STRUCTURAL ENGENEERING

Composite construction 
Is a generic term to describe any building construction involving multiple dissimilar materials. Composite construction is often used in building aircraft, watercraft, and building construction. There are several reasons to use composite materials including increased strength, aesthetics, and environmental sustainability. It is not to be confused with the composite order which is a specific order of classical architecture that combines elements of the Ionic and Corinthian orders.

Structural Engineering 
In structural engineering, composite construction exists when two different materials are bound together so strongly that they act together as a single unit from a structural point of view. When this occurs, it is called composite action. One common example involves steel beams supporting concrete floor slabs. If the beam is not connected firmly to the slab, then the slab transfers all of its weight to the beam and the slab contributes nothing to the load carrying capability of the beam. However, if the slab is connected positively to the beam with studs, then a portion of the slab can be assumed to act compositely with the beam. In effect, this composite creates a larger and stronger beam than would be provided by the steel beam alone. The structural engineer may calculate a transformed section as one step in analyzing the load carry capability of the composite beam.

Composite Wood DeckingThe traditional decking material is pressure treated wood. The current material many contractors choose to use is composite decking. This material is typically made from wood-plastic composite or Fiberglass Reinforced Plastic (FRP). Such materials do not warp, crack, or split and are as versatile as traditional pressure treated wood. Composite decking is made through several different processes, and there are a multitude of sizes, shapes, and strengths available. Depending on the type of composite selected the decking materials can be used for a number of other construction projects including fences and sheds.

Composite Steel Deck
 In a composite steel deck, the dissimilar materials in question are steel and concrete. A composite steel deck combines the tensile strength of steel with the compressive strength of concrete to improve design efficiency and reduce the material necessary to cover a given area. Additionally, composite steel decks supported by composite steel joists can span greater distances between supporting elements and have reduced live load deflection in comparison to previous construction methods 

Structural analysis is the determination of the effects of loads on physical structures and their components.

Structures subject to this type of analysis include all that must withstand loads, such as buildings, bridges, vehicles, machinery, furniture, attire, soil strata, prostheses and biological tissue. Structural analysis incorporates the fields of applied mechanics, materials science and applied mathematics to compute a structure's deformations, internal forces, stresses, support reactions, accelerations, and stability. The results of the analysis are used to verify a structure's fitness for use, often saving physical tests. Structural analysis is thus a key part of the engineering design of structures.

- Wikipedia.

COMPOSITE LUMBER

Composite lumber is a material that is a mixture of wood fiber, plastic, and some type of binding agent. These ingredients are put together to form a material that is denser, stronger, and heavier than wood alone, a wood-plastic composite.

Working with composite lumber is similar to working with wood. However, composite lumber has the added benefit of being less likely to split or denominate. Some composite lumber is also engineered to be lighter weight for easier handling. Composite lumber is also more stain, scratch, and mold resistant, and is therefore supposed to have a longer life than wood lumber.

Composite lumber comes from the manufacturer as a finished product. There is no need to stain, sand, or paint the material. Composite materials usually cost more than lumber, but their long life and low-maintenance requirements could make them more economical in the long run. Many composites are often made partially out of recycled plastics and waste wood, such as Trex Decking, which makes them an environmentally friendly, efficient use of resources.

The growth of wood-alternative products continues to fuel a debate about their environmental value when compared to wood, treated wood, metal and other alternatives. Many suggest that wood decking is made from a more sustainable ingredient and that it carries a smaller manufacturing carbon footprint.

Others have claimed that the sawing of wood-alternative products during construction creates dust that will not biodegrade and that the wood-alternative deck boards, when they have outlived their useful lives, will not biodegrade in landfills.

- Wikipedia 

COMPOUNDING AND EXTRUSION OF WOOD PLASTIC COMPOSITES

This promising and evolving technology is marked by a variety of approaches to compounding and end product extrusion. In these diagrams, the term "wood" is used to identify any of the many forms of organic material used in these processes.

