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Experimental tests of cross-laminated timber (CLT)-concrete composite floor panels were conducted. The tests consisted of linear-elastic tests of square CLT-concrete composite panels with a novel shear connector to determine elastic orthotropic plate properties. After the linear-elastic tests, the panels were subjected to a patch load at the center of the panel and tested to failure. To investigate load transfer across longitudinal joints between adjacent panels, nonuniform bending tests were conducted. Results from the experimentally measured orthotropic plate properties showed that the shear connector increased the bending stiffness in the weak direction of the panel compared to prior test results using conventional shear connectors. The tests to failure exhibited larger differences in behavior between the strong and weak orientations of the specimens, with both showing substantial inelastic behavior prior to failure. Numerical finite element models of the patch-load test showed good agreement with experimental results. Analytical formulas using the obtained orthotropic plate properties did not agree with experimental results for the patch-load at linear scales, suggesting the simplified method is currently not suited for CLT-concrete two-way bending. Load-transfer tests found that the reinforced concrete topping is capable of transferring load across the longitudinal joint of two parallel panels to enable two-way bending of composite timber–concrete floors and that the addition of a plywood spline with closely spaced screws enables a higher degree of force transfer. [ABSTRACT FROM AUTHOR]

The main objective of this work is to characterize the stress–strain relationship of cross-laminated timber (CLT) wall panels when loaded in compression and how different confinement mechanisms provide compression reinforcement for the CLT panels. CLT crushing tests were performed to define the behavior of CLT under compression up to the failure point, defined here as the strain at which the gross stress falls by 20% from the peak value. Testing included monotonic uniform compression experiments of five-ply CLT with specimens that were 0.457 m wide by 1.52 m long. The motion of the specimens perpendicular to loading direction was restrained at midlength to prevent buckling. Twelve specimens were tested, including six bare CLT specimens and six reinforced specimens of CLT—three with self-tapping screws while the other three with self-tapping screws and an additional U-shape steel plate at the bottom of the specimens. Various damage points were observed during the tests, including (1) point at the onset of damage (through visual observation and instrumental observation) (2) point of initiation of strength degradation, (3) point at which buckling occurs, (4) point at which 25.4 mm delamination was observed, and (5) failure point. Three axial compression stress–strain models were adopted, calibrated, and compared. Results indicate that a stress–strain model combining linear and cubic functions for the elastic and softening responses, respectively, captures well the CLT inelastic behavior under compression. [ABSTRACT FROM AUTHOR]

Connections play a vital role in the transfer of lateral forces and energy dissipation in cross-laminated timber (CLT) structural systems. However, moisture exposure (e.g., rain during or after construction) can affect the durability of CLT structural members and their connections due to the hygroscopic nature of wood. Limited knowledge exists on the moisture performance of CLT connections. Therefore, in this study, a CLT shear wall-to-diaphragm angle bracket connection was exposed to simulated rain and relative humidity cycling (wetting) and subsequent redrying followed by mechanical loading cyclic testing. Four wood species (Douglas-fir, southern pine, Norway spruce, and spruce-pine-fir) and three wetting durations were applied to understand the effect of moisture intrusion on the connection performance, which was evaluated in terms of strength, stiffness, and energy dissipation. Two force–displacement backbone models were fitted to the experimental data. The results suggest a statistically significant increase (9%–15% for different species) in the peak strength and no change in the stiffness and energy dissipation capacity after the wetting and redrying cycles. However, additional studies should be conducted to gain further insight into the observed increase in load-carrying capacity. Additionally, the authors caution against considering any strength increase until further studies are conducted. [ABSTRACT FROM AUTHOR]

Wood-based composites (WBCs) are engineered wood products that are commonly used in the building and furniture industries. Most research on their durability has relied on internal bond testing, bending strength properties, or damage observations. An alternative property with potentially more information is fracture toughness. Here, fracture toughness was continuously measured during crack propagation for three different composites—oriented strand board (OSB), medium density fiberboard (MDF), and particleboard (PB). The resulting plots for fracture toughness as a function of crack growth are known as the material's R curve. To assess the role of temperature on WBC durability, R curve experiments were repeated at 10 different temperatures from 20 to 200 °C. Trends in experimental results could be described by a trilinear model. OSB and MDF toughness initially increased with temperature and then decreased above 80 °C. The toughness of PB, which was made with a different resin, remained constant or decreased slightly until decreasing faster above 140 °C. Both the resin type and composite structure affected the results. [ABSTRACT FROM AUTHOR]

Cross-laminated timber (CLT) is an engineered wood product offering several advantages for wood utilization in midrise and tall buildings. However, moisture intrusion poses significant risks since it can affect the durability of CLT structural members and their connections. There has been much research on connection performance to understand their seismic response. However, the impact of moisture on the performance of CLT connectors is less understood. Cyclic tests were conducted on a series of CLT shear wall-to-diaphragm L-bracket (angle bracket) connections after subjecting them to a wetting and redrying cycle. The study includes three exposure durations and four wood species (Douglas fir, Southern yellow pine, Norway spruce, and spruce-pine-fir) to investigate the effect of moisture exposure on the connection performance. The performance was characterized in terms of strength, stiffness, and energy dissipation. In addition, two existing engineering force-displacement models were fitted to the experimental data. Results indicate that the changes due to wetting and redrying cycling were not statistically significant for the load-carrying capacity and stiffness. In contrast, a statistically significant decrease in the total energy dissipation capacity was observed. [ABSTRACT FROM AUTHOR]

With the rapidly growing interest in using structural timber, a need exists to inspect and assess these structures using non-destructive testing (NDT). This review article summarizes NDT methods for wood inspection. After an overview of the most important NDT methods currently used, a detailed review of Ground Penetrating Radar (GPR) and Ultrasonic Testing (UST) is presented. These two techniques can be applied in situ and produce useful visual representations for quantitative assessments and damage detection. With its commercial availability and portability, GPR can help rapidly identify critical features such as moisture, voids, and metal connectors in wood structures. UST, which effectively detects deep cracks, delaminations, and variations in ultrasonic wave velocity related to moisture content, complements GPR's capabilities. The non-destructive nature of both techniques preserves the structural integrity of timber, enabling thorough assessments without compromising integrity and durability. Techniques such as the Synthetic Aperture Focusing Technique (SAFT) and Total Focusing Method (TFM) allow for reconstructing images that an inspector can readily interpret for quantitative assessment. The development of new sensors, instruments, and analysis techniques has continued to improve the application of GPR and UST on wood. However, due to the hon-homogeneous anisotropic properties of this complex material, challenges remain to quantify defects and characterize inclusions reliably and accurately. By integrating advanced imaging algorithms that consider the material's complex properties, combining measurements with simulations, and employing machine learning techniques, the implementation and application of GPR and UST imaging and damage detection for wood structures can be further advanced. [ABSTRACT FROM AUTHOR]

