Why Is Honeycomb Used?

Honeycomb is lighter in weight and stronger in strength. Hence in certain applications when this criteria is a must, like in aeroplanes, these are used.

Also, in aero engine turbine, such honeycomb sections are used, for sealing of hot gases leakage between the tips of blades and casing. These blades do get longer (due to creep and the expansion) somewhat, when in operation due to very high temperatures of combustion gases passing through the turbine. Since the honeycomb section is easy to work with, an the extra clearance is created, without damage, when casing and blade tips rubbing take place. Here, the honeycomb material is suitable for high temperature application.

There may be more such applications, but the above is just one of them.

Chittaranian that is utter twaddle. You imply that you know more than your message imparts. Confusion is not equal to knowledge. Either be succinct and factual or stay at home.

Big Bad Bob

Chittaranian that is utter twaddle.

Big Bad Bob. I think you are confusing lack of command of English with lack of understanding of the subject. Otherwise you are illustrating your own lack of understanding of the subject. Every turbine engine, except a few made in Russia, uses high temperature alloy honeycomb to form seals which reduce pressure loss past the tips of the rotor and stator blades. Honeycomb is also used for similar purposes in some rocket engines and the new pulse detonation engines for multi-mach speeds.

Dick

Drawing upon my extensive command of the english language, I said nothing.

"can any one why honeycomb is used and what are its advantages"

It has the proper configuration for bees to build the honey comb on to store honey and to raise the larve for future generations of honey bees!

honeycomb is used where you want strength and rigidity with low weight.

each cell is a regular hexagon and you can find them in different materials, cell sizes and thicknesses to suit the application.

drill down into these searches

http://www.google.com/search?hl=en&q=honeycomb+%2Bmetal&btnG=Google+Search

http://www.google.com/search?hl=en&q=honeycomb+%2Bplastic&btnG=Search

http://www.google.com/search?hl=en&q=honeycomb+%2Bwood&btnG=Search

As chittaranjan said, honeycomb is stronger than the same amount of material in a solid sheet, and much lighter than the same volume of solid material.

The honeycomb used for turbine airseals is much softer than the turbine blades themselves, so can be crushed by the turbine blades such that the honeycomb just fills the gap between the blade tips and the inside of the turbine housing at operating temperature. The honeycomb cells point radially inward, so the gas flow they are restricting is essentially perpendicular to the cell axes. Turbine blades also commonly have knife edges that cut grooves in the honeycomb, thus creating a more complex path for gas leakage and therefore a better seal. The honeycomb performs the same function for turbine engines as piston rings do for reciprocating engines.

If a skin is added to the top and bottom surfaces of the honeycomb (the ends of the cells), the resulting sandwich is extremely light and strong. Such material can be made of plastics, composites, metals, etc. For metal sandwiches, the method of attaching the honeycomb to the skins is critical to the strength of the sandwich. Unfortunately, true metal honeycomb is very slow and therefore expensive to manufacture, so it is generally only used where its strength-to-weight ratio is very valuable, as in aircraft and spacecraft.

Honeycomb-like sandwiches are being developed that are cheaper to manufacture, and still have much (but not all) of the advantages of true honeycomb sandwiches.

Hi, Guest!

In catalytic substrates, honeycombed ceramics are used because they can be washed several times with various catalysts, which deposit and adhere in random molecular bunches throughout the length of the honeycombs. The honeycombs force the entering exhaust effluent to divide up into smaller processable parcels, and the randomness of catalytic deposits within them assures a more thorough catalytic process, because it can take place over and over depending on the random order and size of catalytic deposits.

Mark

Honeycomb ceramic substrates provide more rodium (or pladium) coated surface area exposure to exhaust gases and helps the thermal transfer.

Hi abhi,

Honeycomb structures are mainly used in aeroplane industry due to its light weight and highest strength characteristics. Other applications included tennis racket, ski board, speed boat and formula one racing car's protective nose cone etc. Recently, many researchers try to use honeycomb composites for personal protective equipments and car manufacturing.

KCDYU

Hi Abhi,

I would just like to add honeycomb intake filters are used a lot in many low-speed wind tunnels for "streamlining" the airflow inside the test chamber.

Regards,

CLoud

Can you be more specific? Did you mean beeswax? It is used in toilets because it is sticky and compresses to form a good seal to keep out the sewer gases.

