Effect of Sample Geometry on EMC And Moisture Hysteresis of Red Oak (QUERCUS SP.)

Past researchers have shown that equilibrium moisture content (EMC) is influenced by mechanical stress. It has also been widely demonstrated that the size effect in drying produces varying amounts of stress. This experiment related the internal stress developed during drying to the EMC of red oak (Quercus sp.) samples. The results indicated that larger pieces, with larger potential differential stresses, had significantly different EMCs than relatively smaller pieces. The influence of sample size on hysteresis ratio was also examined. The difference between the adsorbing and desorbing EMCs increased with sample size. As sample thickness decreased to 50 μm, the hysteresis ratio reached unity. Thus as internal drying stresses were eliminated from the wood, the hysteresis effect was eliminated. This behavior suggests that differential drying stresses and/or strains are a causal agent for the observed moisture hysteresis in wood

STEM Faculty Experience Teaching Students With Autism

College students who have an autism spectrum condition study in STEM fields at a higher rate than their neurotypical peers, and they face documented challenges in postsecondary education. Given the proportionally higher representation of autism in STEM majors, it is important to study what works best, from an educational standpoint, for this diverse group of students. The purpose of this qualitative study is to document the experience and insight of college faculty about unique learner qualities related to autism and the qualities most needed in STEM fields. In-depth interviews were conducted with 12 STEM faculty members about their experience teaching students on the spectrum, and thematic analysis was conducted to identify shared faculty perceptions. Faculty views converged on certain observable strengths, challenges, and general traits needed in their fields. The discussion summarizes findings and includes implications for teaching and postsecondary programming

Technical Note: A Preliminary Study on the Bending Stiffness of Chemically Treated Wood Material for Structural Composite Lumber

This research explored the effect of a chemical treatment on the stiffness of three southern hardwoods, yellow-poplar, sweetgum, and red oak, with the aim of broadening the potential feedstocks for structural composite lumber. Water-saturated 3 × 15 × 150 mm samples from each species were heated at 150° C for 30 min in three solutions: 1.0% H2SO4, water, and 1.0% NaOH. The specimens were nondestructively tested by static bending before and after treatment, and the reduction in modulus of elasticity (MOE) was determined. A significant interaction was present between the species and solutions. The trend in mean response for each species was generally a quadratic function of the solution. MOE was reduced the least for each species exposed to water. Sweetgum had a higher reduction in MOE in all three solutions, being significantly greater in the alkaline solution

CASE STUDY OF 3-PLY COMMERCIAL SOUTHERN PINE CLT MECHANICAL PROPERTIES AND DESIGN VALUES

This work elucidates on a case study of industrially manufactured cross-laminated timber (CLT). Two methods are used to calculate specimens section modulus: Sgross and Seffective. The first assumes that specimens behave as a continuous material, whereas the second considers the cross laminations (shear analogy method). Although the shear analogy method is indicated for construction purposes, applications, such as trench shoring, matting, and work platforms, could benefit from a simpler calculation method. There- fore, theobjective of this work was to conduct a case study of Modulus of Rupture (MOR) and Modulus of Elasticity (MOE) of southern pine CLT to compare the previously mentioned calculation methods. Both parametric and nonparametric fifth percentiles and associated Fb values are reported and were substantially higher than those of the constituent lumber. For MOE, empirical testing and calculation based on gross moment of inertia provided lower values as compared with the constituent lumber

USING NONDESTRUCTIVE TESTING TO IDENTIFY PREMIUM GRADES IN SOUTHERN PINE AND DOUGLAS-FIR UTILITY CROSSARMS

Unlike lumber, wood utility crossarms are not currently available in premium grades that indicate a higher level of performance in service.  Previous research has shown that nondestructive testing (NDT) techniques are able to predict performance properties of solid wood products with considerable accuracy. The aim of this study was to determine the suitability of NDT methods for predicting the stiffness and strength properties of wood utility crossarms and possibly aiding in the identification of a premium grade that exhibits higher average performance values. Samples of Douglas-fir and southern pine were subjected to multiple NDT technologies to estimate modulus of elasticity (MOE).  Each specimen was also measured for MOE and modulus of rupture (MOR) with a static bending test.  Bivariate correlations and corresponding R2 values showed that Fibre-gen’s Director HM200 and Metriguard’s E-computer were the most accurate NDT devices among those tested for predicting both MOR and MOE.  Means tests also suggested that the devices could possibly be used to identify a premium grade that shows significantly higher average performance values