1. Pre-dried wood along with resin/regrinds and additives all enter at the throat of a twin screw pelletizing extruder.	2. Pre-dried wood enters at twin screw pelletizing extruder throat with resin/regrind and additives introduced along the barrel.
3. Continuous mixer discharges dry wood at twin screw extruder throat with resin/regrind and additives introduced along barrel to produce end product profile.	4. A high-speed compounding extruder supplies multiple single or twin screw profiling extruders. Alternatively, compounding extruder feeds a gear pump to produce the profile.
5. Wood enters twin screw extruder throat and is dried within the extruder. www.ktron.com	6. Multi-extrusion application with wood and resin, regrind, and additives on main twin screw extruder with single screw extruders discharging to die head.

WOOD PLASTIC COMPOSITE

Wood-plastic composites may be one of the most dynamic sectors of today's plastic industry. Although the technology is not new, there is growing interest in the new design possibilities this marriage of materials offers.

The production of Wood-Plastic Composites typically uses a fine wood waste (cellulose based fiber fillers such as hardwood, softwood, plywood, peanut hulls, bamboo, straw, etc.) mixed with various plastics (PP, PE, PVC). The powder is extruded to a dough like consistency and then extruded to the desired shape. Additives such as colorants, coupling agents, stabilizers, blowing agents, reinforcing agents, foaming agents, and lubricants help tailor the plastic end product to the target area of application. With up to 70 percent cellulose content, wood-plastic composites behave like wood using conventional woodworking tools. At the same time, they are extremely moisture-resistant. There is little or no water present, thus increasing resistance to rot. Wood-plastic composites are already widespread in outdoor use for decking, cladding, park benches, etc. There is also a growing market for potential indoor uses such as door frames, trim and furniture.

Products include: Lumber, decking and railing, window profiles, wall studs, door frames, furniture, pallets, fencing, docks, siding, architectural profiles, louvers, automotive components.

Characteristics

• Fastest growing sector of plastics industry
• Volume processors must produce faster, better, cheaper
• Weather ability and life cycle costs are major factors
• Formulation variations that increase wood content offer expansion into other uses
• Environmentally safe and efficient

Key Blending Considerations in Wood-Plastic Composites

Compared to many other processes, on-line compounding and extrusion exhibit short performance timescales, consistent with the mixing time of the extruder. For high formulation quality the feeding system must achieve and maintain its required blending accuracy within this brief time.

Key to a feeder's ability to attain high accuracy over short intervals is the resolution of its weighing device and response of its process controller.  As the illustration at right shows, lengthy performance timescales permit a given blending accuracy to be attained with a low performance weighing system. However, to achieve the same accuracy in the short interval characteristic of compounding and extrusion operations, a much higher weighing performance is required.  Additional important blending system considerations in wood/plastic composite processing include control and weigh system insensitivity to environmental disturbances, and the ability to reliably handle/control difficult organic components.

-www.ktron.com

WOOD PLASTIC COMPOSITE- COMPOSITE MATERIAL

Wood plastic composite

Wood-plastic composites (WPCs) are composite materials made of wood fiber / wood flour and thermoplastic(s) (includes PE, PP, PVC etc.).

Chemical additives seem practically "invisible" (except mineral fillers and pigments, if added) in the composite structure. They provide for integration of polymer and wood flour (powder) while facilitating optimal processing conditions.

In addition to wood fiber and plastic, WPCs can also contain other ligno-cellulosic and/or inorganic filler materials. WPCs are a subset of a larger category of materials called natural fiber plastic composites (NFPCs), which may contain no cellulose-based fiber fillers such as pulp fibers, peanut hulls, bamboo, straw, digestate, etc - Wikipedia 

Wood Plastic Composites (WPCs) are produced by thoroughly mixing ground wood particles and heated thermoplastic resin. The most common method of production is to extrude the material into the desired shape, though injection molding is also used. WPCs may be produced from either virgin or recycled thermoplastics including HDPE, LDPE, PVC, PP, ABS, PS, and PLA. 

Polyethylene based WPCs are by far the most common. Additives such as colorants, coupling agents, UV stabilizers, blowing agents, foaming agents, and lubricants help tailor the end product to the target area of application. Extruded WPCs are formed into both solid and hollow profiles. A large variety of injection molded parts are also produced, from automotive door panels to cell phone covers.

In some manufacturing facilities, the constituents are combined and processed in a pelletizing extruder, which produces pellets of the new material. The pellets are then re-melted and formed into the final shape. Other manufacturers complete the finished part in a single step of mixing and extrusion.

 - Wikipedia