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loss modulus reflects the damping properties of the material. Both moduli are important reference indicators for determining the mechanical properties of the material itself that affects the use of WCPs. Reports on the dynamic viscoelasticity on full-size WCPs are relatively rare. Current test equipment, such as dynamic mechanical analyzers (DMA), are generally limited to smaller samples with a thickness of no more than 10 mm. For thinner materials, the dynamic viscoelasticity of two types of hardboard have been tested using the vibrating reed method by means of non-destructive dynamic vibrations (Moslemi 1967). A cantilever beam apparatus was developed for determining dynamic viscoelasticity of wood or composite materials, and it quickly and accurately determines the dynamic viscoelasticity of small specimens of wood or WCPs (Yan 2010; Zhou et al. 2014b). Currently, there are no test methods or equipment that have been useful for determining the dynamic viscoelasticity for full-size WCPs. Based on “free-free” vibration theory and support conditions, a laboratory test apparatus was developed to determine the dynamic MOE for full-size WCPs (Guan et al. 2015). This work is a continuation of initial research to determine the dynamic viscoelasticity of full-size WCPs using this apparatus. The objective of this paper is to examine the feasibility and validity of the vibration testing method for assessing dynamic viscoelasticity for full-size WCPs. Vibration detection tests were performed on 194 pieces of full-size WCPs. The panels tested included particleboard (PB), medium density fiberboard (MDF), and plywood (PW), over a range of thicknesses and densities. To examine the validity of this method, the data was compared with dynamic viscoelasticity measurements obtained from cantilever beam vibration tests performed on specimens cut from the sample panels. EXPERIMENTAL Theoretical Basis The dynamic viscoelasticity ( E * ) of the full-size WCP was determined using Eq. 1, * ' " E E iE (1) where E ’ is the storage modulus and E ” is the loss modulus. “Free-free” support refers to the panel being supported on its two nodal lines, which are located at 22.4% and 77.6% of its length. A panel’s free vibration under this support state is called “free-free” support vibration (Guan et al . 2015). Both calculated modal analysis and experimental modal analysis show that the first vibration mode of a full-size panel under this support state is the first-order bending along the length direction of the panel, which is the same as the vibration mode of a beam supported at the same locations (Guan et al . 2014; Zhou et al. 2014a). Therefore, the related equation for storage modulus and loss modulus of the beam in this support state can be used to derive the equation for storage modulus, Eq. 2, and loss modulus, Eq. 3, of the panel (Guo and Liu 1985) . The derived E ’ and E ” correspond to the storage modulus and loss modulus along the length direction of the panel, respectively,
ª
º
2
2 · « ¨ ' » ¸ ¨ ¸ « » © ' ¹ ¬ ¼ 2 π π 1 §
(2)
' E E
d
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Guan et al . (2016). “Dynamic viscoelasticity,” B io R esources 11(2), 4593-4604.
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