Connections in mass timber structural systems transfer lateral forces from mass timber elements such as shear walls to floor diaphragms. Cross-laminated timber (CLT) is a prominent engineered mass timber material used to manufacture walls and floor assemblies. Fire performance research of CLT walls and floors has been abundant in recent years in an effort to develop an understanding of the performance of structural members under fire. Some fire-protected structural elements, including connections, may not be directly exposed to flames in a fire event but will experience elevated temperatures. There is limited research on elevated temperature performance of CLT connections, and consequently a lack of understanding of their fire performance in CLT structures. To aid in bridging this knowledge gap, in this study a series of cyclic shear tests were conducted on a CLT wall-to-floor bracket connection assembly to characterize thermal degradation according to a matrix of 28 exposure duration–temperature combinations. Two different methods were employed to develop force-displacement backbone models from the experimental hysteresis data. Models from both methods indicate an overall degradation of the connection performance in terms of load carrying capacity, elastic stiffness, ductility, and energy dissipation with increasing exposure to elevated temperatures. [ABSTRACT FROM AUTHOR]

This research investigated the mechanical characteristics of cross-laminated timber (CLT) connections fastened with structural wood screws, also known as self-tapping screws (STS). The CLT connection assemblies were toe-screwed (TS) at 45° and cyclically tested in tension and in-plane shear to evaluate the failure modes and applicability as seismic connections in CLT shear walls. The connection assemblies were representative of full-scale CLT shear walls connected to CLT floors as often seen in platform construction. Toe-screwed CLT connections exhibited screw fracture, head pull-through, and pinched hysteresis loops. Mechanical connection properties and backbone curves were extracted for comparison with design estimates. A head pull-through design method was developed, which predicted peak strength within 5% of test results. Connection parameters for ASCE/SEI 41 idealized-component curves were presented for use in performance-based design nonlinear-static pushover analysis. Combining the presented ASCE/SEI 41 parameters with the proposed design method and test results provides a simple and reasonably accurate nonlinear toe-screwed connection response curve. Partially threaded washer-headed screws were found to be superior to fully threaded screws in seismic applications due to their 15 times greater ultimate deformation capacity, substantially greater energy dissipation, similar peak strength, and similar elastic stiffness. However, the yield strength of partially threaded STS was found to be 48% of the yield strength of fully threaded STS. [ABSTRACT FROM AUTHOR]

Connections in mass timber structural systems are critical for transferring lateral forces from mass timber elements such as shear walls and diaphragms. Cross-laminated timber (CLT) is a prominent mass timber material used to manufacture these wall and floor assemblies. Although research exists that investigated the fire performance of CLT walls and floors, very little investigation has been devoted to the thermal performance of the connection systems themselves. This void in the data and knowledge surrounding CLT connections is an impediment for modeling the elevated temperature performance of CLT structures. Therefore, a series of shear tests were conducted on a CLT L-bracket connection assembly to characterize the thermal degradation of peak loads and initial stiffness as a function of exposure duration at a given temperature. A total of 116 specimens, including four control specimens, were tested according to a matrix of 28 exposure duration-temperature combinations. Two analytical models are developed to explain the thermal degradation—one assuming a mechanism based on first-order kinetics and the second using a statistical regression. The results of this work indicate that the degradation of peak load and initial stiffness with respect to exposure duration occurred at a linear rate and depended on temperature, according to the Arrhenius activation energy theory. This research is a step toward a holistic evaluation of elevated temperature modeling of CLT structures. [ABSTRACT FROM AUTHOR]

While the use of cross-laminated timber (CLT) panels for building construction has increased over the last several decades, current standards and existing literature provide limited information regarding the design of CLT diaphragms or the prediction of their deflections when subjected to wind and strong earthquake motions. This paper presents the design and assessment of a CLT diaphragm that was part of a full-scale two-story structure subjected to shake-table testing. An analytical model is proposed for diaphragm deflection accounting for in-plane shear and bending stiffness, as well as the stiffness of various connections. Moreover, a refined numerical modeling strategy is proposed in order to consider phenomena such as panel-to-panel gap closure. Results indicate that the analytical model yields conservative results both in terms of deflections and forces when compared to the numerical model that simulates similar sources of strength and stiffness. The analytical model is suitable for the design of symmetric diaphragms with regular shapes, whereas the numerical model can also be used to model asymmetric diaphragms with irregular shapes. [ABSTRACT FROM AUTHOR]

Mass timber construction has seen a growing interest in North America and worldwide. In the US, code provisions allow mass timber buildings to be up to 82 m tall, but with floor slabs requiring a noncombustible, usually cementitious, topping over mass timber panels (MTPs). Designing the MTP and concrete topping to act compositely can increase the strength and stiffness compared to noncomposite MTP floors. Several connections are available to create composite action between an MTP and a concrete topping, with self-tapping screws being the most widely considered practice. A new test fixture and testing method were developed to characterize connection properties and facilitate the selection of fasteners most suitable for developing composite action. Three conventional self-tapping screws were experimentally investigated at the single-fastener scale. The screws were subjected to withdrawal at 90° and 45° orientations to the interface plane between the MTP and concrete. Withdrawal from both the MTP substrate and concrete topping was investigated. Three MTP materials were tested: cross-laminated timber (CLT) consisting of two different wood species and a mass ply panel (MPP). Results demonstrated that the pullout failure of the screwhead from the concrete was the limiting failure mode. Comparisons were made between the experimental results and analytical models for screw withdrawal to assess the applicability of available models to the different MTPs. These models underestimated the capacity of the tested fasteners for all samples except for the fully threaded screws. [ABSTRACT FROM AUTHOR]

The quality of wood composites is dependent on the bondlines' performance and their moisture resistance. The effect of moisture intrusion into bondlines is the focus of this study. The strain profile in the bondline during loading was investigated and the effects of weathering on the bondline were quantified by digital image correlation (DIC), while load deflection data were collected from lap-shear tests (LShTs). A total of 75 LShTs were evaluated including four different adhesive types with Douglas-fir wood, out of which 39 served as controls and 36 as substrates for weathering. The effect of weathering on failure load was not statistically significant. Only the bonded surface and adhesive type have significant effects on failure load, as well as the three-way interaction between the bonded surface, adhesive, and weathering, as revealed by three-way analysis of variance (ANOVA). The average effective shear moduli for the weathered samples were significantly lower than those for the control samples. [ABSTRACT FROM AUTHOR]

