This is the third and final paper in a three-part series investigating the effect of location wit... more This is the third and final paper in a three-part series investigating the effect of location within a tree on the mechanical properties of individual wood tracheids. This paper focuses on the definition of juvenile, transition, and mature zones as classified by fiber stiffness, strength, microfibril angle, and cross-sectional area. The average modulus of elasticity and ultimate tensile stress of all loblolly pine fibers were, in equal proportion of earlywood and latewood, 17.3 Gpa and 824 Mpa, respectively. The average microfibril angle was found to be 15.4 degrees, with rings 5 and 48 averaging 26.8 and 6.1 degrees, respectively. Normalization of all mechanical and physical properties showed that the juvenile zone is not cylindrical but rather biconical, tapering from stump to below the live crown and then again from the live crown to the bole tip. The transition zone parallels the juvenile zone, ranging in width from 3 to 15 rings. Fiber properties continued to improve slightly t...
This is the third and final paper in a three-part series investigating the effect of location wit... more This is the third and final paper in a three-part series investigating the effect of location within a tree on the mechanical properties of individual wood tracheids. This paper focuses on the definition of juvenile, transition, and mature zones as classified by fiber stiffness, strength, microfibril angle, and cross-sectional area. The average modulus of elasticity and ultimate tensile stress of all loblolly pine fibers were, in equal proportion of earlywood and latewood' 17.3 Gpa and 824 Mpa, respectively. The average microfibril angle was found to be 15.4 degrees, with rings 5 and 48 averaging 26.8 and 6.1 degrees, respectively. Normalization of all mechanical and physical properties showed that the juvenile zone is not cylindrical but rather biconical, tapering from stump to below the live crown and then again from the live crown to the bole tip. The transition zone parallels the juvenile zone, ranging in width from 3 to 15 rings. Fiber properties continued to improve slight...
Ordinary Portland cement (OPC) clinker mainly consist four minerals, tricalcium silicate (C3S), d... more Ordinary Portland cement (OPC) clinker mainly consist four minerals, tricalcium silicate (C3S), dicalcium silicate (C2S,), tricalcium aluminate (C3A), and tetracalcium aluminoferrite (C4AF). To learn the doping behaviors of Zn in OPC clinker, a series of samples were prepared by calcinating the mixtures of CaCO3, SiO2, Al2O3, Fe2O3, and ZnO. Our results from energy-dispersive spectroscopy, X-ray diffraction and density functional theoretical simulations show that a small amount of ZnO enter C3S and C2S by replacing Ca ions while most incorporate into C4AF by substituting Fe atoms, resulting in a decrease of C3A in OPC as dosage increases. Further analyses from partial density of states and distributions of bond order-bond length indicate that the doping preference can be ascribed to the similar electron contributions and small structure distortions between host and guest ions. Unlike the strong Fe‒O bond, the newly formed Zn‒O is much weaker. The weak Zn‒O may be responsible for the limited solubility of Zn in C4AF. These results provide a possibility of increasing solubility of Zn in OPC clinker by increasing the contents of C3A and C4AF, thus will be very meaningful in the synthesis of OPC clinker by utilizing Zn-bearing alternative raw materials.
In this work, the usability of the Burger body model (BBM) for determining the behavior of orient... more In this work, the usability of the Burger body model (BBM) for determining the behavior of oriented strand boards (OSBs) under long-term loads was evaluated. The actual bending strain data and predicted strain data as a function of different stress levels and load durations under constant environmental conditions (25 ± 2°C and 50% relative humidity) were compared. Two test groups, short-term bending tests and long-term creep-rupture bending tests, were performed according to relevant ASTM standards. Specimens were randomly assigned to three groups and loaded at 47% (132.2 kg), 51% (137.4 kg), or 55% (154.9 kg) of the mean static short-term flexural strength. Specimen creep was monitored for 10,000 h using an automated measurement system. The four-parameter BBM parameters were obtained for all specimens at 2000-h time intervals, providing five different estimates. Measured strain values were compared with strain predictions from the BBM and with the goal of evaluating length of exper...
Abstract The effect of gaps between boards in transverse layers of cross-laminated timber (CLT) o... more Abstract The effect of gaps between boards in transverse layers of cross-laminated timber (CLT) on shear strength was investigated. Five-ply specimens with gaps of 0, 6, 89 and 178 mm were subjected to short-span three-point bending tests. Digital imaging correlation (DIC) was used to quantify strains and displacements in core layers. Panel shear capacity met the requirements of the PRG 320 standard for performance-rated CLT for the gap sizes tested, suggesting that small gaps do not reduce shear strength enough to warrant consideration in design. DIC data and Timoshenko beam theory were used to estimate rolling shear modulus and specimen deflections, which agreed well with measured values.
