Wood Fiber: The ultimate engineering structural material: any takers?

[pvhramani]

Technologically, we have developed various engineering structural materials that excel in strength properties; nano materials, whiskers, tungsten and boron fibers, super cermets, carbon fibers ... et.all. We boast of nano-materials and whiskers that could have tensile strengths and moduli of over a million and fifty million MPa respectively. But strangely, many of our day-to-day engineered materials needs are yet to be answered. The matter is further complicated in the present "globalized" economy - what is accepted in an advanced nation such as the US may have no meaning in countries such as Zaire, Chad, Afghanistan, Bangladesh ... etc. Yet, these under-developed nations, whose population account for more than half of the 7 billion men and women in the world, do not have even the rudimentary means of shelter, clothing and food - forget about owning even a bicycle!

 

This writer has been wondering:Wood, which is a renewable resource could be a great general engineering structural material, if we could utilize the advantages of its renewable nature, low specific gravity, huge availability, and low cost.

 

Let us consider, as an example - the COCONUT Tree. On the basis of the natural average life span of sixty years, the world would have annually renewable coconut tree resources to an extent of not less than 100 million tons! The significance here is that, even if we do not voluntarily cut the tree, its life span being sixty years, we have so much "tree resources" naturally made available. And, in a world beset with the problems of CO2 and GHG increases through over exploitation of resources and energy, this is a materials engineering opportunity to be "grabbed".

 

From a technical angle, we may note that tree/ natural fibers such as those from coconut trees could even compete with some so-called super engineering structural materials - on the basis of "sp.strength", "equivalent weight rigidity", energy efficiency, availability and cost.

NOTE: Coconut tree is just one example. There are hundreds of other species that are available as renewable natural tree resources

 

What you think engineers. about this thought?

[insane_alien]

wood is only suited to it's particular niche in engineering materials. it will decay over time and eventually fail. is main use in construction is in low housing(three story max) and in temporary structures. and even in some of these cases it is unsuitable. wood is used because it is cheap. it is far from the best.

 

plastics made from biological materials would provide many more advantages than just using trees. this is because plastics are more versatile, they can be stronger, less flammable, more flexible, more conductive(use the structure of the house to distribute mains power?) less prone to decay over time and recyclable. plastics can also be used for other strucures, such as chemical plants, skyscraper cladding/reinforcement car manufacture, and so on.

 

they also lock up CO2 before you try that attack.

[Sisyphus]

Also, since when is wood construction not everywhere already?

[pvhramani]

Hello

 

I joined just today, and after I was really impressed at the superb quality of the web systems here, I also had a fast peep into some of the lively and knowledgeable discussions subjects. But am disappointed that here a subject that needs in depth understanding of materials engineering, Wood science, and knowledge about world materials scenario is being indulged in by relatively amateurish manner ... judging from the thread of discussions to my original presentation on wood fiber being considered as a specialty engineering material

 

Having said that it is NOT my intention here to discourage any one in discussing on such subjects. But, here is a serious SCIENCE forum... and it is expected that one would indulge in "talking" on a subject only based on individual experience

 

Thank you

[Phi for All]

I joined just today, and after I was really impressed at the superb quality of the web systems here, I also had a fast peep into some of the lively and knowledgeable discussions subjects.

Welcome.

But am disappointed that here a subject that needs in depth understanding of materials engineering, Wood science, and knowledge about world materials scenario is being indulged in by relatively amateurish manner ... judging from the thread of discussions to my original presentation on wood fiber being considered as a specialty engineering material

You've had two replies and I failed to find anything amateurish about either of them. Type V construction (wood-framed) is very common in the US and many people incorrectly assume wood is used extensively elsewhere as well.

 

You also failed to make any distinction between building with wood (or "sticks" like 2x4s) and wood fiber materials (which are completely different). This would be a great distinction for you to make.

Having said that it is NOT my intention here to discourage any one in discussing on such subjects. But, here is a serious SCIENCE forum... and it is expected that one would indulge in "talking" on a subject only based on individual experience

Calling the replies amateurish simply because they don't seem to agree with you is and ad hominem logical fallacy. I would suggest that you address the questions posed by detractors rather than trying to undermine their credibility by calling them amateurs.

Also, since when is wood construction not everywhere already

In many places wood is extremely expensive (Japan loves wood but doesn't really have the land to renew what they use). Many places also have climates where wood is impractical to use.

