Tests results of 13 unique constructions

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George Gall and I laid-up 21 unique lamina schedules, then did three-point bending tests to acquire flex (stiffness), failure mode, failure strength, and toughness.  Then we did impact tests.  The results are attached in a spreadsheet.

Only 13 constructions are included because the others were tested at the beginning when we were still improving our test methods.  There are some good results in the missing tests, but they are not accurate...I am afraid I would get bombarded with questions and doubts if I posted them.
All the numbers listed in the spreadsheet pertain to a laminated block of eps foam that is 14”x4”x1.75”.  These are representative(proportional) of how a surfboard would perform/break BUT NOT THE SAME.  You have to keep in mind how things scale.
Here are definitions of the parameters you see in the spreadsheet:
Stiffness: The slope of the load/deflection curve in in the linear range.  A larger number indicates that a  surfboard with this construction is stiffer or less flexible.  (I did not include units...look at the numbers in comparison to the stock glass construction listed at the bottom E+E/E).
Toughness: The amount of energy that would be required to break the specimen in bending.  This is more important than the amount of weight required to break the specimen in bending.  Energy is calculated as the area under the load/deflection curve. 
Strength: The amount of weight required to break the specimen
foam density: density of the foam in the specimen
foam weight: weight of the foam in the specimen
board density: estimated weight of a 6'0” chip without fins
tough/weight ratio: structural performance index...toughest board for the weight
flex/weight ratio: structural performance index...most flexible board for the weight
impact rating: how well the specimens mitigated a severe impact. All impacts were identical

HOW TO USE THESE NUMBERS:
1)Choose the board that flexes the way you like.  Reference the layups that you know ( W+W / W or E+E / E).  Do you want your board stiffer or more flexible than one of these layups?  Look at the stiffness numbers, then find a few that meet your flex criteria.
2) Amongst the boards that flex properly, find the happiest medium of weight, toughness and impact resistance.

Of course the constructions that I tested were engineered to be flexible, lightweight and tough.  Some of you may be looking for heavy, stiff boards, so you'll have to run your own tests.

**Please note that the W+W / W and E+E / E were laid up with denser foam, so they will appear to be tougher and stronger than they should be.  A higher density EPS foam greatly increases the toughness and strength, but does not effect stiffness.  Foam has a negligible effect on the surfboard stiffness.

https://swaylocks7stage.s3.us-east-2.amazonaws.com/s3fs-public/iteration2b_xls_4becac7903.xls

Ben;

Tried to upload your file, what's the program?

Any stuff that has Engineer George involved, I

want to pay attention! LOL  looking forward to

the resulting chaos......

It's an Excel spreadsheet - should be able to read it with the MSWorks Spreadsheet software, most any spreadsheet software, MSWord, etc. Or download http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=1cd6acf9-ce06-4e1c-8dcf-f33f669dbc3a for a viewer.

Or, go whole hog and give http://www.openoffice.org/ a shot, which runs on damned near anything.

hope that's of use

doc...

Nice work, Ben.  GWN said it best.

Yeah, I’ll donate.

Blessings to ya.

Hi Benjamin -

Are you planning to continue testing with rectangular panels or are you going to be glassing actual shaped blanks? 

That’s great Benjamin !!! I haven’t seen all the keys… what’s 1.4(+60), 1.4(-60), 1.4(45) ? I love that stuff.

 

Does putting fibers at 45° change the impact rating (I would guess not) ?

 

google docs can accomodate the .XLS files as well…

this could be interesting.

KEY:

Stiffness: The slope of the load/deflection curve in in the linear
range. A larger number indicates that a surfboard with this
construction is stiffer or less flexible. (I did not include
units…look at the numbers in comparison to the stock glass
construction listed at the bottom E+E/E).

Toughness: The amount of energy that would be required to break the
specimen in bending. This is more important than the amount of weight
required to break the specimen in bending. Energy is calculated as the
area under the load/deflection curve.

Strength: The amount of weight
required to break the specimen

Foam density: density of the foam in the specimen

Foam weight: weight of the foam in the specimen

Board density: estimated weight of a 6’0” chip without fins

Tough/weight ratio: structural performance index…toughest board for
the weight

Flex/weight ratio: structural performance index…most flexible board
for the weight

Impact rating: how well the specimens mitigated a severe impact. All
impacts were identical

 

1.4 :  a 1.4 oz E-glass cloth…datasheet attached

3 : a 3 oz 4harness Satin cloth…datasheet attached

 

EXAMPLE:

3 1.4(+60), 1.4(-60) / "

From top to bottom
3 oz 4h Satin oriented at 0,90 (0deg fibers are aligned with stringer pointing to the nose)
1.4 oz oriented at 60,-30   (the 0deg fibers are rotated 60deg to the RIGHT, so the 90deg fibers end up at -30deg)
1.4 oz oriented at -60,30   (the 0deg fibers are rotated 60deg to the LEFT)
1.75" EPS Foam
1.4 oz oriented at -60,30  
1.4 oz oriented at 60,-30 
3 oz 4h Satin oriented at 0,90

1.4 oz E-glass

3 oz 4harness Satin cloth

 

This stuff should be the new industry standard.  I’m getting all my boards with this now.