Synthesis of nano-crystalline hydroxyapatite (HAp) from fish scale ( Catla catla ) was carried out by calcining of raw fish scale between 200 °C and 1200 °C. The synthesized powders were characterized using thermogravimetry – differential thermal analysis (TGA-DTA), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, inductively coupled plasma atomic emission spectroscopy (ICP-AES), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The crystallinity, crystallite size, strain and cell parameters of fish scale derived calcined powders and chemically synthesized HAp (S-HAp) powders were estimated from XRD data. The average crystallite size of fish scale derived HAp powder increased with increasing calcination temperature. The fish scale derived HAp (FSH800) and S-HAp, calcined at 800 °C, showed crystallite size of 30 nm and 60 nm, respectively. ICP-AES analysis revealed that the fish scale derived HAp powder calcined at 1200 °C (FSH1200) contain significantly high amount of magnesium and strontium ions compared to S-HAp. After sintering at 1200 °C for 1 h, the relative density of FSH1200 was 20% higher than that of S-HAp due to better sinterability as a result of its small crystallite size and the presence of trace elements. In vitro cytotoxicity studies performed using human osteoblast-like cells (MG63) and mouse osteoblast cell line (MC3T3-E1) demonstrated that fish scale derived HAp (FSH1200) is non-toxic. [ABSTRACT FROM AUTHOR]

Green building practices have created an opportunity for the forest products industry to become a leader in the creation of in- novative building products derived from renewable materials. In other industries, sandwich composites have proven to be efficient structures by meeting structural demands of traditional panel products while consuming less material. A prototype molded-core sandwich panel made of span-rated oriented strand board (OSB) facings and a bidirectional molded wood-strand core was produced. Critical mechanical properties were evaluated to determine the feasibility of this product for use in building applications. The goals of this study were to generate details on structural performance of the product, validate the design, and provide suggestions for future product development. Results indicate that this molded-core panel performs particularly well in flexure while connection properties had the largest scope for improvement. Sufficient performance was observed to validate the design, warranting production and testing of panels sized for end-use. Future product development should explore different connection systems, perform detailed engineering analyses of the mechanical properties necessary for complete structural design, and characterize physical properties of the panel. [ABSTRACT FROM AUTHOR]

This study explored the suitability of fracture toughness properties for durability assessment of wood composite panels by observing changes in fracture toughness during crack propagation following cyclic exposure to moisture conditions. The main objective was to develop a new method for ranking the role of adhesives in the durability of wood-based composites. This new approach was compared to conventional mechanical performance tests, such as observing strength and stiffness loss after exposure. Comparing changes in fracture toughness as a function of crack length after moisture cycling shows that this approach can distinguish different adhesive systems on the basis of their durability, while conventional tests fail in this regard. The most and least durable adhesives (polyvinyl acetate and phenol formaldehyde) could be distinguished based on steady-state toughness alone, but this was not the case for the performance of two other adhesives (emulsion polymer isocyanate and phenol resorcinol formaldehyde). Further analysis of experimental R curves (toughness as a function of crack length) based on kinetics of degradation was able to rank all adhesives confidently. Probably, the failure of conventional tests in this context is that they are based on initiation of failure, while the fracture tests require consideration of fracture properties after a significant amount of crack propagation has occurred. [ABSTRACT FROM AUTHOR]

Limited research exists on the deformation compatibility behavior of mass timber beam-to-column connections. Therefore, to investigate this behavior, large-scale experimental monotonic testing was performed on five different glue-laminated (glulam) beam-to-column connections. The purpose of this research was to create a better fundamental understanding of the deformation compatibility behavior of mass timber beam-to-column connections. Three connections were custom-designed connections, and two were pre-engineered connections. Specimens included the presence of cross-laminated timber (CLT) decking on the beam, as well as combined lateral and gravity loading. Monotonic tests pushed specimens to a target story drift of 7.2% at a rate of 0.51 mm/s. The data were analyzed, and the yield force, yield displacement, initial stiffness, secant stiffness, and connection classification (categorized as either rigid, semirigid, or flexible) were calculated for each connection. Per the connection classification methodology used, all connections were classified as flexible (simple) connections. However, the pre-engineered connections use substantially more screws and plates thereby increasing the cost and effort of installation. The results demonstrate that in some cases simple custom connections can have a larger yield force and initial stiffness than pre-engineered connections, and due to the reduction in number of screws, there was less damage within the connection at the completion of the test. The forces required to push connections to 2% drift all exceeded the lateral force capacity of the connections; however, all connections maintained load-carrying capacity throughout testing. [ABSTRACT FROM AUTHOR]

New building code changes enable mass timber panels (MTP), including cross-laminated timber (CLT), to be used in moderate and tall buildings as a floor system, usually with a concrete topping. A floor system of CLT composite with a reinforced concrete topping slab can provide increased stiffness and strength, making the system more advantageous. Present connection methods used to produce composite action within timber-concrete composites (TCC) have limitations when considering constructability or performance. This study presents experimental results from four (4) shear connectors for CLT-concrete composite floor systems, including three developed for this study. The connectors included self-tapping screws (STS) at 45-degrees, a modified lag screw with an integral plate washer that bears on the CLT surface at installation, a steel angle anchored only at the end of the span, and an inverted-T steel section with stem perforations. Different tests were performed on the different connectors including individual fastener tests, push-off group tests, and full-scale one-way bending tests. The push-off group tests showed that the proposed washer-screw exhibited higher stiffness and strength than a conventional STS. The full-scale one-way bending testing showed that the STS specimen exhibited the lowest strength of the alternatives. The inverted-T section exhibited the highest stiffness, while the other three connections had similar stiffness to the STS. [ABSTRACT FROM AUTHOR]

To quantify the postpeak residual capacity and to gain insights into the load transfer mechanism of a shear wall, nail connection tests were performed on salvaged connections after a monotonic shear wall test loaded up to peak load. Experimental results reveal that there is a loss of strength in most of the fasteners studied, indicating that almost all the fasteners contribute toward racking resistance of the wall. The maximum loss of strength was observed for the fastener in the uplift corner and for the fastener along the middle stud. Another area where fasteners exhibited a significant loss of strength was in plate connection located at the bottom plate. The performance of a shear wall can be enhanced by strengthening the two areas - uplift corner and bottom plate. [ABSTRACT FROM AUTHOR]

