scholarly journals Effects of Grain Pattern on the Rolling Shear Properties of Wood in Cross-Laminated Timber

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 668
Author(s):  
Guofang Wu ◽  
Yong Zhong ◽  
Haiqing Ren
Keyword(s):  
Shear Modulus ◽  
Mechanical Performance ◽  
Wood Products ◽  
Rolling Shear ◽  
Shear Moduli ◽  
Factors Affecting ◽  
Cross Laminated Timber ◽  
Aspect Ratios ◽  
Shear Property ◽  
Pure Rolling

Rolling shear modulus and strength are the key factors affecting the mechanical performance of some wood products such as cross-laminated timber (CLT). As reported, rolling shear property strongly depends on the sawing pattern such as the aspect ratio and grain direction (grain mode). However, the mechanism behind this phenomenon has not yet been clarified. In this work, the rolling shear modulus and strength of spruce-pine-fir (SPF) with different grain modes and aspect ratios were experimentally investigated. In addition, a theoretical investigation was carried out to reveal the mechanism behind this phenomenon. The results exhibited that the rolling shear moduli of 0° and 90° grain-mode wood were the same. This value can be called the pure rolling shear modulus. Rolling shear modulus of wood with angles other than 0° and 90° can be calculated from the pure rolling shear modulus and grain angle. Therefore, this modulus can be called the apparent rolling shear modulus. Thus, using 0° and 90° grain-mode specimens to determine the pure rolling shear modulus and strength of wood is recommended.

scholarly journals Comparison of Theoretical and Laboratory Out-of-Plane Shear Stiffness Values of Cross Laminated Timber Panels

Buildings ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 146 ◽  
Author(s):  
Jan Niederwestberg ◽  
Jianhui Zhou ◽  
Ying-Hei Chui
Keyword(s):  
Shear Modulus ◽  
Cross Section ◽  
Single Layer ◽  
Beam Theory ◽  
Shear Stiffness ◽  
Plane Shear ◽  
Shear Moduli ◽  
Cross Laminated Timber ◽  
Highly Sensitive ◽  
Out Of Plane

The lay-up of cross laminated timber (CLT) leads to significant differences in properties over its cross-section. Particularly the out-of-plane shear behavior of CLT is affected by the changes in shear moduli over the cross-section. Results from laboratory shear tests are used to evaluate the shear stiffness of 3- and 5-layer CLT panels in their major and minor strength direction. The results are compared to calculated shear stiffness values on evaluated single-layer properties as well as commonly used property ratios using the Timoshenko beam theory and the shear analogy method. Differences between the two calculation approaches are pointed out. The shear stiffness is highly sensitive to the ratio of the shear modulus parallel to the grain to the shear modulus perpendicular to the grain. The stiffness values determined from two test measurements are compared with the calculated results. The level of agreement is dependent on the number of layers in CLT and the property axis of the CLT panels.

scholarly journals Elastic Mechanical Properties of 45S5-Based Bioactive Glass–Ceramic Scaffolds

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3244 ◽  
Author(s):  
Francesco Baino ◽  
Elisa Fiume
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Shear Modulus ◽  
Glass Ceramic ◽  
Poisson’S Ratio ◽  
Mechanical Performance ◽  
Poisson's Ratio ◽  
Shear Moduli ◽  
Bioactive Scaffolds

Porosity is recognized to play a key role in dictating the functional properties of bioactive scaffolds, especially the mechanical performance of the material. The mechanical suitability of brittle ceramic and glass scaffolds for bone tissue engineering applications is usually evaluated on the basis of the compressive strength alone, which is relatively easy to assess. This work aims to investigate the porosity dependence of the elastic properties of silicate scaffolds based on the 45S5 composition. Highly porous glass–ceramic foams were fabricated by the sponge replica method and their elastic modulus, shear modulus, and Poisson’s ratio were experimentally determined by the impulse excitation technique; furthermore, the failure strength was quantified by compressive tests. As the total fractional porosity increased from 0.52 to 0.86, the elastic and shear moduli decreased from 16.5 to 1.2 GPa and from 6.5 to 0.43 GPa, respectively; the compressive strength was also found to decrease from 3.4 to 0.58 MPa, whereas the Poisson’s ratio increased from 0.2692 to 0.3953. The porosity dependences of elastic modulus, shear modulus and compressive strength obeys power-law models, whereas the relationship between Poisson’s ratio and porosity can be described by a linear approximation. These relations can be useful to optimize the design and fabrication of porous biomaterials as well as to predict the mechanical properties of the scaffolds.

scholarly journals Comparison of Theoretical and Laboratory Out-of-Plane Shear Stiffness Values of Cross Laminated Timber Panels