Single fiber fracture is important in understanding the fundamental failure mechanisms in wood/po... more Single fiber fracture is important in understanding the fundamental failure mechanisms in wood/polymer composite products such as medium density fiberboard (MDF). The mechanical properties and fracture behavior of individual wood fibers has only recently been observable using a combination of environmental scanning electron microscopy (ESEM), laser scanning confocal microscopy and digital image correlation (DIC). Previous work has shown that specific areas on the fiber such as microcompressions and pits acted as crack nucelators and induce a brash fracture across the surface of the fiber. Given the development of these procedures it is now possible to observe and measure the mechanical properties and fracture characteristics of the wood fiber/ polymer composite fibers.Individual black spruce wood fibers were coated with diphenylmethane 4-4'diisocyanate resin containing Hostasol Red GG. The addition of the Hostasol Red flurochrome provided the option of quantifying resin coverage...
Abstract The bending and shear performance of hybrid cross-laminated timber (CLT) panels made fro... more Abstract The bending and shear performance of hybrid cross-laminated timber (CLT) panels made from Spruce-Pine-Fir (South) (SPFs) and laminated strand lumber (LSL) are examined. Four configurations of three-layer CLT were fabricated: all-SPFs control specimens, all-LSL specimens, hybrid specimens with SPFs faces and an LSL core, and hybrid specimens with LSL faces and an SPFs core. Bending tests were conducted to assess flexural strength and stiffness. Additionally, three-point bending tests were performed to assess shear performance. The incorporation of LSL in the core of CLT panels increased mean panel bending stress at failure by 23% through mitigation of rolling shear failure.
Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indi... more Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.
Tracheid microfibril angle (MF-angle) of dominant and codominant red pine (Pinus resinosa Ait.) w... more Tracheid microfibril angle (MF-angle) of dominant and codominant red pine (Pinus resinosa Ait.) was studied through age 20 in a 57-year-old plantation and in a 42-year-old natural stand in eastern Maine. In the plantation, mean ring MF-angle decreased with age from 30 degrees at age 2 to 15 degrees at age 20. In the natural stand MF-angle decreased from 30 degrees at age 2 to 18 degrees at age 20. In both stands, MF-angle decreased from earlywood to latewood, and the difference between earlywood and latewood MF-angle increased with age. The correlation between both the flexural strength and stiffness of juvenile wood and MF-angle was negative, with bending MOE more sensitive than flexural strength. Both properties were positively correlated to specific gravity. The results suggest that cultural practices that increase ring width early in stand development may increase MF-angle and reduce modulus of rupture and modulus of elasticity.
This is the third and final paper in a three-part series investigating the effect of location wit... more This is the third and final paper in a three-part series investigating the effect of location within a tree on the mechanical properties of individual wood tracheids. This paper focuses on the definition of juvenile, transition, and mature zones as classified by fiber stiffness, strength, microfibril angle, and cross-sectional area. The average modulus of elasticity and ultimate tensile stress of all loblolly pine fibers were, in equal proportion of earlywood and latewood, 17.3 Gpa and 824 Mpa, respectively. The average microfibril angle was found to be 15.4 degrees, with rings 5 and 48 averaging 26.8 and 6.1 degrees, respectively. Normalization of all mechanical and physical properties showed that the juvenile zone is not cylindrical but rather biconical, tapering from stump to below the live crown and then again from the live crown to the bole tip. The transition zone parallels the juvenile zone, ranging in width from 3 to 15 rings. Fiber properties continued to improve slightly t...
This is the third and final paper in a three-part series investigating the effect of location wit... more This is the third and final paper in a three-part series investigating the effect of location within a tree on the mechanical properties of individual wood tracheids. This paper focuses on the definition of juvenile, transition, and mature zones as classified by fiber stiffness, strength, microfibril angle, and cross-sectional area. The average modulus of elasticity and ultimate tensile stress of all loblolly pine fibers were, in equal proportion of earlywood and latewood' 17.3 Gpa and 824 Mpa, respectively. The average microfibril angle was found to be 15.4 degrees, with rings 5 and 48 averaging 26.8 and 6.1 degrees, respectively. Normalization of all mechanical and physical properties showed that the juvenile zone is not cylindrical but rather biconical, tapering from stump to below the live crown and then again from the live crown to the bole tip. The transition zone parallels the juvenile zone, ranging in width from 3 to 15 rings. Fiber properties continued to improve slight...