The deformation compatibility behavior of glue-laminated (glulam) beam-to-column connections is not yet well understood. To investigate this behavior, 10 specimens representing five different glulam beam-to-column connections were tested under lateral cyclic loading. Three of the connections were custom-designed connections and two were pre-engineered connections. Specimens were large-scale glulam beam-to-column connections, and testing included combined gravity and lateral loading as well as the presence of a cross-laminated timber (CLT) deck. Connection characteristics such as yield force, initial stiffness, secant stiffness, and energy dissipation were calculated and compared across connections as well as observations made during testing. Results from the experimental testing indicated that pre-engineered connections demonstrated overall better performance than the custom connections. Pre-engineered connections had the largest remaining secant stiffness by the end of the loading protocol, greater energy dissipation, and larger average yield forces than the custom connections. Although all connections tested exceeded their lateral design capacities at drift levels less than 2% drift, all connections maintained load-carrying capacity throughout testing. [ABSTRACT FROM AUTHOR]

As oriented strand board (OSB) increases in use, improving the mechanical properties is of importance. Improved in-plane shear properties will allow for more efficient use as well as open up other opportunities in engineered wood products with high shear stresses. Based on classical laminated plate theory, composite laminates with laminate alignment patterns produce higher in-plane shear modulus and strength compared with typical alignment. Oriented strand board was manufactured 13.3-mm thick with and alignment patterns, and in-plane shear, bending, nail connection, and small-scale shear wall properties compared to commercial OSB. Results showed a 24% increase in shear modulus for the alignment when compared with the alignment using a method similar to a standard in-plane shear test. Results also show 10% reduction in bending modulus of elasticity in the parallel direction. Small-scale shear wall tests were insensitive to changes of in-plane shear properties. Lateral nail connection tests showed no reduction in connection yield load, implying that these panels can be used in similar applications without affecting connection properties. [ABSTRACT FROM AUTHOR]

Polymethylmethacrylate (PMMA) and functionalized multiwalled carbon nanotube (F-MWCNT) based composite films were prepared using solution casting method. Nanoindentation and scratch measurements were carried out to study the influence of F-MWCNT as the reinforcement on the mechanical properties of the composite at the sub-micron scale. The composites were prepared with varying weight percentages of F-MWCNT in the PMMA matrix. The composites containing an adequate amount (0.25 wt%) of F-MWCNT was found to demonstrate the maximum nanomechanical properties, viz. hardness, elastic modulus, recovery index. Scratch resistance measured in terms of coefficient of friction, also showed maximum value for the PMMA composite reinforced with 0.25 wt% of F-MWCNT. POLYM. COMPOS., 35:948-955, 2014. © 2013 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Laminated bamboo lumber (LBL) is regarded as an alternative framing material for the construction industry. However, there is limited knowledge of its behavior in connection with commonly used sheathing material, such as oriented strand board (OSB). This study characterized the lateral load carrying capacity of LBL-OSB connections and studied the applicability of the yield models presented in the national design specifications to LBL connections. Two different connection geometries, edge and plate, which were representative of those present in a wall, were analyzed. The strength of the connections was characterized using monotonic testing. After the destructive testing, portions of the framing and sheathing materials from the samples were further evaluated for dowel bearing strength. Experimental results indicate that the LBL-OSB connections have similar lateral load carrying capacity as conventional Douglas fir-OSB connections. No statistical significance was observed in the strength differences of edge and plate connection geometries. The results further indicated that existing yield models used for design of nailed connections can predict the capacity and the mode of yielding for edge connection geometry between OSB sheathing and LBL framing members of grade and dimensions considered in this study, provided that the dowel bearing capacity of the materials is known. [ABSTRACT FROM AUTHOR]

Abstract: The present investigation concerns the effect of cryogenic treatment on mechanical properties and shape recovery behavior of the Ti-rich Ti–Ni alloy. The sample quenched in liquid nitrogen (CQ) has resulted in higher volume fraction of martensite (B19′) phases and exhibited higher amount of recoverable strain (∼10%) in the region of iso-stress tensile deformation in comparison to the samples quenched in ice water. Cold rolling of the sample at near liquid nitrogen temperature (CR), with and without subsequent aging treatment, has resulted in the bimodal distribution of martensite plate size and negligible amount of recoverable strain under iso-stress tensile deformation. [Copyright &y& Elsevier]

Abstract: Iron aluminide particulate reinforced aluminium composites were prepared by a simple liquid metal stir casting route. The particulate intermetallic reinforcements were formed by in-situ reaction between molten aluminium and a rotating mild steel stirrer at 800°C. X-ray diffraction studies were carried out to identify the types of iron aluminide particulates present in the as cast composite. Compositional variations of the composite samples were estimated with the aid of energy dispersive spectroscopy. The microstructural features of the composite were studied with respect to different heat treatment schedules and deformation conditions. Microhardness and nanoindentation measurements were also carried out to assess the micromechanical behaviour e.g., hardness and elastic modulus in micrometric length scale of the composite samples. Tensile tests and fractographic analysis were performed to estimate the mechanical properties and determine the mode of failure of the samples. The microstructure and mechanical properties of the composite samples were correlated and discussed. [Copyright &y& Elsevier]

Abstract: Multi-objective genetic algorithm based searching is used for designing the process schedule of Ti-(∼49at.%) Ni alloy, to achieve optimum mechanical property and shape recovery behavior. Artificial neural network technique based data driven models are developed to empirically describe the relationship between the processing conditions and the properties. The models are used as objective functions for the optimization process. The optimization search found to be helpful to design the decision space variables for the improvement in shape recovery behavior without sacrificing the mechanical properties of the alloy. The Pareto solutions have been used as the guideline to find the process schedules, which is validated by suitable experimentation. [Copyright &y& Elsevier]

Abstract: This work aims to compare the scratch hardness with the indentation hardness of ZnO nanoparticle reinforced polymethylmethacrylate (ZnO/PMMA) composites obtained from nanoindentation measurements. 50μm thick films ZnO/PMMA nanocomposites were produced by the in-situ spin coating method. Scratch hardness was measured from the scratch width origin at low load during the course of the scratch measurements. A good correlation was found between the scratch hardness and the indentation hardness at low indentation depth, where a linear relationship between hardness and the reinforcement content of ZnO nanoparticles was observed. The composite was structurally established by transmission electron microscopy and furrier transform infrared spectroscopy. [Copyright &y& Elsevier]

