# Coffee Cup - Honeycomb Sandwich Structure

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## Introduction: Coffee Cup - Honeycomb Sandwich Structure

So you think your coffee is strong? Wait until you have tried your coffee cup!

"A Honeycomb core is an array of hollow columns made of sheet material which is used to separate the two facings of a sandwich structure".

So why not make one of Coffee Cups and enter the Coffee Cup Challenge?

This I'ble will show you how to make a honeycomb panel as a building block for your future projects.  If you like it, don't forget to vote for me!

Note
Where I live, paper cups are somewhat rare, so I have merely made a beam and tested it.
My project has ended by testing this beam. If you want to take it to the next level or if you have an awesome idea, feel free to use this information and even post it in the Coffee Cup Challenge as well (some credits would be nice though).

## Step 1: What Do You Need?

It's a great misconception that you need fancy materials to fabricate composite materials. Nature is full of extraordinary examples.

You will need:
* 45 coffee cups
* two triplex strips of 90 x 20 cm (thickness 2 mm).
* Glue.

The dimension of the strip was more or less determined by the fact that I could only get hold of 45 cups (3 rows of 15 cups).

## Step 2: How It's Made.

1. Apply glue to one side of the first strip (preferably with a brush)
2. Place the cups in an alternating pattern.
3. Apply glue to the second strip and place it on top of the cup.

## Step 3: Testing.

As expected, the beam is very light (900 g).
The test dummy on the picture (me) weighs 80 kg.

Picture 1 & 2
As expected, with pure compression, nothing much happens. Not a crack.

Picture 3
Now it became critical. Upon mounting I could hear some cracks (didn't stay too long on top).

Picture 4
I mounted again with two feet and told the photographer that I would lift my left foot on the count of three. He had to push the button at the same time. The structure collapsed almost immediately.
I was very lucky because: the picture is perfect and I didn't strain my ankle.

## Step 4: Room for Improvement & Applications

I believe you can really make a strong structure with these materials, however there is room for improvement:

1. Arrange the array of cups more neatly (symmetrical).

2. When I applied the glue, I noticed that a lot of it was absorbed by the triplex. Therefore the bond with the cups was likely to be less strong. I neglected this fact.

3. I Added approximately 70 kg of weight where I should have used a vacuum bagging technique. This could have easily increased the "weight" tenfold (700 kg spread evenly). This was a deliberate choice as I wanted to keep the project simple.

4. Some of the coffee cups didn't have a flat surface anymore. Apparently, people often bite in these cups. This reduced the bond as well.

5. In the previous step you can see that one block (on which the beam rested) was slightly higher than the other one, resulting in high local tension probably.

So should we phone NASA and tell them that we have the new building block for their next spacecraft?
It all depends on the confidence that you have in your production process.

Definitely: tables, doors, panels, hatches, shelfs
Probably: light construction elements.
Unlikely: aerospace!

Finalist in the
Coffee Cup Challenge

## Recommendations

• ### 3D CAM and CNC Class

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## 58 Discussions

this is great, good thinking! I think these would not be as thermally resistant or as strong as SIP's but a lot more cost effective for a lot of purposes. I am thinking about farm structures, chicken houses, rabbit hutches, small barns. Not taking away from the Styrofoam cup concept but free association brings me to the next obvious choice being aluminum drink cans. You could set a house on one of those!
I am looking forward to your next project, whatever it may be.

Thanks!
In the discussions on the main page, you can find a discussion about using aluminium cans (Coke).

Pay very much attention to the glue bond between the cups and the skin. This is the most important aspect of the strength!

Show us the results when you're done!

You heard about that group that made a bridge span 5 metres, that held 200kg and was made of paddle pop sticks and glue?

6 replies

there are annual competitions all over the country, and the world, for this. google popsicle bridge competition and you'll find all you want. the great ones are where, rather than unlimited sticks, the contest is to make the strongest bridge with a small number.

this is a TORSION BOX, way way cool. i'm thinking of two sheets of glass bound by epoxied glasses!

Just do it! Would be cool, don't forget to post it.
(alternatively, use Gorilla Glue, enter the Gorilla Glue competition and win some of the prizes...)

If you filled the voids (outside the cups, not inside) with expanding foam, or some other adhesive, light, form-filling material, you would eliminate the "weak points", which is the only thing wrong with this very BRILLIANT idea of yours.  Not only that, but it would then be an insulating material.

2 replies

expanding foam expands and will dent the cup walls. this is like the old "stand on a pepsi can" trick.

That's just one step away from getting rid of the cups all along and to go for a foam core!
However, I think your suggestion could work and your point is that there is room for improvement (as stated by myself in step 4 of this I'ble).
Only thing is, currently I don't have the time nor the resources to take it that step further (hope that someone else will. you?). That's why I made the remarks in step 1 about the contest. I'll be happy to contribute.

Oh yeah, air is one of the best insulators around!

What is a "triplex strip"?

Could one just use corrugated cardboard?
If so, coroplast would also work (corrugated extrusions of plastic) but it is more expensive.  \$10 for an 8' x 4' sheet here, from a sign shop.

2 replies

dumpster dive cardboard boxes. cut into 4" strips (cut across corrugation) and roll (pop-can) into tubes, glue between face cardboard strips (the corrugation lines should run parallel to the longest dimension.
you can make the faces stronger by doubling the face, or by cutting the faces on the bias with the corrugation at right angles to each other.

Triplex is just plywood (so I have learned in the discussion at the intro of this I'ble).
I guess you could use cardboard, just as long it doesn't get wet (but then the same applies for the cups!). The skin of the sandwich panel must withstand tension and compression. So the cardboard may not be too thin.
Coroplast might work as well, but seems a bit expensive? (but will paper adhere to plastic?) If money is no problem, I would get rid of the coffee cups all together, but then that's not so much fun!