Authors: Tian Zhang ShuLin Bai Sandrine Bardet Tancrède Alméras Bernard Thibaut Jacques Beauchêne
Publish Date: 2011/10/01
Volume: 57, Issue: 5, Pages: 377-386
Abstract
The radial trends of vibrational properties represented by the specific dynamic modulus E′/ρ and damping coefficient tan δ were investigated for three tropical rainforest hardwood species Simarouba amara Carapa procera and Symphonia globulifera using freefree flexural vibration tests The microfibril angle MFA was estimated using Xray diffraction Consistent patterns of radial variations were observed for all studied properties E′/ρ was found to decrease from pith to bark which was strongly related to the increasing pithbark trend of MFA The variation of tan δ along the radius could be partly explained by MFA and partly by the gradient of extractives due to heartwood formation The coupling effect of MFA and extractives could be separated through analysis of the logtan δ versus logE′/ρ diagram For the species studied the extractive content putatively associated with heartwood formation generally tends to decrease the wood damping coefficient However this weakening effect of extractives was not observed for the inner part of the heartwood suggesting that the mechanical action of extractives was reduced during their chemical ageing
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