Abstract: The present investigation aims to study the effect of ageing treatment on the mechanical properties and shape memory characteristics of the Ti-rich Ti–Ni alloy. The ageing treatment of the homogenized and deformed Ti-rich alloys results in the formation of Ti2Ni precipitate phase. The coarser precipitates occasionally provide the nucleation sites for the martensite plates. In the case of the deformed samples, the austenites to martensite and reverse transformations have been constrained due to the presence of deformation strain as evidenced from the corresponding XRD pattern. In the case of the aged samples, the martensitic transformation evolved through the one-stage (B2→B19′) and two-stage transformation routes via the formation of R phase. The most favorable shape recovery is achieved at the peak aged condition of the samples owing to the formation of optimum particle size conducive to delaying the onset of plastic straining. [Copyright &y& Elsevier]

Abstract: The present investigation aims to study the effect of cold deformation on the mechanical properties and shape recovery behavior of the Ti-rich Ti–Ni alloy. The micrographic investigations and XRD analyses have revealed that the microstructure of the homogenized and quenched samples comprises austenite (B2) and martensite (B19′) phases. Significant enhancement of martensite volume fractions in the microstructure has been achieved after 30% cold deformation. The effect of deformation has also been manifested in terms of the sloping tensile curve in the region of shape memory strain. The shape recovery experiment has indicated improved shape recovery ratio in the case of the deformed samples owing to the delay in onset of the plastic straining during the shape deformation. [Copyright &y& Elsevier]

Fracture toughness of wood and wood composites has traditionally been characterized by a stress intensity factor, an initiation strain energy release rate ( G) or a total energy to fracture ( G). These parameters provide incomplete fracture characterization for these materials because the toughness changes as the crack propagates. Thus, for materials such as wood, oriented strand board (OSB), plywood and laminated veneer lumber (LVL), it is essential to characterize the fracture properties during crack propagation by measuring a full crack resistant or R curve. This study used energy methods during crack propagation to measure full R curves and then compared the fracture properties of wood and various wood-based composites such as, OSB, LVL and plywood. The effect of exposure to elevated temperature on fracture properties of these materials was also studied. The steady-state energy release rate ( G) of wood was lower than that of wood composites such as LVL, plywood and OSB. The resin in wood composites provides them with a higher fracture toughness compared to solid lumber. Depending upon the internal structure of the material, the mode of failure also varied. With exposure to elevated temperatures, G for all materials decreased while the failure mode remained the same. The scatter associated with conventional bond strength tests, such as internal bond and bond classification tests, renders any statistical comparison using those tests difficult. In contrast, fracture tests with R curve analysis may provide an improved tool for characterization of bond quality in wood composites. [ABSTRACT FROM AUTHOR]

The effect of grain angle (GA) on shear strength of Douglas-fir has been evaluated. Shear block specimens with a GA varying from 0 to 90° was loaded in the shear plane, resulting in failure mode transitioning from parallel to grain shear to rolling shear. As expected, shear strength decreased as the GA increased from 0° to 90°. A root-mean-square equation was found to be suitable to predict the relationship between GA and shear strength. Traditional Hankinson formula and the Tsai-Wu criteria were less effective with this regard. [ABSTRACT FROM AUTHOR]

An attempt has been made to correlate shape memory behavior and the micromechanical characteristics of the martensite crystals in the polycrystalline microstructure of thermally and thermomechanically processed nearly equi-atomic Ni-Ti shape memory alloy. The nanoindentation measurements have shown that suitable schedule of thermo mechanical treatment improves the hardness of the martensite phase. The recovery index parameter (η) obtained from the load-depth profile illustrates the recovery of the indentation strain of the martensite phase. [ABSTRACT FROM AUTHOR]

This study investigated the effect of exposure to elevated temperature on the yield strength of single-shear nail connections when subjected to lateral loading. Solid sawn lumber and laminated veneer lumber were used as framing members and two different thicknesses of both oriented strand board and plywood were used as the sheathing members. The connection geometries evaluated were typical of those encountered in lateral force resisting systems such as shear walls or roof diaphragms. The connection geometries were (1) edge connection-nail positioned 19 mm from the panel edge, loaded parallel to the grain of the main member, and (2) plate connection-nail positioned 19 mm from the panel end, loaded perpendicular to grain of the main member. Data collected from monotonic tests on 480 nail connections, after exposure to elevated temperatures, were analyzed for yield strength. In addition, 210 dowel bearing strengths were evaluated for the same treatments. The results indicated that exposure to elevated temperature caused significant degradation in lateral yield strength after exposure. The highest degradation occurred when exposed to 200°C for 2 h. For example, for plywood (11.2 mm) and solid lumber connections, the decrease in yield strength after exposure to 200°C for 2 h was 26% for edge connections and 56% for plate connections. The results further indicated that, given thermal degradation of the dowel bearing capacity of a material, the existing yield models stipulated in National Design Specifications (NDS) can predict yield load values for nailed connections for a given sheathing and framing member combination under those thermal degradation conditions. Additionally, the yield models predicted a predominant yield mode (IIIs), consisting of a single plastic hinge being formed just beneath the surface of the thicker member. These predictions were consistent with observed yield modes. [ABSTRACT FROM AUTHOR]

The construction industry has relied heavily on wood and wood-based composites, such as oriented strand board (OSB) and plywood for timber frame construction. Therefore, it is highly imperative to categorize the response of wood-based composites when exposed to elevated temperatures for a sustained period of time. The essence of fire-resistant structural design is to ensure that structural integrity be maintained during and after the fire, prevent collapse and maintain means of egress. Another aspect is to assess post-fire structural integrity and residual strength of existing structure. The objective of this project was (a) to study the effect of exposure time on bending strength (MOR) of OSB and plywood at elevated temperatures, (b) to interpret any relationships between different temperature and time of exposure using a kinetics model for thermal degradation of strength, and (c) to develop a master curve representing temporal behavior of OSB and plywood at a reference temperature. As much as 1,152 samples were tested in static bending as a function of exposure time and several temperatures. Strength (MOR) of both OSB and plywood decreased as a function of temperature and exposure time. These results were fit to a simple kinetics model, based on the assumption of degradation kinetics following an Arrhenius activation energy model. The apparent activation energies for thermal degradation of strength were 54.1 kJ/mol for OSB and 62.8 kJ/mol for plywood. Furthermore, using the kinetics analysis along with time-temperature superposition, a master curve was generated at a reference temperature of 150°C which predicts degradation of strength with time on exposure at that reference temperature. The master curves show that although plywood has a higher initial strength, OSB performs better in terms of strength degradation after exposure to elevated temperature. [ABSTRACT FROM AUTHOR]

