Lesson video

Hello, welcome to Design and Technology lesson.

My name is Mrs. Conway, and I'll be guiding you through your learning today.

So today's lesson outcome is, I can explain how timber material properties can be enhanced.

And these are our keywords: properties, combine, modify, reinforce, and structural integrity.

We'll go through each one of these as we work through the lesson.

So the first thing we're going to look at then is combining materials.

Now, materials don't always have the perfect properties for the job we want them to do.

Sometimes they're too weak, too flexible, not hard-wearing enough, or just can't handle heat or moisture.

And by enhancing material properties, we can make products stronger and last longer, improve safety and performance, and also allow innovation in design and function.

So it's a good thing to enhance material properties.

Now, properties are words used to describe how a material appears, such as physical characteristic, or how it behaves when worked, so working or mechanical properties.

Now, there are three ways that a material's properties can be enhanced.

Combining, which is joining together.

Modifying, which is changing.

And reinforcing, which is making it stronger.

Okay, which three methods are used to enhance material properties? A, compare, model, reinforce.

B, combine, manufacture, repeat.

C, combine, modify, reinforce.

Or D, compare, modify, and reuse.

Okay, pause the video here.

Just take a moment to think about your answer.

And the correct answer was C.

So the three methods that are used to enhance material properties are combine, modify, and reinforce.

Well done if you got that right.

Now, composites are materials that are made by combining.

Now, we combine a matrix, which is a binder, and reinforcement, and that's used for strength, and that creates a material with improved overall properties.

So an example of this or an example of a composite is a chocolate chip cookie.

Now, the dough is the matrix, that's the binder, and the chips are the reinforcement, so they are the added strength.

Another example is also a lava or layer cake where the reinforcement is encapsulated, in the case of the lava cake, or layered through the matrix, in the case of the layered cake.

This image shows Oriented Strand Board.

The matrix is resin adhesive, and the reinforcement are strands of soft wood timber.

This results in a timber board of uniform strength and is used widely in construction for that reason.

The softer strands are mixed with resin and compressed with high pressure.

Other examples then include Cement Bonded Particle Board or CBPB, and that's made from wood chips, which are the reinforcement, and Portland cement, which is the matrix.

Now, this results in a fire resistant material and can be used for building panels and cladding, and it looks a little bit like a chipboard.

Wood Plastic Composite or WPC is made from wood fibres, which is the reinforcement, and thermoplastic polymers, which is matrix.

And this results in a water-resistant, low-maintenance material, and can be used for things such as like decking and fencing, so extremely useful material.

Okay, quick check for understanding then.

In a composite material, what is the role of the reinforcement? Is it A, to hold the structure together? B, to give strength or other useful properties? C, to add as a decorative layer? Or D, to make the material more flexible? Pause the video here.

Just take a moment to think about your answer.

And the correct answer was B.

So the role of the reinforcement is to give strength or other useful properties.

Now, sometimes composite materials don't include a matrix and a reinforcement, but instead they are simply laminated.

And laminated is when they're layered together.

So engineered wood consists of a solid wood top and a plywood core.

The plywood prevents any warping or any shrinkage, while the solid wood top is really aesthetically pleasing.

Another example are veneers.

Not veneers for teeth, these are kind of different, but similar kind of concept.

Veneers are thin surface layers made from real wood paper, or vinyl, and they're laminated onto manufactured boards to add strength and protection, as well as, again, add that visual appeal or improve the aesthetics of the product.

The word ply means layer, and you may have heard that word before, and I've just mentioned plywood, so it's already used in there.

Now, plywood is made of several layers of wood veneer laminated together.

The veneer layers are positioned with the grain adjacent to each other at 90 degrees.

So one layer and then the next layer going 90 degrees to the next, and then again it continues.

Now, this prevents warping and provides uniform strength and stability in all directions, making it useful for things such as furniture.

So here's an example, you can see in that diagram, the bottom layer is going one direction, the middle layer or the next layer is going 90 degrees.

You can just see the grain lines going 90 degrees to the bottom layer.

The layer above or the top layer is then again going 90 degrees to that second layer.

So each time, 90 degrees is twisted as it's layered up.

So it alternates between each layer.

Okay, quick check for understanding then.

Which property is improved by using plywood instead of solid timber? Is it A, stability and resistance to warping? B, electrical conductivity? C, transparency? Or D, thermal insulation? Pause the video here.

Just take a moment to think about your answer again.

And the correct answer, it was A.

Okay, so using plywood instead of a solid timber improves the stability and also the resistance to warping.

It's gonna be over to you now to have a go at a few tasks.