[pvhramani]

Although in its natural form these materials are prone to certain attacks, with the great advances in Engineering Composites, this problem is surmounted.

 

This writer has been working on certain Composites formulations, and on the basis of certain lab level tests, some very interesting observations have been made:

 

(1) Hybridized Wood/ Natural Fiber Polymer Composites (H-NFPC) could be in the sp.gr range of 0.75 to 1.15

(2) While the sp. tensile strength of steel is about 580 to 3, 000 (depending on mild steel, alloy steels, special steels etc), that of H-NFPC is about 1, 200 (the dimensional factors of sp.ten str are not mentioned here)

(3) A derived property such as Equivalent Weight Rigidity (in Kgf-cm2) is still more interesting: all steels = 175, 000; cast Al alloys = 1, 495, 000; cast Mg alloy = 3, 700, 000; S-Glass Epoxy = 2, 730, 000; C-Epoxy = 13, 975, 000; H-NFPC = 7, 550, 000.

 

Without going into the detailed subject matter on Derived properties etc, it is noted that in many structural applications the equivalent rigidity section in H-NFPC would weigh as low as about 30% of the steel section. This is a great advantage from the point of view of weight, cost, energy and various other manufacturing and usage aspects.

 

The idea of initiating this discussion is to create a forum of engineers who are interested in this, so that many more developments could be made, from the present infinitesimal level.

 

This writer wishes to hear more on these from other engineers who have done works in Wood/ Natural Fiber engineered products/ systems.

[Mr Skeptic]

Wood, and wood fibers, are already used extensively. Many houses in the US are made of wood, and wood is used extensively in paper. Indeed, our use of wood was causing such strain on the forests that we now grow special strains of fast-growing trees in tree farms for our paper needs. Not all trees are created equal, however, and slow growing hardwoods are most valued for wooden items. We use these hardwoods faster than they grow, which is a danger to the rain forests.

 

In places with coconut trees, the entire tree is used -- telephone poles and "logs" from the trunk, thached roofs from the leaves, edible fruit, fibers from the husks, fibers from inside the trunk, are all used.

 

Chemically, the cellulose can be used as a plastic-like substance. However, doing this is complicated. The lignin that binds cellulose and is the most common organic substance is still underutilized and frequently burned for energy.

 

As others have mentioned, wood is hardly ideal for many circumstances. It performs poorly under pressure, but is excellent for tension. It can rot and be worn away. It is flammable. It is complicated to work with. Valuable hardwoods are being used faster then they are replenished.

 

Also, why is this thread the top Google result for H-NFPC?

[pvhramani]

Hi

 

1. Let me begin with your last question:

 

"Also, why is this thread the top Google result for H-NFPC?"

 

In fact, as soon as I noted this observation from you, "googled" and saw the veracity of your statement! I too do not know how it reached there!

 

2. Your general statements about wood, its usage, its decay problems, and also about cellulose/ lignin have been noted. Without going deeper on the technicalities now itself, it is observed that almost all the "problem situations" of normal wood can be overcome in wood/ wood fiber based Composites. Also, about your apprehension of the "direct" use of wood: when wood is used without modification we tend to select only the so-called "best" wood materials, and that has been the cause of forest depletion and other "tree felling" related problems. More will come as this discussion progresses

 

3. The discussion here is on: wood/ wood fiber as a structural engineering material ... This suggests that wood/ wood fiber are to be considered in relation to other traditional Engineering structural materials such as: steel, aluminum, magnesium, plastics, ceramics, composites ... etc The following aspects are to be appreciated here:

 

(i) When we say wood/ wood fiber, hereafter, it pertains to the different material systems in wood, modified for COMPOSITES development. And we shall not be looking at the "regular" wood usage - which has stood the test of time for thousands of years (some one had asked: "since when is wood construction not everywhere already?")

(ii) As presented earlier, we shall discuss Natural Fiber Polymer Composites (NFPC), and Hybrid Natural Fiber Polymer Composites (H-NFPC), wherein the Wood/ Wood Fiber content shall take up to weight percentages of 40% to over 85% of the total composite weight

(iii) It is assumed that every one has a general idea of what a Composite is. Here again, without going into the full technicalities, it would be briefly noted that a composite is homogeneous mechanical combination of two or more material systems, in which at least one material is normally a BINDER. Wood itself is a natural Composite; Concrete is an artificial composite ...