IF you are only comparing one layer of cloth in a laminate:  0,90 vs. 45,-45…No

 

However, let’s assume you have more than one layer and all layers are standard 4oz cloth, and some layers are rotated.

If you have two layers, total weight 8oz

(0,90 / 0,90)
(0,90 / 45,-45)

The latter will be significantly more resistant to impacts.  It will also be more flexible.  The first one only has two axis of fibers.  The latter has 4 axis of fibers.  The more axis of fibers you have, the better it will be for impact.

For three layers, total weight 12oz

(0,90 / -45,+45 / 0,90) will be good for preventing buckling and third best for impacts  (4 axis of fibers)
(0,90 /  0,90 / -45,+45 ) will be tied second best to mitigate impacts  (4 axis of fibers)
(0,90 /  -45,+45 / -45,+45 ) will be tied second best to mitigate impacts, but more flex than previous (4 axis of fibers)
(0,90 /  -30,60 / 30,-60 ) will be best to mitigate impacts   (6 axis of fibers!)
(0,90 /  0,90 / 0,90 ) will be the stiffest and the worst for impacts, same buckling resistance as the first (2 axis of fibers)

All of these schedules can
be fabricated quite easily for shortboards under 6’6" with a 60" roll
of 0,90 4oz e-glass…the exact same cloth that you use on shortboards,
but on a wide roll.  Graphite Master sells it and it’s cheap.  Roll the
60" out on a table, lay your board at the desired angle, then cut.

Personally, I think all non-sandwiched layups should be done with
three layers and MOST importantly have a -45,+45 layer of cloth IN
CONJUNCTION with a 0,90 cloth. (The 30/60 deg orientations probably aren’t worth the effort…even though they are the best)  In other words you should NEVER have a
layup that has 2 axis of fibers.  That means X-glass should not be used
by itself.  Even though 99% of
surfboards are made with only 2-axis of fibers, this is bad practice.

This is VERY COOL, it will take some studying. There was a lot of work put into this. At first glance, it seems to confirm my penchant for “S” glass. Thanks for sharing this test B.T. How much weight is added by 6 axis lay-up?

Nice work $5 is less than the price of a pint of beer here!

All of the variations on 3 layers of 4oz cloth (12oz total) that I listed two posts ago, will weigh the same.  Changing the orientation of the cloth does not changed the weight of the cloth or the resin absorption.

This is a big deal; many conclusions people will have already come to on their own, or through the composites literature, but experimental evidence always ends all doubt. Nice resource and thanks for sharing!

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This is a big deal; many conclusions people will have already come to on their own, or through the composites literature, but experimental evidence always ends all doubt. Nice resource and thanks for sharing!

[/quote]

Dammit- I was gonna say something, but you put it better than I could have. This also yields results important for those of us...yeah, the alternative forms types...who want to build flex into our surf machines.

If there's no numbers, it's just handwaving, y'know? Well done!

doc...

Thanks for the enthusiasm guys.

I just got some bad news about 30 mins ago, that the foam supplier we wanted to go with won’t be able to donate blanks.  Nobody’s rich in this industry.  We need 8 blanks to continue with this study.  All other materials have been donated:

FCS donated fins and plugs.
Graphite Master donated all cloths and resin.
Plus One Surfboards is donating their facilities…George Gall is donating A LOT of his time.
We’ve had quite a few donations from swaylock members that are going to cover some of the sensors.  Last donor was pompano about a month ago…very generous…Thanks!

Anyway…

**We need $350 to buy the blanks.  **If you guys like what we’re doing, please donate $5, $50, or $350, whatever you can afford.  A lot of little costs have been coming out of my pocket…they add up quickly for a grad student.

Swaylock founder, Michael Paler, posted a paypal account for anybody to donate to this project.  On the first post of this thread.

http://www2.swaylocks.com/forums/swaylocks-fundraiser-to-measure-effects-flex-surfboard

Thanks!

Ben,

Is this the same as or similar to what GraphiteMaster sells called Impact Glass?

regards,

Dave D

lol.  We’ve been using CF on different axial ratios for years.  We have to do it to dial in expansion and contraction and stiffness.  Of course we’re more worried about CTE’s when our products are in space going through extreme solar loads during orbit.  I always wondered when someone would get around to doing this stuff with surfboards.  I even used to mention it to Loehr.  Ben, I’m glad to see my donation is going to hands on stuff.  Keep up the good work.

Very good job benjamin.

After your first post about flex (as i’m mecanical teacher i like theory) i start to make lot of panel test, simple than your’s because i can’t do dynamic tests. I found that multiaxial structures were better and i found that less crimp in fiber were better too. I found that veneer can have a good stiffeness/weight ratio and a good resilience/stiffeness ratio.

Then, one day, i found that all those tests were ever made. That’s why for high quality composits, people use multiple UD fibers coats well oriented and autocalve to achieve an high fiber/resin ratio.

But it’s not cool for swirls.

Sorry for my frenglish.