The first task then, I'd like you to explain what a timber-based composite is, referring to the terms matrix and reinforcement in your answer.

So that key vocabulary of matrix and reinforcement must be included.

The second task then, I'd like you to explain why plywood is better suited for some furniture than solid timber.

And lastly, I'd like you to describe two benefits of using composite materials, and I'd like you to use examples in your answer.

Okay, it's gonna be over to you now then.

So pause the video here to have a go at these tasks, and good luck.

Okay, hope you got on okay with those tasks.

I'm gonna give you some example answers now just for you to combine yours too.

So the first task then was to explain what a timber-based composite is, referring to the terms matrix and reinforcement in your answer.

So the example answer says, "A timber-based composite is a material made by combining a polymer matrix, the binder, with reinforcement, such as soft wood fibres, to improve strength and performance.

The matrix holds the structure together, whilst the reinforcement adds strength and stiffness." The second task then, explain why plywood is better suited for some furniture than solid timber.

"Plywood resists warping and is more stable than solid timber.

It is strong due to its cross-laminated structure, making it ideal for furniture." So again, just compare your answers to mine.

Have you included enough detail in there? In the first question, did you make sure to use the words matrix and reinforcement in your answer? The third task then, I asked you to describe two benefits of using composite materials, and I also asked you to use examples in your answer.

So the example answer says, "Fire-resistant, e.

g.

CBPB is used for cladding on buildings because the addition of cement prevents the catch and spread of fire.

And the other benefit, resistant to corrosion and rot.

So e.

g.

WPC, and WPC is ideal for outdoor decking as it doesn't splinter or decay like natural wood.

Okay, again, just compare yours to mine.

Did you remember to use examples in your answer and have you explained those two benefits clearly? Okay, next, we're gonna look at the modifying of materials.

Modifying material means changing its structure or composition, which is what it's made from, to improve how it performs. And the changes usually take place at a molecular level and include heat treatments, chemical treatments, and structural modification.

Now, surprisingly, heat treatment can be used to alter timber properties.

Yakisugi is a traditional Japanese method of preserving timber, and it literally means burnt cedar and involves charring the wood surface to leave a layer of carbon.

And this layer is resistant to decay, water, insects, and even fire.

Thermally-modified wood is heated in a controlled environment to make it more stable and resistant to decay.

It's also moisture-resistant, which makes it ideal for things such as saunas.

Steam bending is another method that uses heat.

So steam bending is a method where wood is heated with steam to make it soft and bendable.

The heat and moisture loosen the wood fibres, so it can be shaped without snapping.

Steam-bent timber is commonly used in curved furniture, as well as musical instruments, or architectural features, as well as things like skateboards as well.

The steamed timber is left to cool and dry in a clamped jig where it will permanently take on its bent form.

Now, timber-based materials can have chemical treatments to enhance their properties.

They are normally pressure-treated so that the chemicals can penetrate deep into the wood fibres.

So some examples of chemical treatments then to enhance properties.

Now, timber used outdoors is usually treated with preservatives to prevent rot and insect attacks, so things such as your fencing in your garden.

Fire retardants slow the spread of fire and are used in timber-based public buildings such as holiday cabins.

And timber garden furniture can also be treated with water appellants to increase its lifespan as well.

Okay, quick check for understanding on chemical treating then.

What is the purpose of chemically treating timber? A, to improve the colour and texture of the timber.

B, to reduce the cost of timber products.

C, to enhance the timber's resistance to decay, insect, and fire.

Or D, to increase the timber's flexibility and smoothness.

Pause the video here.

Just take a moment to think about your answer.

And the correct answer, it was C.

So the purpose of chemically treating timber is to enhance the timber's resistance to decay, insects, and fire.

Well done if you got that right.

Kerfing is a structural modification technique where a series of closely spaced cuts or kerfs are made partially through a piece of timber to allow it to bend or curve more easily.

So here is an example just to explain that.

Those are the kerfs you can see there.

Now, kerfs are commonly used in curved furniture, musical instruments, or architectural features.

If, for example, you have a guitar at home and you look inside, I'm talking more of a classical guitar and acoustic guitar, and you look inside, you can usually see some example of kerfs.

Laminating timber can also create curved pieces as well.

So thin strips or veneers are glued together and clamped to a bending jig.

Once dry, the timber strips or veneers hold its new shape.

So glue is applied to a timber veneer, then the veneers are layered and clamped in a jig, and then the veneers hold their shape once dry, a bit like the steam bending does.

Okay, it's going to be over to you now.

