Engineering values group

Hello all

I am intrigued with getting some data from the building sheds around the world on the real engineering abilities of the materials we use. Would anyone out there be interested in making some test samples from waste materials and then testing them in a way we could agree on?

The engineering data would be very useful for designers so that they could design structures that we could actually build rather than waht guys in nice white lab coats could do.

I was thinking of making a simple test beam say 1000mm long 100 wide that undergoes a deflection test to work out its properties. Has this been done before?

cheers

Phil Thompson

 

Good one

i would like to know
how to test WBP plywood

boil a piece
how big how long what should it look like afterwards

put weight on a long narrow piece until it breaks

what does good lamination practice look like

 

What's the scope of the data?

What conclusion should we be trying to arrive to, fractures of sample, tension, rigidity, laterateral forces, impacts, adhieveness, I can make mock-up of wood beams, nidacore, extruded fiberglass, carbon composite boards, and plain pvc, and I too would like to have access to a table that plots which one is the strongest, the lightest, and the can absorb the most abuse, but to get there I think we have to narrow the scope of what were after....if your even after the same conclusions I am?

 

Simple data first

Hello Baywolf

I am interested in some extremely simple test values. How about a thickness of normal laminates.

test data is expressed in Pascals or whatever - a pressure.

One of my references has a typical E glass uni laminate with an E of 35-50 GPa. I don't know if this is reasonable to assume blokes in sheds can produce this.

One - they may not be able to stack the laminates together as well as the test lab so the number of fibres per unit area is lower.

Two - after handling and normal rough use the fibres may degrade and take less load before failure.

Three - people in sheds may have operating issues that mean they can't obtain technical perfection

So I would like to know how thick a laminate of for example 4 plies of 600gm uni is in different sheds. That would give me something to use when engineering a beam.

Then make up a series of test pieces and get a simple E value for different composites. I was thinking of a foam sandwich simply supported beam 1 metre between supports, 100mm wide and 10mm thick with one layer of 600gm uni both sides to start with. A 10 kg load and measure deflection and then load up to failure.

What do you think about this?

Cheers

Phil Thompson

 

Phil, I can measure some thicknesses acheived in uni compaction on some of my bulkhead opening caps- their in iso poly with chop but may be of help- they mostly comprise 880gsm uni material, I also have some spare 600 x 600 test panels & impact(cannonball) test results available along with a busted carbon/cedar mast in my yard. Also catmando who has posted here & also to cruisers & sailing forum has represented some simple & similar test data for kiri vs cedar strip plank I think Regards from Jeff.

 

Phil, in regards to a laminate stack thickness, yesterday at work I measured this uni reinforced cap on a bulkhead molding in way of the door jamb reveal appeture
gelcoat- about .6mm
225gsm chop
450gsm DB
225 chop
6 x 880gsm uni
300gsm chop
450gsm DB
300gsm chop
Thickness measured was around 9-10mm & .6 mm less discounting the gelcoat thickness so say 9mm for the stack above, some areas up to 11/12 mm but accounted for in the overlapping sequence of the uni installation for a total mixed glass content(chop/uni & DB) of around 7200gsm averaging 800gsm per mm of thickness, fiber compaction by hand/brush/roller only. Regards from Jeff

 

Thanks Jeff

That is the sortof stuff I am thinking of. I guess I should get some foam and start making some test beams myself. Once the stacking is done I can work out the Young's modulus.

I guess I could get some verniers and rip of different laminates. Have you got some sensitive verniers for laminates less than 1mm and some samples? Do you think this would be a good way to do it?

cheers

Phil

 

