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Table 2. Dimensions for the Smaller Cantilever Beam Specimens Cut from the Full-size Panels Thickness h (mm) Length l (mm) Width b (mm) Number of Specimens 9 600 50 33 12 600 50 20 15 900 50 35 16 900 50 25 18 1000 50 63 25 1200 50 18 Vibration Detection Test The vibration detection test was conducted using the same laboratory testing apparatus for a previous study (Guan et al . 2015). Two load sensors were used to measure the weight of the full-size WCP being tested, and a laser sensor located at the middle of the panel was used to measure the vibrational displacement. LabVIEW software (Beijing, China) was written and used to collect and process both load and vibration signals and to calculate storage modulus and loss modulus based on Eq. 2 and Eq. 3 (Xu et al . 2009). The full size panel was placed on the laboratory testing apparatus and was supported on bars at the locations, 22.4% and the 77.6% along its length direction. The testing software collected the load sensor signal and calculated the panel weight. An initial displacement was applied with both hands at one end of the panel away from the load sensor, and the hands were released from the end of the panel allowing the panel to vibrate at its free vibration state (first mode). The laser sensor recorded the vibration displacement signal used to calculate the first natural frequency ( f ) of the panel vibration and logarithmic decrement ( Δ ) of the vibrational decay. The software calculated the storage modulus ( E ’ ) and loss modulus ( E ” ) of the panel. Through R language modeling, these test data were analyzed with regression analysis using one variant linear regression analysis method, analysis of variance, and t-test (Wang 2014). Cantilever Beam Vibration Test To examine the validity of the panel vibration testing method, the cantilever beam vibration test was conducted (Yan 2010; Zhou et al. 2014b). One end of each small specimen was clamped at a length of 50 mm. The free end of the specimen was displaced an initial distance and then released, resulting in re-vibration in the first mode of the cantilever beam. The cantilever vibration displacement signal was recorded. Storage modulus and loss modulus were calculated for each cantilever specimen.
RESULTS AND DISCUSSION Dynamic Viscoelasticity for the Full-size WCPs
The average values and standard deviations (SD) for the storage modulus and loss modulus for all the panels are given in Table 3. The coefficient of variation (COV) and ratio of E ’ to E ” of the three types of panels are also given in Table 3. The values for E ’ were greater than the values for E ” for all panels tested, which was similar to previous studies of small specimens of hardboard, particleboard, and fiberboard (Moslemi 1967;
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Guan et al . (2016). “Dynamic viscoelasticity,” B io R esources 11(2), 4593-4604.
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