The first thing I'd like you to do is to choose one heat treatment technique for timber and explain A, how it's applied, and B, how it improves timber's properties.

The second task, I'd like you to name a chemical treatment and explain, again, A, how it is applied, and B, how it improves timber's properties.

And the last task then, I'd like you to explain the difference between kerfing and laminating as methods of bending timber.

Please give one use for each method.

Okay.

Feel free to pause the video here to have a go at this task and good luck.

Okay, let's have a little look at some example answers.

So just compare yours to the ones in front of you.

So the first thing I asked you to do then was to choose one heat treatment technique for timber and explain A, how it's applied, and B, how it improves the timber's properties.

So the example answer says, "One heat treatment technique for timber is Yakisugi, a traditional Japanese method.

The surface of the timber is charred using controlled flames.

Charring the surface creates a carbon layer that makes the wood more resistant to water, insects, and rot.

It also enhances fire resistance and the timber's lifespan when used for exterior applications like cladding.

Additionally, it provides a distinctive aesthetic finish." As I explained, just compare your answer to mine and just check have you included how it's applied, as well as how it improves the timber's properties in your answer.

Your second task then was to name a chemical treatment and explain A, how it's applied, and B, how it improves timber's properties.

So let's look again at the example answer here.

"One chemical treatment for timber is the use of preservatives.

The timber is placed in a pressure treatment chamber, where the preservative is forced deep into the wood fibres under high pressure." So here you can see the answer has been done for A, how it is applied.

The second part of the answer then tackles B, how it improves the timber's properties.

"This treatment protects the timber from fungal decay, insect attack, and moisture, making it more suitable for outdoor use, such as in fencing, decking, or garden furniture." Again, just compare your answer to this one and double check that you've managed to answer both A and B parts of the question.

And lastly then, the third task was to explain the difference between kerfing and laminating as methods of bending timber.

And I asked you to give one use for each method.

So let's look at the example answer.

"Kerfing involves making a series of shallow cuts or kerfs on one side of a piece of timber to allow it to bend.

The cuts reduces stiffness so the wood can flex without snapping.

It's often used for simple, gentle curves in thicker wood, such as curved panels in furniture.

And laminating involves glueing together several thin layers or strips of wood and pressing them into a curved shape using a jig.

Once the glue dries, the shape is held permanently.

And this method is used for stronger, more complex curves, like in bent chair arms or laminated beams." So just check if you've really in enough detail explained the difference between the kerfing and the laminating, and also if you've included an example or a use for each one of those methods.

So lastly then, we're going to look at these keywords structural integrity.

Now, materials can be reinforced to enhance their properties, and we've already looked at that during this lesson.

And reinforcement involves adding an element or altering the structure of a material to improve its performance under stress.

Reinforcement techniques can be applied to a variety of materials, including timbers, polymers, papers and boards, textiles, and metals.

So a range of different types of materials all can be reinforced in some way to improve their structural integrity.

Okay, quick check for understanding on reinforcement then.

Why might materials need to be reinforced? A, it improves aesthetics.

B, to make them stronger and last longer.

C, to reduce costs for the consumer.

Or D, it makes them more environmentally friendly.

Pause the video here.

Just take a moment to think about your answer.

And the correct answer, it was B.

So materials need to be reinforced to make them stronger and last longer.

Now, reinforcing materials improves their structural integrity, and structural integrity refers to how well something stays together and holds up without breaking.

For timbers, the techniques used to ensure structural integrity are particularly prevalent in things such as frame structures that require bearing of load, so such as construction of buildings.

A timber knot is a spot where a branch used to grow from a tree.

In structural applications, it is a weak point in the timber because it can split and crack very easily.

Think about if you've ever used a piece of wood in the work that you've been doing or a piece of timber such as pine.

If you've come across that knot, you may have had some kind of splitting around that.

A knot plug or Dutchman patch is when a damaged knot is removed and replaced with a solid piece of timber, sometimes another knot that's actually undamaged, and that helps to add strength, but keeps that traditional kind of natural look.

Working with knots is generally avoided because the structural integrity of the timber does become compromised.

So this is one way around it, a knot plug is one way around it, but generally it's kind of avoided.

So what does structural integrity refer to in materials and structures? A, the ability of a structure to maintain its shape under normal conditions without breaking.

B, the aesthetic appearance of a structure.

C, the ability of a structure to resist environmental changes like temperature and moisture.

Or D, the cost-effectiveness of building a structure.

Okay, pause the video here to have a quick think about your answer.

And the correct answer was A.

So structural integrity refers to in materials and structures the ability of a structure to maintain its shape under normal conditions without breaking.

