I started conducting material tests. The objectives for the tests are:
1. Compare the strength of different layups materials.
2. Determine if Polyurethane Glue (Gorilla Glue) is a suitable bonding agent.
3. Compare strength differences between epoxy and Polyurethane Glue.
Hopefully you’ll find this information useful.
I started the tests with poly-u glue first since I wanted to see how well it bonds. The reason I chose a cork layup is because someday I’d like to start using it in a ski, perhaps a “green” ski to provide a damping effect.
All materials below measure 3in wide x 36in long (76.2mm x 914.4mm). Each sample contains 2 layers of maple veneer for the core. All samples were pressed separately without heat.
I plan on conducting more tests with other materials as time goes on.
Material list to date:
FG - Triax 20 oz with 7 carbon fiber strips
Core - maple 1/16in thick (1.6mm)
Cork - .8mm
AL - .24mm thick (sanded using 80 grit to increase adhesion)
Epoxy - QCM EMV 0049 resin ECA 032 hardener
Polyurethane Glue - Gorilla glue (approx 14 fluid oz used in the 3 tests).
Water - I dampened all the materials before layup as suggested by the makers of
Gorilla glue.
VDS
Ptex base
30lb weight (13.6 kilo)
Wixey Digital Angle gauge model WR300 to measure angle of deflection
Torque Wrench - Applied 10 foot lbs of torque
Pic of fiberglass with epoxy, PolyU-Glue, wood glue, some tools:
Layup Samples:
PolyU-Glue Observations:
As expected the metal layup was extremely firm. I used VDS with the AL to provide better adhesion. It retained 5mm camber where the others had little or no camber. The FG layup was the next firmest with the cork being the softest. No surprise here.
PolyU-Glue Bonding Results:
No problems with the bonding of materials using Polyurethane glue. As expected the Fiber Glass layup required the most amount of glue in order to work it into the fibers.
The glue expands 4-5 times when curing. I wondered how this would affect the bonding of the materials. But it seems fine.
Torsion testing:
I conducted 2 types of Torsion tests. In the first test I set up a simple torsion apparatus similar to the ones used in the links below:
http://www.skibuilders.com/phpBB2/viewt ... c&start=90
http://www.doctorsnowboard.co.uk/?page_id=305
I noticed during my testing the position of the torsion apparatus in relation to the samples is important as the measurements could vary during the tests if the setup was not consistent from one test to the next. I conducted torsion tests at a single 6in interval on each sample using a 30lb weight to twist each sample. I zeroed out the Angle meter before conducting each test and then applied the weight.
I noticed as was I testing the sample layups were also bending upward slightly. While I did not want that to occur, I couldn’t prevent it so I had to be as consistent as possible with the setup and positioning of the apparatus. I only used the first Torsion test on the PolyU-Glue samples.
The second Torsion test was performed using a Torque Wrench and the Wixey Digital meter. I clamped the test sample to a work table so that 6 inches of the sample over hanged the table. I applied 10lbs of force and measure the angle. Since the Torque Wrench is not super accurate I ran 3 tests on each sample and took an avg reading.
Torque Wrench Torsion setup:
Torsion Results:
First Torsion Test on PolyU-Glue samples was performed using a 30lb weight.
Second Torsion test on PolyU-Glue samples with Torque Wrench 10 foot/lbs:
Third Torsion test on Epoxy samples with Torque Wrench 10 foot/lbs:
This chart is a comparison of all 3 Torsion tests:
Looking at the numbers above, the metal sample is twice as firm as the FG sample and nearly 4 times more firm than the Cork sample at the 6 inch mark.
Deflection testing:
Each sample layup was clamped 6inches from each end to work tables. A 30lb weight was suspended from the center of the samples. I measured the amount of deflection in millimeters at the center point.
Deflection Results:
First Deflection test on PolyU-Glue samples:
Second Deflection test on Epoxy samples:
This chart is a comparison of the Deflections tests:
Summary
I’m a little bit surprised at the difference between the metal layup and the fiber glass layup. The metal layup is about 2-3 times stronger than the fiber glass layup. No surprise about the cork.
The results of the epoxy tests compared to the poly-u glue test surprised my a little bit. Overall I think Poly-U glue works “just about as well” as epoxy. Poly-U Glue bonded to all the materials in the tests just as well as epoxy. I expected a larger difference between the epoxy samples aband the corresponding PolyU-Glue samples. The only big difference between the samples is the epoxy samples retained much more camber than the Poly-U glue samples.
The cork performed poorly in both samples. Not sure if cork will provide the damping effects I thought it could. It definitely does not provide any serious re-enforcement of any kind. It was super wet noodle boingy boingy ( ie no pop, just flop).
Please feel free to re-comment if you like.