Phil, yes I've got verniers but used a steel rule on the cut laminate edge in the above example, some furthur parameters for your beam test might apply too like say 1200mm long but supported at 1000mm centres on 25mm roundbar & the load(maybe water in a bucket/pail) interfacing the beam at the halfway point 500-500mm from the beam supports again using 25mm roundbar & a yoke to the underslung bucket or whatever, deflection can be measured with a strait edge on blocks over the end supports with the "tail" of the verniers & the straitedge needs to be turned over to average out any "unstraitness" in it, without some standard the test is a lot tougher to compare samples. In the "cannonball" test 600mm square samples are supported on a 500mm square opening with an angle iron frame, the weight(I cant remember off hand the kgs & end radius) is dropped in 500mm sequentially increaseing collisions on the same outlined spot & expression & depression measured on the laminate faces after every drop, cumulative crack length is also recorded along with whitening(delamination) area until laminate failure-/perforation. All the best from Jeff

 

Deflection test

I like the standards for the deflection test. Are you interested in doing some too? I can get into the shed and make some samples. Then I can reverse engineer them to get the Youngs modulus.

It looks like it just be you and me. However if word gets out I think the values will find their way into somewhat common usage.

I will have a look in the shed and see what I can find to make the first test piece. I used to have some 12mm foam around.

cheers

Phil

 

Phil,
Yeah, I'm keen to do a few samples, I've got some core laying around, but have to get the time to spend on it, most of the fabric here is quad which probably dosn't represent so well in the beam test, the uni is gunna be the best in the narrow samples. I'll be interested to see the calcs worked on this but don't have the math/s for it. All the best from Jeff

 

For laminate and sandwich beam properties there are guidelines you can follow in order to ensure proper failure.

As an example, I wanted to compare scored vs. plain sandwich core laminate flextural strength which called for ASTM (American Standards of Tests and Measurements) C393-06 which specified beam length, width, support span length, load span length, load application rate, etc.

Here is a picture of one of the tests:



What I suggest is to either go to a local university and request such tests or pay one of the many companies that will perform tests for you. Going through a university will cost more as they are required to charge more than a professional company.

 

Thanks eathena

Ta for the heads up about uni testing. I am aware of unis doing testing but I am more interested in doing a sort of wiki materials database.

There are lots of designers using numbers for materials derived from lab tests. It would be really worthwhile if lots of builders worldwide could generate some data from their own sheds. Then designers would have factual amateur building data to use - I think a thickness/gm and a Youngs modulus would be a very good first step. Therefore I think that Jeff's idea is the easiest. I will source some extra foam and see if I can't start this off myself.

cheers

Phil Thompson

 

Catsketcher

I too think it would be nice to see how the average workshop produced laminate compares to the lab one. But I dont know how usefull data from non standard tests would be.
What would be more valuble is for members that have had laminates tested by standard methods is to share this information. I will see if any of my cotacts have any such data to get things going.

I have made a few measurements of the laminates that I made and found that for the typical 30% volume fraction stitched E glass the thickness in mm is 1.2 times the weight in kg/m2 when hand laminated with peel ply.
Same fabrics when consolidated with >80% vacuum multiply kg/m2 by 0.9.

Also have made a couple of test laminates of UD glass for my chainplate and mast connection beam flange schedules for my 12m cat I am building.

Flange laminate is 12,600g (24x450g UD + 4x450gDB)
this I infused and it is 11.0mm thick at 29% resin by weight. Unfortunately I dont have a hand laminate for comparison but I would expect it to be around 15mm.

Chain plate laminate using 1,000g UD tape which I think is a Colan product, this is a lot higher fiber volume fraction material as even hand laminate came in at 30% wt resin.

Laminate is 12,900g (12x 1,000g UD + 2x 450g DB)
Hand laminate is 8.6mm at 30.2% resin.
Infused laminate is 7.7mm at 22.4% resin.

Cheers
Andrew

 

Catsketcher

Unfortunately non of my contacts had any laminates tested.
Modulus data for E glass that I have seen quoted is in the range of 5 - 40MPa. 5 being for a chopped strand laminate and 40 for an autoclaved UD laminate. For a very good UD E glass 30% vol fraction cloth infused laminate 30 - 35 MPa, and 25MPa for a hand lay up.

Have a look at http://www.vectorply.com/ they provide properties for their range of reinforcements, both for hand lay up and infused in many cases.

Also you can download free laminate design software,this is meant to be close to real world as they claim to use real world resin properties in the calculations.

Regards
Andrew