Treesearch

Finite element analysis is used to simulate cone indentation creep in materials across a wide range of hardness, strain rate sensitivity, and work-hardening exponent. Modeling reveals that the commonly held assumption of the hardness strain rate sensitivity (mΗ) equaling the flow stress strain rate sensitivity (mσ) is violated except in low hardness/modulus materials. Another commonly held assumption is that for self-similar indenters the indent area increases in proportion to the (depth)2 during creep. This assumption is also violated. Both violations are readily explained by noting that...

The desirability of specific wood properties is driven by a number of social, economic, and environmental factors that influence wood-use trends. This article discusses current continuing commercial uses of wood, significant new or emerging commercial uses, and desirable wood properties indicated by projected changes in wood use. Emerging issues and applications such as carbon markets/carbon sequestration, production of renewable energy, chemical feedstock production, and production of nano-enabled materials and products are expected to increasingly shape wood use as the 21st century...

Foward -- The development of high-value wood and fiber products is one of the most important challenges currently facing the forest industry. Traditional pulp and paper products are on a critical path in developed countries with prices and markets decreasing. Finland and the USA have faced the same problem, which is a fundamental reason for Industrial Biomaterials being one of VTT’s four spearhead programmes. The programme focus is precisely on the development of sustainable fiber-based products which generate added value for wood. Forestcluster Ltd works in the same directions and...

We present advances on the development of a mechatronically and algorithmically automated framework for the data-driven identification of constitutive material models based on energy density considerations. These models can capture both the linear and nonlinear constitutive response of multiaxially loaded composite materials in a manner that accounts for progressive damage.

The rheological properties of acid hydrolyzed corn stover at high solids concentration (20–35 wt.%) were investigated using torque rheometry. These materials are yield stress fluids whose rheological properties can be well represented by the Bingham model. Yield stresses increase with increasing solids concentration and decrease with increasing hydrolysis reaction temperature, acid concentration, and rheometer temperature. Plastic viscosities increase with increasing solids concentration and tend to decrease with increasing reaction temperature and acid concentration. The solids concentrati...

In order to quantify the effect of temperature on the mechanical properties of hemp fiber polypropylene composites, formulations containing 25% and 40% (by weight) hemp fiber were produced and tested at three representative temperatures of 256, 296, and 336 K. Flexural, tensile, and impact tests, as well as dynamic mechanical analysis, were performed and the reduction in mechanical properties were evaluated. Impact resistance was independent of temperature, whereas flexural and tensile properties were strongly affected. The highest reductions were observed in stiffness (modulus) values and...

A visitor to the San Dimas Experimental Forest might be forgiven for wondering where the trees are. It’s not that San Dimas doesn’t have trees; the native chaparral that furs the canyonsides has a lot of scrub oak—technically a tree—amid chamise, ceanothus, and toyon. Moister riparian grottos support laurel, sycamore, and alder. And clinging to the edges of roads are a few specimens of incense-cedar and Coulter pine, exotics brought in by early foresters.

The goal of this study was to gain an understanding of the environmental impact for softwood lumber production through a gate-to-gate life-cycle inventory (LCI) of softwood sawmills in the northeastern and north central United States (NE/NC). Primary mill data were collected per Consortium on Research for Renewable Industrial Material (CORRIM) Research Guidelines (CORRIM 2001). Life-cycle analysis is beyond the scope of the study.

A brief history of paint research at the Forest Products Laboratory (FPL) in Madison, Wisconsin, sets the stage for a discussion of testing paint on wood and wood products. Tests include laboratory and outdoor tests, and I discuss them in terms of several degradation mechanisms (loss of gloss and fading, mildew growth, extractives bleed, and cracking, flaking, and peeling). The paper is not a review of standard tests, but rather a summary of my opinions and recommendations for focusing tests to obtain specific information on finish performance on wood.

Reductions in hygroscopicity, increased dimensional stability and decay resistance of heat-treated wood depend on decomposition of a large portion of the hemicelluloses in the wood cell wall. In theory, these hemicelluloses are converted to small organic molecules, water and volatile furan-type intermediates that can polymerize in the cell wall. Reductions in hygroscopicity and improved dimensional stability of acetylated wood depend on esterification of the accessible hemicelluloses in the cell wall reducing hydrogen bonding with water and bulking the cell wall back to its green volume....