同等級柳杉集成元製造集成樑之力學性能

Abstract

本研究以抗彎試驗及非破壞性檢測技術超音波法、打音法測得柳杉（Cryptomeria japonica）集成元之抗彎彈性模數（Modulus of elasticity, MOE）與動彈性模數（Dynamic modulus of elasticity, DMOE），並評估其相關性。結果顯示，DMOE皆與MOE值成正相關性，其中，超音波DMOE（DMOEu）與MOE之R2值為0.92；打音DMOE（DMOEt）與MOE之R2為0.98。此外MOE、DMOEu及DMOEt三者數值呈現DMOEu>DMOEt>MOE之趨勢。顯示超音波法與打音法可用於評估集成元之MOE。將集成元之MOE依據中華民國國家標準CNS 11031（2016）進行等級區分，配置成同等級集成材，利用集成理論公式預測集成材之MOE。本研究利用該推算式所得之預測MOE分別為Eb與Eb’，Eb為未帶入膠合層之預測結果；Eb’為帶入膠合層之預測結果。結果顯示，Eb與Eb’皆較實際MOE大。此外，由於膠合層厚度於集成材厚度占有比例不大，因此可以忽視膠合層進行MOE預測。另以柳杉無節材製成與同等級集成材尺寸相同之實木試材，以抗彎試驗、超音波法、打音法測得MOE與DMOE，探討集成材與實木之DMOE與MOE相關性。結果顯示，集成材與實木兩者之DMOE皆與MOE呈正相關性，DMOEu與MOE以及DMOEt與MOE之R2值於實木分別為0.93與0.95；於集成材分別為0.94與0.96。顯示超音波法與打音法可用於評估集成材與實木之MOE。針對相同尺寸與相同機械等級之集成材與實木試材，比較兩者抗彎強度（Modulus of rupture, MOR）及剪斷模數（Shear modulus, G）之差異。結果顯示，兩者之 MOR與G皆無顯著差異，推斷集成材與實木試材於相同尺寸與相同機械等級狀態下，集成材之膠合層不影響其MOR與G。綜合以上所述，非破壞性檢測技術可用於評估柳杉製材品（實木、集成材）之MOE，且透過集成元等級區分、配置與設計，可使集成材力學性質相當於實木試材之學性質，進而提升原木利用率。

Firstly, this study investigated the modulus of elasticity (MOE) and dynamic modulus of elasticity (DMOE) of Cryptomeria japonica laminae using static bending test and nondestructive testing (NDT) techniques, including ultrasonic wave method and tap tone method. The correlation between MOE and DMOE was evaluated. The results showed a positive correlation between DMOE and MOE, the coefficients of determination (R²) between DMOEu (DMOE from ultrasonic wave method) and MOE being 0.92, and between DMOEt (DMOE from tap tone method) and MOE being 0.98. Furthermore, the values of MOE, DMOEu and DMOEt have the trend of DMOEu > DMOEt > MOE. It shows that both ultrasonic wave method and tap tone method are effective for evaluating the MOE of laminae. Secondly, The MOE values of laminae were graded according to the National Standards of the Republic of China, CNS 11031 (2016). Then assembled into Homogeneous-grade glulam. Predicting MOE of the glulam were predicted by formula, with Eb representing the value excluding the glue layer and Eb' representing the value including the glue layer. The results showed that both Eb and Eb' overestimated the actual MOE. Additionally, the effect of the glue layer was considered negligible due to its relatively small proportion of the total glulam thickness. Thirdly, solid wood specimens with the same dimensions and mechanical grade as glulam, were fabricated from Cryptomeria japonica for comparison. The MOE and DMOE were measured using static bending test, ultrasonic wave method, and tap tone method to evaluate the correlations between MOE and DMOE in glulam and solid wood. The results showed MOE and DMOE of glulam and solid wood have a positive correlation. The R2 between DMOEu and MOE of solid wood is 0.93, the R2 between DMOEt and MOE of solid wood is 0.95; the R2 between DMOEu and MOE of glulam is 0.94, the R2 between DMOEt and MOE of glulam is 0.96. It shows that the NDT can be used to evaluate MOE of solid wood and glulam. Furthermore, glulam and solid wood specimens with identical dimensions and mechanical grades were compared to examine differences in their modulus of rupture (MOR) and shear modulus (G), both obtained from static bending tests. The results indicated no significant differences in either MOR or G between glulam and solid wood , suggesting that the presence of glue layers does not affect these properties under equivalent conditions. It leads to the conclusion that, NDT can be used to evaluate the MOE of wood products of japonica (solid wood and glulam). Glulam mechanical properties can be similar to solid wood by design, and glulam can improve the utilization rate of wood.