2018 ◽  
Author(s):  
Jan Niederwestberg ◽  
Jianhui Zhou ◽  
Ying-Hei Chui
Keyword(s):  
Shear Modulus ◽  
Cross Section ◽  
Single Layer ◽  
Beam Theory ◽  
Shear Stiffness ◽  
Plane Shear ◽  
Shear Moduli ◽  
Cross Laminated Timber ◽  
Highly Sensitive ◽  
Out Of Plane

The lay-up of cross laminated timber (CLT) leads to significant differences in properties over its cross-section. Particularly the out-of-plane shear behavior of CLT is effected by the changes in shear moduli over the cross-section. Results from laboratory shear tests are used to evaluate the shear stiffness of 3- and 5-layer CLT panels in their major and minor strength direction. The results are compared to calculated shear stiffness values on evaluated single-layer properties as well as commonly used property ratios using the Timoshenko beam theory and the shear analogy method. Differences between the two calculation approaches are pointed out. The shear stiffness is highly sensitive to the ratio of the shear modulus parallel to the grain to the shear modulus perpendicular to the grain. The stiffness values determined from two test measurements are compared with the calculated results. The level of agreement is dependent on the number of layers in CLT and the property axis of the CLT panels.

The effect of edge gaps on shear strength and rolling shear modulus of cross laminated timber panels

2020 ◽  
Vol 259 ◽  
pp. 119710
Author(s):  
Charles Gardner ◽  
William G. Davids ◽  
Roberto Lopez-Anido ◽  
Benjamin Herzog ◽  
Russell Edgar ◽  
...  
Keyword(s):  
Shear Strength ◽  
Shear Modulus ◽  
Rolling Shear ◽  
Cross Laminated Timber

scholarly journals Performance evaluation of a novel cross-laminated timber made from flattened bamboo and wood lumber

BioResources ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. 5187-5202
Author(s):  
Peixing Wei ◽  
Brad Jianhe Wang ◽  
Hao Li ◽  
Libin Wang ◽  
Yingchun Gong ◽  
...  
Keyword(s):  
Carrying Capacity ◽  
Shear Failure ◽  
Mechanical Performance ◽  
Compression Modulus ◽  
Load Carrying Capacity ◽  
Wood Composite ◽  
Rolling Shear ◽  
Cross Laminated Timber ◽  
Load Carrying ◽  
And Control

A novel flattened bamboo-wood composite cross-laminated timber (CCLT) made from flattened bamboo and hemlock lumber was developed, and its mechanical performance was investigated and quantified in this work. The results demonstrated that the CCLT columns and control hemlock CLT counterparts had nearly equal axial compression strength, but the CCLT yielded a higher compression modulus of elasticity (MOE). Additionally, the CCLT compression behaviors were not significantly affected by the height. Compared with hemlock CLT, the CCLT exhibited a slightly higher flatwise bending MOE and strength in the major strength direction. Furthermore, the MOE and strength of the CCLT under edgewise bending were 17.3% less and 16.2% greater than those under flatwise bending, respectively. The load-carrying capacity of the CCLT was mainly governed by the interfacial failure between the bamboo and wood, in which no rolling shear failure was observed. Those features are unique for the new CCLT for engineered applications.

scholarly journals Evaluating Timoshenko Method for Analyzing CLT under Out-of-Plane Loading

Buildings ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 184
Author(s):  
MD Tanvir Rahman ◽  
Mahmud Ashraf ◽  
Kazem Ghabraie ◽  
Mahbube Subhani
Keyword(s):  
Shear Modulus ◽  
Shear Deformation ◽  
Numerical Study ◽  
Wood Products ◽  
Tangential Plane ◽  
Rolling Shear ◽  
Laminated Veneer Lumber ◽  
Engineered Wood ◽  
Out Of Plane ◽  
Cross Layers

Cross-laminated timber (CLT) is an engineered wood product made up of layers of structurally graded timber, where subsequent layers are oriented orthogonally to each other. In CLT, the layers oriented in transverse direction, generally termed as cross-layer, are subjected to shear in radial–tangential plane, which is commonly known as rolling shear. As the shear modulus of cross-layers is significantly lower than that in other planes, CLT exhibits higher shear deformation under out-of-plane loading in contrast to other engineered wood products such as laminated veneer lumber (LVL) and glue laminated timber (GLT). Several analytical methods such as Timoshenko, modified gamma and shear analogy methods were proposed to account for this excessive shear deformation in CLT. This paper focuses on the effectiveness of Timoshenko method in hybrid CLT, in which hardwood cross-layers are used due to their higher rolling shear modulus. A comprehensive numerical study was conducted and obtained results were carefully analyzed for a range of hybrid combinations. It was observed that Timoshenko method could not accurately predict the shear response of CLTs with hardwood cross layers. Comprehensive parametric analysis was conducted to generate reliable numerical results, which were subsequently used to propose modified design equations for hybrid CLTs.

Sign in / Sign up

Export Citation Format

Share Document