I checked with my local apiary and, yes, bees do have indoor plumbing. hehehe. It has been interesting reading this thread and seeing all the assumptions about what the OP might possibly have meant by "honeycomb."

europium - new avatar? Nice!

We used honeycomb cardboard under vehicles we were rigging for airdrop - the vehicle sat atop a designated amount and shape of the material and was then secured to a heavy pallet. When the pallet hit the ground the vehicle bounced and compressed the honeycomb, which left a lot of the rigging material lose - then we could get the vehicle off of the rigged mess pretty quickly.

Thanks, Sleddriver! I spotted that pic when doing a Google image search for something else. You know, I've wondered sometimes how they rig vehicles for airdrop so that they won't get trashed when hitting the ground. Cardboard huh? Cool! Amazing what you can make out of what is, basically, good ol' fashioned paper. But a question for you: how to guarantee that the vehicle will plop straight down? Or is the cardboard placed around the vehicle in such a way as to protect it in case the load strikes at an oblique angle? I'm also curious about the gee-forces experienced on impact. These loads are moving at, what, 10-15 feet per second? And they stop within the crush-distance of the cardboard which is, what, maybe 12-18 inches? I'm just guessing at all this, of course.

There is a nice film somewhere on the net, showing how wrong this vehicle dropping can go.

The cardboard takes the impact energy by deforming.

This principle is used in several applications, there are even inter-university games: how high can we drop something before it breaks. Eggs are mostly used.

I think, honeycomb has minimum periphery to area (volume) ratio and by using honeycomb shape a planar surface can be covered without any gap.

The honeycomb, being heaxagonal columns on a triangular matrix, is an ideal way of packing volumes into a small space, as are rectangular boxes.

So why has the cylindrical food can become so prevalent? Discuss...

Waaaal, PeeDubeeya:

I b'lieve it's coz the cans contain all diffr'nt kinds o' feud, but thu other thang kin only holt hony.

Course that there's only a pers'nal ho-pinion.

Yore Pal,

Cousin Mark "weak-eyes" Handyman

Cans must be round! I just found myself a decent circular can opener.

As i read through the mails I see a lot of nice answers but now directly answering your question:

Why do they use honeycomb?

The honeycomb you are referring to is the structural element usage.

The name is in fact a structure: the honeycomb is in between two plates, which in theory are not strong enough to take the load as they bend. By separating the two plates with a lightweight structure the stiffness of the system rises enormously, stiffness goes of with the power of 3 in thickness of a plate.

It is used in the walls of planes, doors, floors, panels for buildings, ... everywhere you want a light structure that keeps its shape.

In doors the honeycomb itself is paper, lined with some mm of wood. The result is a lightweight stiff structure.

Why using the honeycomb system: to save material for cost or weight reasons. A solid plate would have been much stronger, but the plane would not take that much passengers.

You can make it yourself: start sparing the toilet rolls and insist on having the same make. when you have some your glue them standing on a piece of cardboard, also glue the sides. on top you glue a sheet of cardboard to. The result is a plate that can take a lot of weight, to astonish you grandmother.

Gwen

I did, and my grandmother was very astonished. Thanks.

Mark

PS. I'd ask you if you have any ideas on how to astonish my wife, but I won't let you go there!

Depending on the time of day you could try to use honeycomb too.

Ask a bee, sounds like you are talking Beespeake, try explaining your use or question...

Have you ever noticed that ice cream cones have a honeycomb bottom too? Oh, and so do ladles for carrying molten steel!

Everyone seems so willing to complicate matters! Honeycomb is used to hold the honey. Jeez!

And on that note Big Bad Bob puts his five cents in again. Dick - I am fairly familiar with turbine seals - I am one of those cursed beings who's lot for the past two and a half decades has been to design the mechanical components of very high speed delivery platforms, albeit that few still use rotational devices for any application other than torque dissolution (which is what the fancy farts call it when we stop things breaking because their rotational acceleration exceeds permitted constraints) . I'd much rather be working with the birds and the bees some days.

However the worst thing to hit engineers and engineering is this acceptance of "guru-talk" where we have semi (English) literate wannabees trying to teach well-meaning youngsters something about which the former has little or no knowledge. As I said - its better to stay at home. I live in a Country where we daily see class-distinctive mentalities destroying ambition and talent simply because they feel threatened.

