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Yan 2010; Zhou et al . 2014b). The ratios of their values were in the range of 24.94 to 77.61; the ratios of E ’ and E ” of PB panels were in the range of 24.94 to 48.77. The ratios of E ’ and E ” of MDF panels were in the range of 33.29 to 47.22, and the ratios of E ’ and E ” of PW panels were in the range of 44.43 to 77.61. The ratios of E ’ and E ” for the PW panels were higher than the PB and MDF panels. Furthermore, the COV values of E ” were greater than those of E ’ among the panels tested, which revealed that the variability of loss modulus was higher than that of the storage modulus for these three types of panels. Table 3. Storage Modulus and Loss Modulus of Full-size Wood Composite Panels Tested Using Vibration Test Method
Ratio of Storage Modulus to Loss Modulus
Storage Modulus (MPa)
Loss Modulus (MPa)
Panel Code
Average
SD
COV Average
SD
COV
PB9
2834.97 142.32 5.02% 113.65
13.55
11.92% 7.30% 7.85% 12.43% 15.17% 14.32% 6.85% 8.67% 17.89% 9.51% 12.37% 14.46%
24.94 45.09 33.25 48.77 33.29 35.27 47.22 46.32 44.43 66.90 77.61 73.79
PB16 PB18 PB25 MDF9
3631.88 141.47 3.90% 2327.62 158.35 6.80% 2637.88 119.71 4.54%
80.55 70.01 54.09
5.88 5.50 6.72
3358.80 89.13 2.65% 100.90 4405.44 66.19 1.50% 124.90 5297.37 138.89 2.62% 112.19
15.31 17.89
MDF12 MDF15 MDF18
7.69 7.25
3871.71 130.03 3.36% 3568.06 301.23 8.44% 3256.64 201.86 6.20% 4584.77 242.91 5.30% 4758.05 354.76 7.46%
83.59 80.31 48.68 59.07 64.48
PW9
14.37
PW15 PW18 PW25
4.63 7.30 9.32
Note: SD, standard deviation; COV, coefficient of variation.
Furthermore, PW panels had the lowest E ” values, indicating that PW panels exhibit lower dampening properties. This result is expected due to the cross-laminated veneer and higher stiffness properties or PW in general. Both PB and MDF panels have higher loss modulus values and are generally considered to have better damping properties for absorbing vibration energy. For example, PW panels are used to construct components in guitars and pianos that require improved resonance properties that have low loss modulus characteristics, whereas low-density MDF panels are used as room dividers to adsorb sound energy. Density and Logarithmic Decrement Relationship with Dynamic Viscoelasticity Relationship of storage modulus (E ’ ) with density Figure 1 shows the relationship between E ’ and density ( ρ ) for PB, MDF, and PW panels. The linear regression equations and the related parameters are listed in Table 4. There was a good linear relationship between E ’ and ρ for the three types of panels, and their relationships were highly significant at the 0.001 level. Moreover, the correlation coefficients between E ’ and ρ of PB panels, MDF panels, and PW panels were 0.883, 0.898, and 0.735, respectively.
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Guan et al . (2016). “Dynamic viscoelasticity,” B io R esources 11(2), 4593-4604.
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