Treesearch

In the fourth quarter the U.S. housing markets improved incrementally from quarter three. Total permits, single-family starts, new house sales, and single-family spending all improved modestly quarter-over-quarter. The majority of sectors increased on a year-over-year basis as well; only multifamily starts decreased, albeit minimally. Viewed from a recent historical context, all housing construction subsectors exceeded the record lows recorded in the 2008 to 2011 time period.

Cellulose nanocrystals (CNCs) are routinely produced as aqueous suspensions. These are then typically freeze-dried in order to be added into polymeric composites using melt-blending. However, dispersing freeze-dried CNCs into hydrophobic polymers is a challenge. In this study, our objective was to advance our understanding of the impact of freeze-drying methods on the morphology of dried cellulose nanocrystals (CNCs), and on the tensile properties of the resulting PLA-CNC nanocomposites. CNCs were prepared as aqueous suspensions with 10.7% solids content using a sulfuric acid method, and...

The objectives of this study were to investigate the wear behavior of drill bits in wood drilling resistance measurements and to understand how the blunting of the cutting edges may affect the cutting forces and ultimately the measurement results. Laboratory resistance drilling experiments were conducted using an IML-RESI PD 400 tool (IML Instrumenta Mechanik Labor GmbH, Wiesloch, Germany) and a standard spade-type drill bit. Results were based on 375 drillings made on a 2.58 m long, freshly cut, defect-free yellow birch (Betula alleghaniensis) log with an average MC of 55.5%, an average...

The objective of this study was to determine the technical feasibility of combining acoustic wave data with high-resolution laser scanning data to improve the accuracy of defect detection and quality assessment in hardwood logs. Using acoustic impact testing and high-resolution laser scanning techniques, 21 yellow poplar logs (Liriodendron tulipifera) obtained from the central Appalachian region were evaluated for internal and external defects. These logs were then sawn into boards and the boards were visually graded based on the National Hardwood Lumber Association grading rules. The...

The objective of this study was to determine the technical feasibility of combining acousticwave data with high-resolution laser scanning data to improve the accuracy of defect detection and quality assessment in hardwood logs. This article (Part 1) focused on exploring the potential of an acoustic impact testing method coupled with advanced waveform analysis to detect internal decay of hardwood logs and classify logs in terms of log quality and potential board grade yields. Twenty-one yellow-poplar (Liriodendron tulipifera)logs obtained from the Central Appalachian region were evaluated...

Durability of wood products intended for use in outdoor aboveground applications are evaluated using one or more standardized test methods. These methods use relatively small specimens in an effort to accelerate decay growth and allow detection of decay. In this study, we evaluated internal moisture content and temperature of standardized specimens and compared them with specimens of a simulated post and beam connection that is recommended for residential deck construction. Specimens of each type were cut from end-matched Southern Pine timbers and exposed above ground at a test site near...

This research focused on evaluating the bending stiffness and strength of structural lumber with transverse vibration nondestructive testing techniques. A random sample of nominal 2-in.- (standard 38-mm-) thick Southern Pine dimension lumber was obtained from several mills in southeastern United States. After conditioning, the lumber specimens were nondestructively tested using transverse vibration techniques. Modulus of elasticity (MOE) was determined using the frequency of oscillation and density. Static bending MOE and strength were then determined for each specimen. Statistical...

The stabilization kinetics of polyacrylonitrile-co-methacrylic acid (PAN-co-MAA) and cellulose nanocrystal (CNC) composite films were studied with up to 40 wt% CNC loading using differential scanning calorimetry (DSC). It was determined that the addition of CNC reduced the activation energy of the polyacrylonitrile cyclization reaction by 16% irrespective of the CNC loading in the range of 5e40 wt%. There was also a development of a new exothermic peak in the PAN-co-MAA/CNC composite films after cyclization not seen in the neat PAN-co-MAA and neat CNC samples, indicating a different set of...

This study focused on the penetration of adhesive into cell lumens and cell walls. Douglas-fir samples containing an iodinated phenol-formaldehyde adhesive were analyzed using nano-X-ray computed tomography (XCT), X-ray fluorescence microscopy, and energy-dispersive X-ray spectroscopy to observe adhesive penetration in cell walls. A gradient of penetration was observed within the cell wall structure. In addition, these nano-XCT datasets were indexed to previous micro-XCT datasets, which gave the ability to link the nanoscale cell wall penetration to microscale penetration in to the porous...

Elastomeric sealants are vital to the construction of energy efficient and water tight buildings. Sealants are a small fraction of the construction budget. Upon failure their removal and reinstallation, and repair of moisture/mold damage can run in to the 10’s of millions with the added risk of illness based litigation. In this research program we are seeking to discern the significance of environmental and strain effects on sealant durability as well as the initial state of stress (aka installation/cure conditions). Sealant bonded specimens are fixtured on automated test instruments and...