Effects of Cyclic Boil-Dry Treatment on Properties of Bintangor (Callophyllum Sp) Laminated Veneer Lumber
This study evaluates the physical and mechanical properties of bintangor (Callophyllum sp) laminated veneer lumber (LVL) under cyclic boil-dry (CBD) treatment. The properties studied were thickness swelling (TS), linear expansion (LE), water absorption (WA), delamination, bending shear and static...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2004
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/342/1/549627_T_FH_2004_3.pdf |
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| Summary: | This study evaluates the physical and mechanical properties of bintangor (Callophyllum
sp) laminated veneer lumber (LVL) under cyclic boil-dry (CBD) treatment. The
properties studied were thickness swelling (TS), linear expansion (LE), water absorption
(WA), delamination, bending shear and static bending (moduli of elasticity and rupture).
LVLs of 1220 x 2440 mm in size were manufactured on a commercial LVL production
line. The thicknesses of the veneers were set at 3.1 and 4.1 mm, producing 17- and 13-ply
LVL panels respectively. A total of two hundred and sixty four large specimens were
prepared for static bending (50 x 90 x 1000 mm) and bending shear (40 x 50 x 300 mm).
To determine the effect of sample size, seventy two small static bending specimens (12.5 x 50 x 305 mm) were cut from the 13-ply LVL. The small and large static bending
specimens were tested according to American Society for Testing and Materials D 143
and AS/NZ 4063:1992 Timber – Stress-graded – in-grade strength and stiffness
evaluation respectively. Bending shear was determined according to AS/NZ 4357. In all
cases, the CBD treatment procedure was conducted by taking consideration the size
factor so that each specimen would experience similar degree of heating regime. The
analysis of variance (ANOVA) shows that the TS, delamination, stiffness (MOE) and
strength (MOR) were significantly influenced by the specimen size, veneer thickness and
number of CBD cycle while bending shear were significantly influenced by the number
of CBD cycle and veneer thickness. The most severely degraded were specimens that
have been treated for 10 cycles. LVL produced from thinner veneers (3.1 mm) as in 17-ply LVL, was apparently more stable where acceptably low TS, WA, LE and percent
delamination were recorded resulting in low reductions in stiffness, strength and shear
after CBD treatment. There was a negative relationship between delamination and
bending shear after CBD treatment where 17-ply LVL showed a curvilinear trend whilst
13-ply LVL showed a linear relationship. The study also found inspite having the same degree of heating regime, larger specimens experienced much more severe strength
degradation which mainly caused by shear failure at the center (middle layers) of the
LVL panel. The shorter span used for the large specimens (1: 10) was observed to be
responsible for the shearing effect that subsequently reduced the MOE and MOR values
in this study. The outdoor aging revealed that MOE of smaller specimens was badly
degraded (40%) compared to the large specimens (22%) after six months of outdoor
aging. Large and small specimens produced from 13-ply LVL (thicker veneers)
experienced more strength reduction under 6 months outdoor aging (28%) compared to
10 cycles of CBD treatment (24%). MOE and MOR after any one of 2, 5 or 10 cycles of
CBD treatment showed good correlation with MOE and MOR after 3 and 6 months of outdoor aging. |
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