Assessment of Forest Products Undergraduate Education in the United States

Traditional Forest Products/Wood Science programs have been curtailed and/or merged into other programs at many universities during the last 10 yr. Current economic challenges throughout the nation are continuing this trend. This trend is somewhat alarming when one considers the implications for education and development of the next generation of scientists in this very critically important field. If proper training programs and adequate professionals are not available, the conservative, wise, and perpetual utilization of renewable natural resources could be compromised for future generations

Use of Longitudinal Vibration and Visual Characteristics to Predict Mechanical Properties of No. 2 Southern Pine 2 × 8 and 2 × 10 Lumber

The objective of this study was to evaluate the accuracy of single MOE and MOR and combined mechanical properties with visual characteristics to improve the prediction of 2 x 8 and 2 x 10 No. @ southern pine lumber. This study evaluated the following variables: nondestructive tests, knots (knot diameter ratio [KDR] and knot area ratio), density, and mechanical properties (stiffness [MOE] and strength [MOR]). A total of 486 pieces were used, and linear regression models were constructed using stepwise selects to determine the best variables to estimate the MOE and MOR of southern pine lumber. The best single predictor for MOE and MOR was dynamic MOE (dMOE) followed by density. Among the two knot measurement methods used, the KDR best predicted stiffness and strength. For predicting the MOE, the variables dMOE, density, and KDR. The results showed that the addition of knot measurements to the models is able to improve the prediction of mechanical properties

THE INFLUENCE OF FOAM DISCONTINUITY IN THE SHEAR ZONE OF STRUCTURAL INSULATED PANEL BEAMS

The effect of foam discontinuity in the shear zone of structural insulated panel (SIP) beams was investigated in the current research. Two depths of 15.24 cm and 31.11 cm (6.5 in and 12.25 in) (SIPs) were evaluated in 1/3-point bending. Panels were sawn into beams, each approximately 29.84 cm (11.75 in.) wide, for mechanical testing. Half of the panels had joints or discontinuities in the foam layer in a location that was subject to shear stress during the bending tests. Half of the panels had joints or discontinuities in the foam layer in a location that was subject to shear stress during the bending tests. Half of the panels did not have joints or discontinuities in the foam layer in the locations that were subject to shear stress during the bending tests. The specimens with no foam discontinuity, stressed in shear, were approximately twice as strong as the specimens with a foam discontinuity. This finding has implications for routine testing and evaluation as well as for allowable properties. In the case of routine testing, foam discontinuities should purposefully be located in the zone of maximum shear as these appear to be a limiting factor. In cases where a producer manufactures SIPs with zero discontinuities, it may be prudent to seek premium value as those panels would achieve superior properties. Keywords: Structural insulated panels (SIPs), shear stress, bending test, foam, joints and routine testing.

Comparison of Nondestructive Testing Methods for Evaluating No. 2 Southern Pine Lumber: Part B, Modulus of Rupture

The identification of strength-reducing characteristics that impact modulus of rupture (MOR) is a key differentiation between lumber grades. Because global design values for MOR are at the fifth percentile level and in-grade lumber can be highly variable, it is important that nondestructive evaluation technology be used to better discern the potential wood strength. In that manner, higher-performance pieces could potentially be identified and their value captured accordingly. In this study, laboratory tests of three nondestructive testing (NDT) technologies and destructive four-point static bending were applied to 343 pieces of visually graded No. 2 southern pine lumber in the 38140 mm2 (n . 86), 38186 mm2 (n . 112), 38236 mm2 (n . 91), and 38 287 mm2 (n . 54) sizes collected across the southeast region of the United States. The NDT tests included continuous lumber test in continuous proof bending (MetriguardModel 7200 High Capacity Lumber Tester), transverse vibration (Metriguard E-Computer), and two longitudinal stress wave tools (Falcon A-Grader and Fiber-gen Director HM200). Following nondestructive tests, the specimens were destructively tested in four-point static bending. Single-predictor linear correlations were observed between static bending MOE and MOR value; and NDT outputs and bending MOR value. The regression results showed that the average NDT outputs (r2 . 0.23-0.28) had lower performance than static bending MOE (r2 . 0.39), for predicting the bending MOR of sawn lumber.