,934
5 1,108 3,883
6 1,037 3,461
7 1,161 3,565
8 0,891 4,151
9 0,916 4,596
10 1,032 4,038
11 0,955 3,953
12 0,943 4,220
13 0,977 3,338
14 0,893 3,874
MEAN 0,979 3,839
CV (%) 8,12 11,30
LTG LTX
Complete shear stress-strain curves, in the RT plane:
0 ,0
1 ,0
2 ,0
3 ,0
0 2 0 0 0 4 0 0 0 6 0 0 0 8 0 0 0 1 0 0 0 0 1 2 0 0 0 1 4 0 0 0 1 6 0 0 0 1 8 0 0 0 2 0 0 0 0 2 2 0 0 0 2 4 0 0 0
E n g in ee rin g sh ea r s tra in ()
She
ar s
tres
s (M
Pa)
0 ,0
1 ,0
2 ,0
3 ,0
0 2 0 0 0 4 0 0 0 6 0 0 0 8 0 0 0 1 0 0 0 0 1 2 0 0 0 1 4 0 0 0 1 6 0 0 0 1 8 0 0 0 2 0 0 0 0 2 2 0 0 0 2 4 0 0 0
E n g in ee rin g sh ea r s tra in ()
She
ar s
tres
s (M
Pa)
Typical failure for a specimen in the RT plane:
Shear properties in the RT plane:
Specimens
1 0,157 0,755
2 0,133 0,790
3 0,144 0,938
4 0,149 0,834
5 0,153 0,603
6 0,157 0,584
7 0,328 0,784
8 0,142 0,779
9 0,127 0,693
10 0,140 0,565
11 0,152 0,746
12 0,124 0,750
13 0,142 0,685
14 0,126 0,675
MEAN 0,155 0,727
CV (%) 32,75 14,03
RTG RTX
Comparison of the shear properties obtained from both Iosipescu and off-axis shear test methods:
Shear modulus Shear strength
Iosipescu test 1.411 1,220 0,286 - - -
Off-axis test 1,113 0,979 0,155 3,865 3,839 0,727
Difference (%) 21,12 19,75 45,80 - - -
LRG RTGLTG LTXLRX RTX
Conclusions
The Iosipescu and off-axis shear test methods are suitable for measuring the shear moduli in all principal material planes of Pinus Pinaster Ait.;
The complete shear behaviour of Pinus Pinaster Ait., including the shear strength, can not be properly determined by the Iosipescu sheat test;
The off-axis tensile test is suitable for the complete identification of the shear stress-strain functions of Pinus Pinaster Ait.;