Treesearch

Wood can be coated with a clear finish, stained or painted to provide protection from water and ultra violet energy. In this case the coating and wood are two different phases that coexist. Another approach is to provide protection by “coating” in the surface not on the surface. Such an approach is referred to as an envelop rather than a coating. This can be done in several ways including cold plasma surface functionalization, monomer-polymer surface impregnation, surface chemical modification, combination of polymer-chemical modification, high temperature surface chemical conversions,...

To design effectively for durability, one must actively and honestly assess the material properties and limitations of each of the components in the design system; wood or wood composite, and the coating. Inasmuch as wood coatings are manufactured to specified tolerances from known materials, we have control of that component of the system. Compared to manmade substrates such as steel, with wood we have virtually no control over the material properties of the substrate in coated wood systems. Despite this lack of control, with sufficient understanding of wood and the wood--coating interface...

Timber bridges are often viewed by engineers as less durable than steel or concrete structures. However, they remain a durable and economical option along secondary roads in many rural areas of the country. With well over 75,000 bridges listed by the Federal Highway Administration’s National Bridge Inventory as having timber superstructures as of 2002, they represent about 15% of the nation’s highway bridges. Many of these timber bridges have been in service for more than 50 years. Knowledge of their long-term performance characteristics will allow maintenance and repair practices to be...

The performance of 35 finishes (clear water-repellent Preservatives; lightly pigmented, water-repellent preservatives; semitransparent stains; solid-color stains; and paints) applied to newly planed vertical-grained; factory-planed, flat-grained; or saw-textured, vertical-grained western redcedar bevel siding was evaluated for cracking, erosion, and general appearance over 14 years of outdoor exposure at two sites (Madison, WI, and Gulfport, MS). Service life was dependent on the wood surface and increased in the following order: clear water-repellent preservatives; lightly pigmented,...

The cellulose nanofibrils that are found in wood and other natural materials are similar to carbon nanotubes in many ways and could be used to strengthen composites for manufacturing.

Wood is a hygroscopic material which contains water in varying amounts, depending upon the relative humidity and temperature of the surrounding atmosphere. Equilibrium conditions are established as shown in Table 6.7.1. The standard reference condition for wood is oven-dry weight, which is determined by drying at 100 to 105°C until there is no significant change in weight.

Stress-graded structural lumber is produced under two systems: visual grading and machine grading. Visual structural grading is the oldest stress grading system. It is based on the premise that the mechanical properties of lumber differ from those of clear wood because many growth characteristics of lumber affect its properties: these characteristics can be seen and judged by eye (ASTM D 245). The principal growth feature affecting lumber properties are the size and location of knots, sloping grain, and density.

Structural panel products are a family of wood products made by bunding veneer, strands, particles, or fibers of wood into flat sheets. The members of this family are (1) plywood, which consists of products made completely or in part from wood veneer; (2) flakeboard, made from strands, wafers, or flakes; (3) particleboard, made from particles; and (4) fiberboard and hardboard, made from wood fibers. Plywood and flakeboard make up a large percentage of the panels used in structural applications such as roof, wall, and floor sheathing; thus, only those two types will be described here.

In the natural ecosystem, wood residues are recycled into the nutrient web through the action of wood-degrading fungi, insects, and other organisms. In some circumstances, these same natural recyclers have the potential to degrade wood used in construction. Termites and decay fungi are the most destructive, but other organisms, such as wood boring beetles and carpenter ants, can be important in some regions. Several types of marine organisms can attack wood used in brackish water and saltwater. If conditions are favorable for the survival of one or more of these wood- destroying organisms,...

Pleodendron costaricense N. Zamora, Hammel & R. Aguilar (Canellaceae) is an endemic species from the southern Pacific region of Costa Rica. It is rare and is considered to be a living fossil. The wood of P. costaricense has high density (0.92 Kg/cm3, air dry) with little distinction between heartwood and sapwood. The growth rings are marked by tangential rows of fibers. Its porous are diffuse with moderately few, small, very long vessel elements and scalariform intervessel pitting. Vessels are solitaries with scalariform perforations having 20-40 bars. Rays are uniseriate and homocellular....