 

4. Now, coming back to NFPC and H-NFPC, the differences are as below:

(i) NFPC has the main ingredient in the form of Wood fiber, and the binder ingredient is a Polymer that has affinity/ adhesion properties. The composite would also have certain special ingredients to impart decay resistance, fire-retardance, and so on

(ii) H-NFPC is hybrid NFPC that would have as hybrid ingredient, superior strength engineering fibers such as Glass Fiber, Carbon Fiber , Kevlar* Fiber ... This hybridization dramatically changes the strength properties, although at the sacrifice of increased cost.

(iii) We shall define Wood Fiber as wood elements having arbitrary length/ thickness ratio 100 or more; and the largest average thickness shall be arbitrarily restricted to 2.5 mm

---------------------------------------

*Kevlar is a DuPont invented High strength Fiber

----------------------------------------------------------

It may be noted that Wood fiber Polymer Composites (which can also include various other fibrous materials such as Flax, Banana Fiber, Pineapple fiber, Corn cob fiber ...), termed NFPC or H-NFPC are not new, and various engineers and technologists are working on these. The main theme of this writer is to discuss its potential as ALTERNATE ENGINEERING STRUCTURAL materials in place of steel/ aluminum/ plastics in auto body systems, boat/ ship building systems, building construction, and various engineering structural needs where the temperature conditions lie within 120 deg C

 

More to come later

[Skye]

The main problem with wood in alternate engineering structures is that it is not nearly as good at handling dynamic loads as other materials are, most notably steel.

[pvhramani]

It is here that Engineering comes in. For example, cement has ZERO tensile strength; but in reinforced concrete (and more so in "pre-stressed concrete), it is one of the BEST building construction materials. And more over, as already noted, we are not using wood in its original form, but as NFPC and H-NFPC. The hybridized version would be a superior engineering material. And, based on certain study results, these composites could soon enter engineering structural systems in a big way:-)

[insane_alien]

the composites still suck under dynamic loads. take a sheet of ply and a sheet of steel of equivalent strength and flex them an equal amount repeatedly. see which fails first. do the same with plastics. both the steel and the plastics wil outperform the ply and in some cases the plastic will outperform the steel.

[pvhramani]

You need to understand this - a repetition from an earlier thread here:

 

(1) Hybridized Wood/ Natural Fiber Polymer Composites (H-NFPC) could be in the sp.gr range of 0.75 to 1.15

(2) While the sp. tensile strength of steel is about 580 to 3, 000 (depending on mild steel, alloy steels, special steels etc), that of H-NFPC is about 1, 200 (the dimensional factors of sp.ten str are not mentioned here)

(3) A derived property such as Equivalent Weight Rigidity (in Kgf-cm2) is still more interesting: all steels = 175, 000; cast Al alloys = 1, 495, 000; cast Mg alloy = 3, 700, 000; S-Glass Epoxy = 2, 730, 000; C-Epoxy = 13, 975, 000; H-NFPC = 7, 550, 000.

 

If you are not able to understand these... please ask... I would help by giving a link for you to study these fundamental engineering properties of materials. Here you will find that NFPC/ H-NFPC based on wood/ natural fibers would be far superior to steel in RIGIDITY Modulus

[insane_alien]

i understand them fine. but that is hardly a comprehensive list is it. and rigidity is not always a desirable property in construction. sometimes flexing is best and then there is the whole strength/volume thing.

[John Cuthber]

I'm sat on a wooden chair, held up by wooden floorboards. The roof that keeps the rain off me is slate (which is water proof) but held up by wooden bars. Similarly, the walls are stone because it's not going to rot any time soon. The house is a hundred years old and if I'm careful (ie I don't burn it down) it will outlast me.The computer in front of me is on a wooden table.

I'm wearing a cotton shirt and jeans.

OK, part of the reason that's a whole lot of cellulose is that it's cheap and easy to get, but surely part of it is that it's good at its job.

What engineering material would you sugest I made the floor from? (please note Imight want to lift bits of it to lay power cables etc and I might want to fix carpets to it. Even with the carpets, I still want the stuff to be a fairly good thermal insulator. It needs to be strong enough that my book collection doesn't fall through the floor. I can put up with it flexing slightly under my weight but not much more than timber does. This should give it enogh elasticity to cope with thermal expansion as the house heats and cools without trying to bend the walls.

Also, I want to be able to repair it if it gets damaged - preferably myself without expensive specialised tools.