Wood and wood-based composites are being used extensi-vely in single-family residential dwellings. Therefore, it is important to categorize their response when exposed to elevated temperatures for a sustained period of time. In fire-resistant design for wood structures, the main goal is to ensure that enough structural integrity is maintained, during and after a fire, to prevent collapse and to maintain means of egress. Another goal is an ability to assess post-fire structural integrity and residual strength of an existing structure. The objectives of this study are: (a) to study the effect of temperature and exposure time on bending strength (MOR) and stiffness (MOE) of solid sawn lumber (SSL), laminated veneer lumber (LVL), oriented strand board (OSB) and plywood; and (b) to develop predictive relations between different temperatures and times of exposure and the thermal degradation of strength. A total of 1080 samples were tested in static bending under various heat treatments. The results indicated that exposure to elevated temperature caused significant degradation of bending strength and stiffness. A statistical regression-based model and a kinetics-based model were developed and evaluated for predicting the strength loss of wood and wood-based composites as a function of thermal exposure temperature and exposure time. The kinetics-based model fit the data better and predictions consistently matched the observed values, making the model preferred over the regression approach. [ABSTRACT FROM AUTHOR]

Abstract: We report a chemical route for the deposition of nanocrystalline thin films of CuS, using aqueous solutions of Cu(CH3COO)2, SC(NH2)2 and N(CH2CH2OH)3 [triethanolamine, i.e. TEA] in proper concentrations and ratios. The films were structurally characterized using X-ray diffraction technique (XRD), field emission scanning electron microscopy (FESEM) and optical analysis [both photo luminescence (PL) and ultraviolet–visible (UV–vis)]. Optical studies showed a large blue shift in the band gap energy of the films due to quantum confinement effect exerted by the nanocrystals. From both XRD and FESEM analyses, formation of CuS nanocrystals with sizes within 10–15nm was evident. A study on the mechanical properties was carried out using nanoindentation and nanoscratch techniques, which showed good mechanical stability and high adherence of the films with the bottom substrate. Such study on the mechanical properties of the CuS thin films is being reported here for the first time. Current–voltage (I–V) measurements were also carried out for the films, which showed p-type conductivity. [ABSTRACT FROM AUTHOR]

The overall goal of this study is to gain an insight into the load sharing aspect between oriented strand board (OSB) and gypsum wall board (GWB) in shear wall assembly during racking load. Sixteen standard 2,440×2,440 mm walls were tested monotonically, in total, out of which 11 (Type A) were sheathed on both sides (OSB on one side and GWB on the other), while five walls were tested without GWB (Type B). Digital image correlation (DIC) was used for data acquisition and analysis which is a full-field, noncontact technique for measurement of displacements and strains. The system returns full-field three-dimensional displacement and strain data measured over the visible specimen surfaces. Overall, these tests suggest that initially during loading of a wall the load is shared between OSB and GWB. However, the proportion of load sharing is not known. As GWB fails first at about 60% of ultimate load capacity of the wall, the load shifts to the OSB panel which resists it until the failure of the wall. The tests also revealed that the load path in wall Types A and B is different and so is the failure pattern. Strains were locally concentrated around the fasteners, while the strains in the field of the panel were below the detection limit of DIC system. [ABSTRACT FROM AUTHOR]

Mass ply panel (MPP) is a new mass timber product that was recently introduced for structural applications in buildings. Although there have been several studies on characterizing the mechanical properties and structural performance of MPP, there is a lack of understanding regarding in-plane shear properties of the panels. More intensive studies should be done for MPP to provide a comprehensive understanding of its behavior. This paper presents an experimental study to characterize the effective in-plane shear modulus and shear strength of MPP in the major strength direction of the panel. Two experiments, including multiple span-length center-point bending tests and a novel large-scale shear test, were conducted. The test results were presented and compared with previous studies and the manufacturer's product report. The new test proposed for shear strength characterization has the potential to be an industry standard for mass timber panels. [ABSTRACT FROM AUTHOR]

In the last several decades, there has been significant growth in research and development activities in nanomaterials. Nanotech has been used to improve the quality of several materials, including wood and polymer composites, for their application in various fields. Nanofillers, including metal particles, nano oxides, pyrogenic silica, and carbon black, have been employed as polymer additives. However, the value of natural, low-cost, and plentiful clay materials such as nanoclay becomes more apparent as environmental regulations and consumer awareness become more rigorous. This literature outlines the role of nanoclay on polymer composites, especially in the case of thermosetting resins, including epoxy, polyester, urea-formaldehyde, and phenol-formaldehyde resins. The current article is intended to provide a comprehensive source of recent studies and literature on nanoclay as filler, its classification, polymer modification processes using nanoclay, and comparing the performance of different thermosetting polymers based on their fabrication methods through physical and mechanical properties. [ABSTRACT FROM AUTHOR]

• Cross-laminated timber rocking walls dissipate energy through connection damage. • Slip-friction connections were originally developed for steel structures. • The SFC system was designed as a hold-down in a self-centering CLT rocking wall. • Quasi-static, cyclic tests with SFC connections showed elastic-plastic behavior. • Passive damping was close to typical idealized friction hysteresis models. Cross-laminated timber (CLT) rocking walls limit internal building forces and dissipate seismic energy mostly through severe connection damage and related wood crushing. While collapse-prevention and life-safety performance can be achieved, the connections and CLT walls are permanently damaged and may be unreliable for resisting aftershocks. Slip-friction connections (SFCs), also known as slotted-bolted connections, are highly resilient passive dampers originally developed for steel structures. As part of a thorough research program to apply SFCs to CLT rocking walls, connection tests were conducted to better understand a novel application of multiple modern timber technologies. The research objectives were to design and test a slip-friction connection connected to cross-laminated timber with inclined self-tapping screws (STS) to determine the stiffness and passive damping properties of the assembly. The SFC system was designed for use as a slip-friction hold-down in a self-centering CLT rocking wall system. A series of quasi-static, cyclic axial tests with slip-friction connections was shown to impart ductile and elastic–plastic characteristics to an otherwise non-ductile CLT connection. Because the timber connection forces were limited below the STS yield strength by the slip-friction connectors, no wood damage was observed during SFC sliding. Compared to other sources, passive damping was found to be excellent and close to typical idealized friction hysteresis models. The slip-friction connections are a unique design using an efficient CLT to SFC connection, with no slack, that performs consistently after consecutive tests. Additionally, cursory equivalent-viscous-damping ratios were extracted for the elastic range of the STS to steel connection for small amplitude excitations below the slip force threshold. [ABSTRACT FROM AUTHOR]