Now, interlocking joints are shaped timber connections that fit together to create stronger joints without relying solely on nails or screws.

There is also an increase in the surface available for using an adhesive if required as well.

And there are many different types of interlocking joints that are often used in furniture and timber frames.

So an example, a cone joint.

Now, these are often used in things such as decorative boxes and they use interlocking teeth and has an increased surface area available for glueing because of those interlocking teeth.

Another example would be fluted dowels in dowel joints.

They're commonly found in flat-pack furniture because their flutes or their little ridges on it basically help to grip into a hole without adhesive.

Adhesive can be added, but those flutes can work without it.

Now, joining timber pieces to make a new material is not only cost efficient and environmentally friendly, but can also actually help it become more sturdy.

Glulam is an engineered timber made by glueing layers of timber together with the grain running in the same direction.

It is often used for roofing beams where high strength is needed over a really long distance.

Now, finger joints use long interlocking fingers to join timbers end-to-end and extend its length also.

Okay, which of the following statements best explains why interlocking joints are useful in timber construction? A, they only work with nails or screws to hold timber together.

B, they create strong connections by fitting together and may increase glue surface area as well.

C, they are designed mainly for metal furniture.

Or D, they rely entirely on fluted dowels and adhesives.

Pause the video here just to take a moment to think about your answer.

And the correct answer was B.

So they create strong connections by fitting together and may also increase glue surface area.

Now, there are several types of reinforcement methods that are used in timber structures to improve their strength and also their stability.

So corner braces are diagonal pieces added between vertical and horizontal lengths to keep structures square.

And you will have seen these and even may have used some of these in your products without really thinking or knowing the name of them before.

So these are called corner braces.

Tie bars connect two structural elements like walls across an open space to prevent collapsing.

And you can see those examples in the image there.

Now, notice how these beams create triangles.

Now, triangle is one of the strongest shapes that do not buckle under pressure.

Now, this method of reinforcement is called triangulation.

Now, the addition of metal plates can also help with connecting timber and provide structural strength as well.

Corner plates strengthen right-angle joints and are attached with screws.

T-plates also do the same thing.

Now, T-plates support T-shaped connections and they help to prevent movement and are also attached with screws.

Okay, it's gonna be over to you now to complete a few more tasks and these are your last tasks of the lesson.

So number one, what is a knot in timber and why is it considered a weak point in structural applications? The second task, I'd like you to describe two different ways timber can be reinforced to improve its structural integrity.

And lastly, I'd like you to explain how interlocking joints and engineered timber products improve the performance of timber structures.

And I'd like you to give one example of each.

Okay, it's gonna be over to you now, so good luck with this task.

Pause the video here to have a go.

Let's have a little look at the example answers then just for you to compare your answers to.

So the first thing I asked you to do then is answer this question, what is a knot in timber and why is it considered a weak point in structural applications? So the answer here is, "A knot is where a branch grew from the tree.

It's a weak point because it can easily split or crack under stress, reducing the timber's strength." The second task then, I asked you to describe two different ways timber can be reinforced to improve its structural integrity.

And the answer includes here, "Triangulation involves forming triangular shapes in the structure, which are very stable and resist movement or collapse.

Triangles are the strongest shape because it doesn't buckle easily under pressure.

Also using metal corner or T-plates strengthens joints by securely connecting timber lengths and providing structural support." Just compare your answers to the examples there.

Have you described two different ways that timber can be reinforced? And with the knot, have you actually explained why it's considered a weak point? And the last one then, I asked you to explain how interlocking joints and engineered timber products improve the performance of timber structures.

And I also asked you to give one example of each.

So the first example here, "Interlocking joints improve performance by fitting timber pieces together in a way that increases strength without needing lots of nails or screws.

They also provide more surface area for adhesive.

So for example, a comb joint has interlocking teeth that makes box corners stronger." And the other example I gave here was engineered timber.

"So engineered timber, like glulam, is made from glueing layers of wood with the grain in the same direction.

And this makes it stronger and suitable for long spans, such as roof beams where solid timber might bend or break." Again, just compare your answer to mine, check that you've given an example for each of those.

So let's summarise today's lesson.

Today, we've been looking at enhancing the properties of timbers.

Now, combining materials creates improved properties compared to the individual material alone.

So if we're combining materials, the reason we're doing it, we're trying to improve the properties of those materials.

Material properties can be modified with the use of heat and also additives.

And reinforcing techniques can improve material performance as well.

Well done for all of your hard work today.

Thank you so much for joining me and I will see you soon.