 

I think timber is pretty good stuff.

 

BTW, re the question about bending a piece of wood back and to repeatedly. This experiment has been done with trees for thousands of years and with dead wood for hundreds as timber framed buildings have swung in the wind. It seems to do well enough.

[MrMongoose]

By far the main difficulty with wood is the fact that it only comes in one shape and you cant melt it down and remould it

[insane_alien]

but remember, we're talking about wood composites here not planks of wood.

 

think of plyboard or fiberboard here. composites CAN be giver wierd shapes but they're not as god at it as plastics and remolding isn't really viable.

[John Cuthber]

Remolding wood is called composting and planting seeds. It's not quick, but it's easy.

Of couse there's always steaming the stuff and bending it too.

Anyway, who needs to mold it to funny shapes?

http://www.jthep-antiquities.co.uk/Bespoke%20Work/Examples/Wooden%20chain/Wooden%20chain.htm

[Mr Skeptic]

Remolding wood is called composting and planting seeds. It's not quick, but it's easy.

Of couse there's always steaming the stuff and bending it too.

Anyway, who needs to mold it to funny shapes?

http://www.jthep-antiquities.co.uk/Bespoke%20Work/Examples/Wooden%20chain/Wooden%20chain.htm

 

Do you know how painful it is to carve wood into a chain? With iron or plastic it is much easier.

 

But with wood you can do this, though it will take a while...

[Mr Skeptic]

Newscientist has an article about using bamboo composite as a replacement for iron/concrete for bridge building. Strips of bamboo are glued into timber-like shapes.

[Norman Albers]

How will it be after several decades of exposure and stress? I don't think it's strange because all this is evolving indeed. Several things including plastics are being used as inclusions in concrete and what are their lifetimes?

[vampares]

Wood is relatively expensive. Cinder block and prefabricated concrete or on-site concrete molds are much more reliable and cost about the same amount.

 

Urbanization ultimately relied on redbrick. The brick has become one of the most essential elements to modern Anglo-Saxon society. It doesn't burn, it doesn't weather and need replacing, it is a poor acoustical conductor -- this is real value. Redbrick was used in many early urban skyscrapers.

 

The down side of brick is that is becomes ugly and monotonous. Wood structures have an airy feel. American suburbs are really like upscale trailer parks.

 

Steal has taken the place of the wood frame. Gypsum board is a little bit more rugged than it was and no longer needs the supports. Most homes and small buildings have iron pillars and I-beams doing the weight bearing.

 

The third world consideration is a little bit more complicated than just woods availability. Most of these resources are consumed as fuel, not as structural material. They use things like oil drums and corrugated steal for this (see Crackhouse).

 

I would like to see someone come up with a meaningful use for the pasture grass that most American homes are surrounded with (don't say goats).

[Norman Albers]

I know a straw bale house here in southern Oregon, and it has almost no heating or cooling needs.

[CaptainPanic]

wood is only suited to it's particular niche in engineering materials. it will decay over time and eventually fail. is main use in construction is in low housing(three story max) and in temporary structures. and even in some of these cases it is unsuitable. wood is used because it is cheap. it is far from the best.

 

In the Netherlands, many old houses are build on wooden poles, drilled into the soil (for the foundation). Also, the roofs are usually suppored by wooden beams. Some, like in Amsterdam, are 400 years old. I'd say this shows it is at least durable. And you can go up 5 stories.

 

I agree that skyscrapers will not be made of wood. I also agree it's not the strongest, but I disagree with the words "it is far from the best.". It really depends on the criteria you use. I think "the best" can mean the best price/quality ratio (economics), or the best material properties. These are obviously not the same.

 

Can I say that this thread is very ugly because of all the different fonts and fontsizes? It isn't inviting me to read.

[insane_alien]

i didn't say a would supported structure couldn't last centuries. it is just that most won't. in a town near me there are 3 quite new buildings(5 years old for the oldest one) condemed because their wooden frames have rotted through.

 

an extra 2 stories is still kind of low.

 

as for best i thought is was clear from the context that i was not meaning quality over price but merely quality. even with quality over price it is mediocre.

 

unless the quality you are looking for is 'wood' then it would be best.

[Mr Skeptic]

I know a straw bale house here in southern Oregon, and it has almost no heating or cooling needs.

 

Don't they tend to have some problems with insects and molds, and god help you if it gets wet