Over the past decade, cross-laminated timber (CLT) panels have gained popularity worldwide. To achieve larger spans and to increase the resistance to diaphragm seismic and wind forces to be transferred through CLT floor or roof systems, CLT-concrete composite (CCC) floors have been developed as an alternative. While significant testing has been performed under gravity loading, limited experimental data exist on the in-plane performance of CCC systems. This study presents results from an experimental program designed to characterize the in-plane shear behavior of CCC diaphragm connections using different CLT to concrete screw connector orientations in a test setup that simulates the expected seismic load path in diaphragms for platform-type construction. Tested variables include concrete slab thickness, composite screw angle, and single spline connection systems consisting of nails or screws. Experimental results and observed damage progression from cyclic testing are presented and discussed. Results indicate that CCC systems achieved increased stiffness and strength values when compared to bare-CLT systems, but slab thickness did not influence the strength and stiffness of the system for the load paths simulated. Additionally, CCC floor systems with 45° composite screw connectors displayed increased strength but overall similar stiffness values when compared to the CCC systems with 90° composite screws. The results provide useful engineering parameters, such as elastic stiffness, peak load, displacement capacity, and ductility ratios that can be used in the development of codified design parameters or in performance-based designs. [ABSTRACT FROM AUTHOR]

Mass plywood panel (MPP) is a veneer-based engineered wood product that recently was introduced in the mass-timber construction industry. Preliminary studies show that MPPs can be a preferred construction material for shear walls, floor diaphragms, and roof assemblies. However, no design guide exists regarding the use of MPPs as structural elements. This is compounded by a lack of engineering properties and parameters needed beyond the generic values provided in the product report. To assess the engineering properties and provide a benchmark dataset, a comprehensive experimental testing program characterized the performance of MPPs in flexure, in-plane shear (parallel to major strength direction), compression, and tension. Additionally, the characteristic values of MPPs were derived based on the test results to provide an initial indication of design values of MPPs. The test results presented in this study provide a fundamental basis for the development of a design guide for MPPs. [ABSTRACT FROM AUTHOR]

An optimization problem was developed by using a genetic algorithm to select wavelengths for establishing multivariate calibration models based on partial least squares (PLS) regression. Two near infrared (NIR) data sets represented by untreated and second derivative spectra were used to predict Eucalyptus globulus pulp yield. The optimization process was run with the number of variables (i.e., wavelengths) varied from 10 to 100 to determine the optimum wavelengths and number of latent variables for PLS regression model. A linear function of R-squares for calibration and prediction sets was utilized as the objective function of the optimization problem. The optimum wavelengths selected by genetic algorithm helped to considerably improve the performance of the PLS regression model, not only for the calibration sets but also for the prediction sets. The optimum number of latent variables varied over a wide range, from the maximum allowed (20) to a lower limit of six. Representative wavelengths for each data set were also statistically determined and assigned to corresponding wood components through a band assignment process, which showed strong agreement. [ABSTRACT FROM AUTHOR]

A full-scale 2-story mass timber building was tested on the University of California San Diego Natural Hazards Engineering Research Infrastructure (UCSD-NHERI) uniaxial shake table during the period from June 2017 to September 2017. The main objective of the experimental program was to test the performance of mass timber building designs with different seismic lateral force–resisting systems. The focus of this study is on a building configuration designed using self-centering post-tensioned cross-laminated timber (CLT) rocking walls with U-shaped steel flexural plate energy dissipators. The shake-table tests were designed to subject the building to a series of earthquake ground motions of increasing intensity, ranging from a service-level earthquake to 1.20 times the maximum considered earthquake intensity. Between each ground motion, low-amplitude white-noise excitations were applied to the building, which responded as a quasilinear system. In this paper, two output-only operational modal analysis methods are used to estimate the modal parameters (frequency, damping, and mode shapes) based on acceleration data collected during the white-noise shake-table tests. The correlations of observed damage and repairs performed during the experimental program with changes in estimated modal features are reported. The modal parameters estimated from the testing program are also compared with a linear finite-element model that is used to validate the modal identification results and study the performance of the two system identification methods for CLT rocking structures. [ABSTRACT FROM AUTHOR]

This paper presents the behavior of floor diaphragms of a shake-table experiment of a full-scale 2-story mass-timber building structure. The structure consists of glued-laminated timber beams and columns, and floors and walls were designed and built making use of cross-laminated timber panels. Two different floor systems were designed, where the roof consists of a topped cross-laminated timber (CLT)-concrete composite system, and the floor level consists of untopped CLT panels connected with plywood single-surface splines. The CLT floor systems were designed to remain essentially elastic over the whole series of shake-table tests, which included testing of three lateral force–resisting systems tested at three different seismic intensity levels (service level, design basis, and maximum considered earthquake) for a total of 34 shake-table earthquake tests. Results from the testing indicate that CLT diaphragms designed to remain essentially elastic based on basic principles of structural mechanics and existing test data can achieve desired seismic performance objectives. In addition, sources of overstrength in certain elements of the diaphragm need to be explicitly considered for a holistic diaphragm design. [ABSTRACT FROM AUTHOR]

Consistent with the diagnosis-to-randomization analysis, patients with DS <=7 days were more likely to have adverse disease characteristics (e.g. double-hit lymphoma, bulky disease, high LDH, and fever) than those with longer DS (Table 1). Novel treatment regimens combining chemotherapy with targeted agents are being developed for diffuse large B-cell lymphoma (DLBCL). Our findings suggest that treatment delay due to biomarker testing does not affect outcome on this model, and should not preclude enrollment of patients into clinical trials. In step 2 of the 2-step analysis model, median SR time in patients with more aggressive disease (patients with DS <=7 days) was 7 days (range 1-26 days). [Extracted from the article]

