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The effect of the densification process on dowel tensile performance with different types of glues


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Figure 1

Cutting pattern of heart planks from a log
Cutting pattern of heart planks from a log

Figure 2

Hydraulic press used in densification processes
Hydraulic press used in densification processes

Figure 3

Experiment samples
Experiment samples

Figure 4

Dowel tensile test
Dowel tensile test

Figure 5

Tensile performance according to wood species, densification ratio, dowel diameter and glue type
Tensile performance according to wood species, densification ratio, dowel diameter and glue type

Figure 6

Interaction of all parameters
Interaction of all parameters

Pre-compression dimensions of draft test samples

Compression ratio Dimensions (mm)
length (longitudinal direction) width (tangent direction) thickness (radial direction)
50% 800 10 20
75% 800 10 40

Test parameters

Poplar 800 × 10 × 8 PVAc Control 6 Eastern spruce 800 × 10 × 8 PVAc Control 6
50% 6 50% 6
75% 6 75% 6
D-VTKA Control 6 D-VTKA Control 6
50% 6 50% 6
75% 6 75% 6
800 × 10 × 10 PVAc Control 6 800 × 10 × 10 PVAc Control 6
50% 6 50% 6
75% 6 75% 6
D-VTKA Control 6 D-VTKA Control 6
50% 6 50% 6
75% 6 75% 6

Tensile performance test results according to wood species

Wood species* Tensile performance (kg/cm2)X – HG
Eastern spruce 182.50a
Poplar 173.66b
Densification ratio**
75% 191.4a
50% 175.5b
Control 167.4c
Dovel diameter***
8 mm diameter dowel 195.11a
10 mm diameter dowel 161.05b
Types Glue****
PVAc glue 185.92a
D-VTKA glue 170.24b

Compression ratios in air dry moisture after densification processes

Wood Densification conditions Thickness before compression Thickness after compression Press thickness Compression ratio Std.
Poplar 140°C 50% 20 mm 10.14 mm 10 mm 47.80% 0.16
140°C 75% 40 mm 10.57 mm 10 mm 73.57% 0.58
Eastern spruce 140°C 50% 20 mm 10.22 mm 10 mm 48.90% 0.31
140°C 75% 40 mm 10.86 mm 10 mm 72.85% 0.51

Descriptive Statics

Parameters Tensile performance (kg/cm2)*
densification dowel diameter (mm) glue type poplar eastern spruce
control 8 PVAc 177.302 139.665
8 D-VTKA 176.582 206.168
10 PVAc 171.640 134.923
10 D-VTKA 154.833 178.178
50% 8 PVAc 227.615 183.760
8 D-VTKA 226.072 192.995
10 PVAc 160.153 187.593
10 D-VTKA 110.105 115.582
75% 8 PVAc 177.780 189.280
8 D-VTKA 203.208 222.127
10 PVAc 159.003 303.547
10 D-VTKA 120.853 136.205

Technical properties of the hydraulic press

Press temperature Compression ratio
Pressure capacity 100 ton – 250 Bar
Temperature range 0–250°C
Pressure piston stroke 500 mm
Table size 60 × 60 cm
Motion auto/manual, 8–11 mm/sec.

Density values and moisture content of dowels

Densification ratio Density values (g/cm3) Moisture content (%)
poplar eastern spruce poplar eastern spruce
Control 0.390 0.401 8.218 8.925
50% 0.508 0.540 4.558 6.485
75% 0.622 0.629 4.381 5.187

Tensile performance (kg/cm2) test results according to quadruple (Duncan Test) interactions

Wood species + Densification ratio + + Diameter of dowel + Glue type X-HG (kg/cm2)
P + d50% + 8mm + PVAc 227.6a
P + d50% + 8mm + Dv 226.1a
Es + d75% + 8mm + Dv 222.1a
Es + C+8mm + Dv 206.2b
P + d75% + 8mm + Dv 203.2bc
P + d75% + 8mm + PVAc 196.6bcd
Es + d50% + 8mm + Dv 193.0cde
Es + d75% + 8mm + PVAc 189.3cde
Es + d50% + 10mm + PVAc 187.6cde
Es + d50% + 8mm + PVAc 183.8cdef
Es + d75% + 10mm + PVAc 177.8def
Es + C+10mm + Dv 178.2defg
P + C + 8mm + PVAc 177.3defg
P + C + 8mm + Dv 176.6efg
Es + C + 10mm + PVAc 171.6efg
P + d50% + 10mm + PVAc 160.2fgh
P + d75% + 10mm + PVAc 159.0fghi
P + C + 10mm + Dv 154.8ghi
Es + C + 8mm + PVAc 139.7hij
Es + d75% + 10mm + Dv 136.2hij
Es + C + 10mm + PVAc 134.9ij
P + d75% + 10mm + Dv 120.9jk
Es + d50% + 10mm + Dv 115.6jk
P + d50% + 10mm + Dv 110.1k

Densification process

Densification
Press temperature Compression ratio Time
140°C 50% press heating + 15 minutes
75% press heating + 15 minutes

Tensile performance test results according to binary interactions

Wood + Densification X-HG Densification + Diameter X-HG Densification + Glue X-HG
Es + d75% 212.8a d50% + 8mm 207.6a d75% + PVAc 212.1a
P + d50% 181.0b d75% + 8mm 202.8a d50% + PVAc 189.8b
P 170.1bc d75% + 10mm 179.9b C + Dv 178.9bc
Es + d50% 170bc C + 8mm 174.9b d75% + Dv 170.6cd
P + d75% 169.9bc C + 10mm 159.9c d50% + Dv 161.2de
Es 164.7c d50% + 10mm 143.4d C + PVAc 155.9e
LSD = ±11.09 LSD = ±11.12 LSD = ±19.21

Variance analysis of tensile performance test

Source Degree of freedom Sum of square Mean of square F α < 0.05
Wood species (A) 1 2,811.562 2,811.562 7.3974 0.0075*
Densification (B) 2 14,244.143 7,122.071 18.7386 0.0000*
AB 2 21,040.921 10,520.461 27.6799 0.0000*
Diameter (C) 1 41,772.206 41,772.206 109.9050 0.0000*
AC 1 15,980.963 15,980.963 42.0468 0.0000*
BC 2 16,775.502 8,387.751 22.0686 0.0000*
ABC 2 9,586.050 4,793.025 12.6107 0.0000*
Glue (D) 1 8,853.084 8,853.084 23.2930 0.0000*
AD 1 43.263 43.263 0.1138 0.0000*
BD 2 28,015.219 14,007.609 36.8548 0.0000*
ABD 2 20,149.924 10,074.962 26.5078 0.0000*
CD 1 42,854.177 42,854.177 112.7517 0.0000*
ACD 1 9,539.593 9,539.593 25.0992 0.0000*
BCD 2 15,928.969 7,964.484 20.9550 0.0000*
ABCD 2 9,423.694 4,711.847 12.3971 0.0000*
Error 120 45,609.062 380.076
Total 143 302,628.332
eISSN:
2199-5907
ISSN:
0071-6677
Sprache:
Englisch
Zeitrahmen der Veröffentlichung:
4 Hefte pro Jahr
Fachgebiete der Zeitschrift:
Biologie, Botanik, Medizin, Veterinärmedizin