On the flip side of the coin (i.e. the 5c) there is probably enough info on the net about labyrinth shroud seals to satisfy the original questioner so I guess its all about being out of solitary confinement when it comes to learning. That's ok with me.

If my Grandson had asked me the original question I would have done the cardboard stiffness thing but this is all easily verified by looking at a simple sine curve and analysing the first differential (if you land up near sixty degrees you're about there - isn't mother nature brilliant?)

Let it Bee.

Big Bad Bob

Big Bad Bob,

Nice that you call yourselve a guru, knowing a lot of the subject, but in fact you did not bring in anything that the originator could help.

I know nothing of seals and chemical process engineering. Previous responses learned me something interesting.

My world is structural, electric and thermal (Static and dynamic) So I tried to answer in simple words to the in fact good question, things that are not told in school.

Gwen

Hi, BBB

I read your response, and out of curiosity, rechecked Ranjan's entry blog #1, which I assume is the one that was being discussed, and which I'd read originally without alarm.

It still seems to make perfect sense to me --although he neglected to say what kind of material is being used on the 'plane turbines to form the honeycombed leeway spaces-- that both a honeycombed approach would be used for its geometric strength and also for the spaces between a honeycomb's comparatively thin walls that would allow it to be sliced by the (apparently) unshrouded blades as they form their own sealed path of travel.

I'd be curious to know

• which high-heat alloy is chosen for that task, and
• why 'plane turbines (and by inference gas turbine) blades are not shrouded, since in steam engineering shrouding is a really obvious way to reinforce the blades, and
• What happens to the turbine before the blades reach their heated rotational diametric zenith, in terms of sealing; or is the loss of power past the temporarily unsealed blades taken for granted until the turbine heats up?

But as far as doubting Ranjan's engineering understanding, I don't see anything in his blog that would make me do that.

Mark

PS I wasn't exactly sure which glands you meant in your blog...the shrouds are, in steam engineering at least, strips of reinforcing metal attached around the turbine blade tips; while the glands are multi-stepped spaces that prevent steam escape past the shafts at the ends of the turbine casings. Stator (fixed) blades and nozzle packing are used to prevent steam from passing unused between the rotor blades, which are often slightly recessed into the casings. Is that what you meant by glands? That arrangement could be considered a minimal form of glanding. -M

Hi Mark

•The vast majority of the honeycomb we make is of hastelloy-x, with inco625 second.

•They do use shrouds in jet turbines.

•The honeycomb rings and segments are softer than the blades, and are crushed/cut by the blade tips/knives on first fire-up. I presume, but do not know for fact, that they slightly overheat the engine on first fire-up to avoid rubbing at standard running temperature.

Dick

DK & Ranjan

Where are the shrouds on the gas turbines located if the tips are free to cut into the seal material?

And

One would presume that once cut by blades , according to Ranjan, are extended by the centrifugal force of the engine's thrust, that this leaves a space over the blade tip prior to the engine's warming up. Is anything done to replace the seal until warmup is complete, or is the initial thrust loss taken for granted?

BBB

The reason I used the term minimal is because the blade arrangements are not really labyrinthine, like the glands, so there is no condensation taking place through them.

Mark

Question : Why is honeycomb used ?

BBB : ...this is all easily verified by looking at a simple sine curve and analysing the first differential....

well , I suppose you at least jumped up and down on cardboard first. Nice progression BBB - goo goo gaga to high school math gobbledygook in one quick bound !

In lieu of a clearer question /answer I'll leave this one to a professional to really mix up . I jest , but I'd like to hear the teenage friendly version . At least you demonstrate the wide range of possible answers.

Honeycomb is what honey bees build:

to securely house themselves and their queen(mother),procreate in ,store the safest nutrition for the future generation.

Engineers copied this 3-dimensional wonder --comb-- and created all kinds of copies in 2 and 3 dimensions.

By copying the bees empirically,Engineers tried to get:

• Directionality(polarization) in Acoustics/Radiation/heat transfer
• Multiple sites of activity ( catalysis,chemical reactions)
• Strength in many directions with maximum use of tensile strength of metal/alloy.{ Yours Truly uses honeycombs of 300x250 cell size with 32x0.7mm cold-drawn C45 steel strips welded at corners--- to make light all-steel beds. Weight of single bed is 5Kg }
• Architects use Concrete honeycombs to strengthen and beautify`

There is no rigorous mathematical predictability/theory yet on optimisation of layers.