Timber–concrete composite (TCC) floors exposed to fire experience charring and thermal degradation of timber, leading to a reduction in load-carrying capacity. Finite element (FE) modeling supplements data from experimental fire testing and allows for fast and economical investigation of additional design parameters. This research presents fire test results of three large-scale TCC floor specimens and development of an FE modeling methodology for TCC floors in a fire. TCC floors constructed with nail-laminated timber, cross-laminated timber, or mass ply panel, with truss plates or angled screws as shear connectors, are loaded with a uniformly distributed service-level live load and exposed to the ASTM E119-20 standard fire curve. A 2D FE modeling methodology is presented and benchmarked against the test data. The methodology integrates sequentially coupled thermal-structural analyses, which make use of temperature-dependent thermal and mechanical properties of timber and concrete. The deflection and failure times of the FE models are benchmarked against test data. Connector forces from FE models show that shear connectors remain elastic throughout the fire exposure. FE results indicate that the load-carrying capacity is dependent on tensile stress redistribution to the uncharred timber section. The FE modeling methodology effectively calculates the mechanical and fire behavior of TCC floors and highlights limits of the applicability of analytical design methods. [ABSTRACT FROM AUTHOR]

Context: There is scarcity of data on thyroid function abnormality in COVID-19 patients in world literature. Aims: The objective of this study was to assess thyroid function tests in hospitalized patients of COVID-19. Settings and Design: Sixty (60) patients with COVID-19 detected by RT-PCR admitted in General Medicine isolation ward and COVID block of a tertiary care teaching hospital were selected by semi-purposive sampling. Materials and Methods: These patients were assessed for thyroid function tests, including total T3, free T3, total T4, free T4, TSH and anti-TPO antibody along with other baseline investigations. Patients with pre-existing thyroid–related ailments, those on levothyroxine or anti-thyroid drugs or other drugs known to interfere with the results were excluded. Results: There were 43.3% patients in mild, 26.7% in moderate, and 30% in severe category, according to local COVID-19 severity classification protocol. 35% patients had one or more abnormality in the thyroid function, low TSH being the most common (18.33%). 9.1% patients had characteristic pattern of thyroiditis. In most of the others thyroid function did not match any typical pattern. There was no significant difference in any of the parameters of the thyroid function test between mild, moderate, and severe groups. Conclusion: Thyroid function may be abnormal in all categories of patients during COVID-19 infection, even in absence of pre-existing thyroid ailments. Although low TSH is the commonest abnormality and typical pattern of thyroiditis can be seen in a subsection of patients, in majority of the patients, thyroid function abnormality does not follow any characteristic pattern and likely represents a combination of thyroiditis and sick euthyroid syndrome in different points of its spectrum. [ABSTRACT FROM AUTHOR]

Purpose: Because of the mechanical properties of aluminium (Al), an accurate prediction of its properties has been challenging. Researchers are seeking reliable models for predicting the mechanical strength of Al alloys owing to the continuous emergence of new Al alloys and their applications. There has been widespread use of empirical and statistical models for the prediction of different mechanical properties of Al and Al alloy, such as linear and nonlinear regression. Nevertheless, the development of these models requires laborious experimental work, and they may not produce accurate results depending on the relationship between the Al properties, mix of other compositions and curing conditions. Design/methodology/approach: Numerous machine learning (ML) models have been proposed as alternative approaches for predicting the strengths of Al and its alloys. The hardness of Al alloys has been predicted by implementing various ML algorithms, such as linear regression, ridge regression, lasso regression and artificial neural network (ANN). This investigation critically analysed and discussed the application and performance of models generated by linear regression, ridge regression, lasso regression and ANN algorithms using different mechanical properties as training parameters. Findings: Considering the definition of the problem, linear regression has been found to be the most suitable algorithm in predicting the hardness values of AA7XXX alloys as the model generated by it best fits the data set. Originality/value: The work presented in this paper is original and not submitted anywhere else. [ABSTRACT FROM AUTHOR]

Background: Humans are accidental hosts in the zoonotic disease Scrub typhus. The disease though widespread in our county, it remains grossly underdiagnosed because of its non-septic clinical manifestations and lack of access to specific laboratory facilities. Aims and Objectives: The objective of present study is to evaluate the clinical presentations of Scrub Typhus among the study group. Furthermore, to assess the various laboratory findings in Scrub Typhus cases among the study group is the other objective of this study. Materials and Methods: The present study is an Institution-based, observational, and cross-sectional study conducted for 18 months with the admitted patients having 14-70 years of age. Data collected regarding patients' demographic profile, symptoms, clinical findings, laboratory, and radiological findings. Data had been summarized as mean and standard deviation for numerical variables and count and percentages for categorical variables. Results: In our study, we found that most of the patients were 14-20 years old and female population was higher. It was found that 34.3% of patients had Eschar, 42.9% of patients had Rash, and 91.4% of patients had Pallor, 8.6% of patients had Ascites, 25.7% had Edema, 8.6% of patients had Jaundice, 11.4% had shock, and 57.1% had pneumonia/pneumonitis. The present study showed that 65.7% of patients had drug response (Doxycycline). Conclusion: Knowledge of geographical distribution, evidence of exposure to vector, clinical features such as fever, rash, eschar, headache, and myalgia along with high index of suspicion are crucial factors for early diagnosis and that helps in timely treatment of the cases. [ABSTRACT FROM AUTHOR]

Prediction of pulp yield of Eucalyptus globulus wood samples based on partial least squares (PLS) regression can be optimized by utilizing specific near infrared (NIR) wavelengths. A critical feature of this approach is the weighting of constraint conditions. Equal weighting balances optimization in terms of calibration and prediction; however, there is a lack of knowledge regarding prediction performance of wood property models when different weight factors are used. In this study, pulp yield models were developed using two E. globulus data sets characterized by narrow (5%) and extreme (22.6%) yield ranges and represented by untreated and second derivative NIR spectra. The global optimization solver pySOT was used to optimize the performance of a PLS regression model in terms of wavelengths selected and number of latent variables. A linear function of R-squares for calibration ( R c 2 ) and prediction ( R p 2 ) sets was utilized as the objective function with the aim of maximizing α R c 2 + 1 - α R p 2 for all values of α between 0 (maximizing R p 2 without concern for R c 2 ) and 1 (only maximizing R c 2 ). Values of α ≤ 0.8 provided good predictive performance, whereas α ≥ 0.9 tended to overfit the calibration data indicating that models are robust for values of α from 0 to 0.8. Representative wavelengths for each data set were identified and assigned to corresponding wood components through a band assignment process. Strong agreement was observed for α ≤ 0.8 ; however, for α ≥ 0.9 , identified wavelengths generally occurred in regions unrelated to vibrations arising from specific wood components. [ABSTRACT FROM AUTHOR]