Metals

Woods

Almost any type of wood can be used to build furniture, but some woods have always been favored for their beauty, durability, and workability. Before 1900, most woods made for furniture were made out of walnut, oak, mahogany, rosewood, fruitwoods, and rare wood veneers. The preferred furniture woods were easily available, so less attractive or durable woods were used only for hidden parts inside a piece. For this reason, pre-1900 furniture is almost always worth restoring.

As these preferred woods have become rarer and more expensive today, most furniture is made with ash, pine, gum, and poplar. Pine, fir, and other inexpensive woods are used for hidden parts. The rare woods are used only for very good furniture.

Being able to identify the type of wood used for your furniture can help you determine its real value. Wood identification can sometimes be the deciding factor when you aren't sure if a piece is worth refinishing or if it should be thrown away.

The woods that are fashioned into furniture fall into three categories:

1. Hardwoods

2. Softwoods

3. Composites

The term 'hardwood' or 'softwood' is misleading. Hardwoods aren't necessarily harder, denser material. For example, balsa wood is one of the lightest, least dense woods there is, and it's considered a hardwood. Technically, lumber is classified based on how the tree reproduces. As a general rule, though, softwood trees are evergreen year round while the hardwoods create the gorgeous autumn foliage that we all love so much.

Hardwoods are considered the highest quality and are the most expensive. Their natural colours vary from the darkest woods to the lightest ones and can be stained or painted for even more variety. Hardwood furniture is least likely to warp or bend.





Softwoods are less expensive than hardwoods, but they require extra care. Because they are less durable, it's much easier to scratch or dent softwood furniture. In addition, they often don't have the beautiful grains of a hardwood, and therefore don't tarnish as beautifully.


Composites are the cheapest form of wood and are literally manufactured, rather than grown. Three types of Composites are Plywood, Particle board, Hardboard and MDF.

1. Plywood: multiple layers of thin wooden sheets are glued together and pressed. Plywood is strong and resists swelling, shrinking and warping. There is some furniture made directly from plywood, but generally it is only used as a support when integrated into furniture.

2. Particle board: sawdust and small wood chips are mixed with glue or resin which is then shaped and pressure treated. When used for inexpensive furniture, particle board is usually covered with laminate or veneer. This is necessary because particle board splits easily and the laminate prevents splitting.

3. Hardboard: is made like particle board but it's placed under higher pressure so it's stronger.

4. MDF or Medium Density Fiberboard: wood particles are bonded with resin and compressed. It is harder than particle board or hardboard, and can be cut like plywood although it isn't as strong as plywood. Some MDF is covered with melamine which is a durable plastic in a variety of colours. The exposed edges of MDF are rough and need covering with a decorative material.


Technically, furniture made from all of these wood products is "real" wood furniture, even the composites. Prices and quality range from the hardwoods down to the composites. The higher you go up the range, the more you can expect to pay for your wood furniture. The good part is that with proper care hardwood furniture will last for decades or even generations. If you can afford it, always choose hardwood furniture.

http://tlc.howstuffworks.com/home/guide-to-furniture-woods-ga.htm

http://ezinearticles.com/?3-Kinds-Of-Wood-Used-In-Real-Wood-Furniture&id=61650

Composite Materials

In an advanced society like ours we all depend on composite materials in some aspect of our lives. Fibreglass, developed in the late 1940s, was the first modern composite and is still the most common. It makes up about 65 per cent of all the composites produced today and is used for boat hulls, surfboards, sporting goods, swimming pool linings, building panels and car bodies.

Most composites are made up of just two materials. One material (the matrix or binder) surrounds and binds together a group of threads or remains of a much stronger material (the reinforcementIn fibreglass, the reinforcement is provided by fine threads or fibres of glass, often woven into a sort of cloth, and the matrix is a plastic.

The threads of glass in fibreglass are very strong under tension but they are also brittle and will snap if bent sharply. The matrix not only holds the fibres together, it also protects them from damage by sharing any stress among them. The matrix is soft enough to be shaped with tools, and can be softened to allow repairs to be made. It is also quite light, which is an advantage in many applications.

Over recent decades many new composites have been developed, some with very valuable properties. By carefully choosing the reinforcement, the matrix, and the manufacturing process that brings them together, engineers can modify the properties to meet specific requirements. They can, for example, make the composite sheet very strong in one direction by aligning the fibres that way, but weaker in another direction where strength is not so important. They can also select properties such as resistance to heat, chemicals, and weathering by choosing an appropriate matrix material.

Making an object from a composite material usually involves some form of mould. The reinforcing material is first placed in the mould and then semi-liquid matrix material is sprayed or pumped in to form the object. Pressure may be applied to force out any air bubbles, and the mould is then heated to make the matrix set solid.

The moulding process is often done by hand, but automatic processing by machines is becoming more common. One of the new methods is called pultrusion (a term derived from the words 'pull' and 'extrusion'). This process is ideal for manufacturing products that are straight and have a constant cross section, such as bridge beams.

In many thin structures with complex shapes, such as curved panels, the composite structure is built up by applying sheets of woven fibre reinforcement, saturated with the plastic matrix material, over an appropriately shaped base mould. When the panel has been built to an appropriate thickness, the matrix material is then cured.

The greatest advantage of composite materials is strength and firmness combined with lightness. By choosing an appropriate combination of reinforcement and matrix material, manufacturers can produce properties that exactly fit the requirements for a particular structure for a particular purpose.

http://www.science.org.au/nova/059/059key.htm