Ordinary Portland cement (OPC) clinker mainly consist four minerals, tricalcium silicate (C3S), d... more Ordinary Portland cement (OPC) clinker mainly consist four minerals, tricalcium silicate (C3S), dicalcium silicate (C2S,), tricalcium aluminate (C3A), and tetracalcium aluminoferrite (C4AF). To learn the doping behaviors of Zn in OPC clinker, a series of samples were prepared by calcinating the mixtures of CaCO3, SiO2, Al2O3, Fe2O3, and ZnO. Our results from energy-dispersive spectroscopy, X-ray diffraction and density functional theoretical simulations show that a small amount of ZnO enter C3S and C2S by replacing Ca ions while most incorporate into C4AF by substituting Fe atoms, resulting in a decrease of C3A in OPC as dosage increases. Further analyses from partial density of states and distributions of bond order-bond length indicate that the doping preference can be ascribed to the similar electron contributions and small structure distortions between host and guest ions. Unlike the strong Fe‒O bond, the newly formed Zn‒O is much weaker. The weak Zn‒O may be responsible for the limited solubility of Zn in C4AF. These results provide a possibility of increasing solubility of Zn in OPC clinker by increasing the contents of C3A and C4AF, thus will be very meaningful in the synthesis of OPC clinker by utilizing Zn-bearing alternative raw materials.
In this work, the usability of the Burger body model (BBM) for determining the behavior of orient... more In this work, the usability of the Burger body model (BBM) for determining the behavior of oriented strand boards (OSBs) under long-term loads was evaluated. The actual bending strain data and predicted strain data as a function of different stress levels and load durations under constant environmental conditions (25 ± 2°C and 50% relative humidity) were compared. Two test groups, short-term bending tests and long-term creep-rupture bending tests, were performed according to relevant ASTM standards. Specimens were randomly assigned to three groups and loaded at 47% (132.2 kg), 51% (137.4 kg), or 55% (154.9 kg) of the mean static short-term flexural strength. Specimen creep was monitored for 10,000 h using an automated measurement system. The four-parameter BBM parameters were obtained for all specimens at 2000-h time intervals, providing five different estimates. Measured strain values were compared with strain predictions from the BBM and with the goal of evaluating length of exper...
Abstract The effect of gaps between boards in transverse layers of cross-laminated timber (CLT) o... more Abstract The effect of gaps between boards in transverse layers of cross-laminated timber (CLT) on shear strength was investigated. Five-ply specimens with gaps of 0, 6, 89 and 178 mm were subjected to short-span three-point bending tests. Digital imaging correlation (DIC) was used to quantify strains and displacements in core layers. Panel shear capacity met the requirements of the PRG 320 standard for performance-rated CLT for the gap sizes tested, suggesting that small gaps do not reduce shear strength enough to warrant consideration in design. DIC data and Timoshenko beam theory were used to estimate rolling shear modulus and specimen deflections, which agreed well with measured values.
Single fiber fracture is important in understanding the fundamental failure mechanisms in wood/po... more Single fiber fracture is important in understanding the fundamental failure mechanisms in wood/polymer composite products such as medium density fiberboard (MDF). The mechanical properties and fracture behavior of individual wood fibers has only recently been observable using a combination of environmental scanning electron microscopy (ESEM), laser scanning confocal microscopy and digital image correlation (DIC). Previous work has shown that specific areas on the fiber such as microcompressions and pits acted as crack nucelators and induce a brash fracture across the surface of the fiber. Given the development of these procedures it is now possible to observe and measure the mechanical properties and fracture characteristics of the wood fiber/ polymer composite fibers.Individual black spruce wood fibers were coated with diphenylmethane 4-4'diisocyanate resin containing Hostasol Red GG. The addition of the Hostasol Red flurochrome provided the option of quantifying resin coverage...
Abstract The bending and shear performance of hybrid cross-laminated timber (CLT) panels made fro... more Abstract The bending and shear performance of hybrid cross-laminated timber (CLT) panels made from Spruce-Pine-Fir (South) (SPFs) and laminated strand lumber (LSL) are examined. Four configurations of three-layer CLT were fabricated: all-SPFs control specimens, all-LSL specimens, hybrid specimens with SPFs faces and an LSL core, and hybrid specimens with LSL faces and an SPFs core. Bending tests were conducted to assess flexural strength and stiffness. Additionally, three-point bending tests were performed to assess shear performance. The incorporation of LSL in the core of CLT panels increased mean panel bending stress at failure by 23% through mitigation of rolling shear failure.
Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indi... more Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.
Tracheid microfibril angle (MF-angle) of dominant and codominant red pine (Pinus resinosa Ait.) w... more Tracheid microfibril angle (MF-angle) of dominant and codominant red pine (Pinus resinosa Ait.) was studied through age 20 in a 57-year-old plantation and in a 42-year-old natural stand in eastern Maine. In the plantation, mean ring MF-angle decreased with age from 30 degrees at age 2 to 15 degrees at age 20. In the natural stand MF-angle decreased from 30 degrees at age 2 to 18 degrees at age 20. In both stands, MF-angle decreased from earlywood to latewood, and the difference between earlywood and latewood MF-angle increased with age. The correlation between both the flexural strength and stiffness of juvenile wood and MF-angle was negative, with bending MOE more sensitive than flexural strength. Both properties were positively correlated to specific gravity. The results suggest that cultural practices that increase ring width early in stand development may increase MF-angle and reduce modulus of rupture and modulus of elasticity.
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Papers by Stephen Shaler