LVL density Results and Discussion for sengon and jabon LVL

51 A strong relationship between density of solid wood and of LVLs with bending properties was observed by numerous authors Kilic et al. 2006; Shukla and Kamdem 2007 ; H’ng et al. 2010. In general, LVL density of jabon had higher values than sengon. This fact was caused by the higher density of jabon veneer compared to sengon veneers. The average veneer densities of sengon were 287.0 kgm -3 unboiled sengon and 318.4 kgm -3 boiled sengon. The average veneer densities of unboiled and boiled jabon were 395.3 and 406.9 kgm -3 , respectively. Figure 28 LVL density from pith to bark made of unboiled and boiled sengon a and jabon b veneers

4.6.2 Effect of lathe check on glue bond strength of LVL

The average glue bond strengths of the LVL increased from pith to bark for unboiled and boiled of sengon and jabon Figure 29a-b. The average glue bond strength of unboiled and boiled sengon type I were 35.8, 38.2 kgcm -2 , respectively. Otherwise the average glue bond strengths of unboiled and boiled sengon type II were 39.8 and 43.1 kgcm -2 , respectively Figure 29a. The average glue bond strengths of jabon LVL were 39.8 kgcm -2 unboiled type I, 45.5 kgcm -2 boiled type I, 43.2 kgcm -2 unboiled type II and 50.7 kgcm -2 boiled type II Figure 27b. Figure 29 Glue bond strength of LVL from pith to bark made of unboiled and boiled sengon a and jabon b 300 350 400 450 500 550 600 1 2 3 4 5 6 7 8 L VL d en sity kg m -3 Segmented rings from pith to bark Unboiled sengon type I Boiled sengon type I Unboiled sengon type II Boiled sengon type II a 400 450 500 550 600 1 2 3 4 5 6 7 8 L VL d en sity kg m -3 Segmented rings from pith to bark Unboiled jabon type I Boiled jabon type I Unboiled jabon type II Boiled jabon type II b 20 40 60 80 1 2 3 4 5 6 7 8 Glu e bo nd s tren gth kg cm -2 Segmented rings from pith to bark Unboiled sengon type I Boiled sengon type I Unboiled sengon type II Boiled sengon type II 20 40 60 80 1 2 3 4 5 6 7 8 Glu e bo nd s tr en gth kg cm -2 Segmented rings from pith to bark Unboiled jabon type I Boiled jabon type I Unboiled jabon type II Boiled jabon type II a b 52 The results suggest that increasing proportion of veneer near the pith would decrease the glue-lines capacity to withstand concentrated shear stresses, thus resulting in higher amounts of glue-line failure and a reduction in percent wood failure. However, as the proportion of veneer near bark increased, percent glue- line failure decreased. These results are in line with Darmawan et al. 2015 who found the same phenomena on 2 mm LVL made of sengon veneers. Figure 30 The correlation between frequency of lathe check and the LVL glue bond strength of unboiled and boiled sengon LVL a and jabon LVL b These phenomena were not caused only by veneer density, but also the frequency of lathe check Figure 30a-b. The glue bond strength had a statistically significant, negative correlation to lathe check frequency. Its correlation coefficients according to the lines in Figure 30a-b are summarized in Table 10. The results show that the regression coefficients for the glue bond strength linear equation depicted by boiling treatment and layout. The more lathe check frequency in veneers, would result in the lower glue bond strength of the LVL for unboiled and boiled. Table 10 Linear regression equation and determination coefficients according to Figure 30 Y = glue bond strength, X = frequency of lathe check, R 2 = determination coefficient Linear regression R 2 Unboiled sengon type I Y = 55.02 – 7.72X 0.79 Boiled sengon type I Y = 51.98 – 7.73X 0.93 Unboiled sengon type II Y = 61.42 – 8.69X 0.81 Boiled sengon type II Y = 60.03 – 9.47X 0.89 Unboiled jabon type I Y = 51.77 – 0.29 X 0.60 Boiled jabon type I Y = 58.85 – 0.38 X 0.70 Unboiled jabon type II Y = 59.94 – 4.10X 0.64 Boiled jabon type II Y = 77.73 – 7.74X 0.89 20 40 60 80 1 2 3 4 5 6 7 Glu e bo nd s tr en gth kg cm -2 Frequency lathe check per cm veneer length Unboiled sengon type I Boiled sengon type I Unboiled sengon type II Boiled sengon type II 20 40 60 80 1 2 3 4 5 6 7 Glu e bo nd s tr en gth kg cm -2 Frequency of lathe check per cm veneer length Unboiled jabon type I Boiled jabon type I Unboiled jabon type II Boiled jabon type II a b