Overview
The objective of these experiments was to determine a more accurate estimate of the ply properties of our carbon fiber with the Systems 3000 laminating epoxy. We created test coupons comprised of N (0/90) plies, and three strain gauges (x, y, xy) were attached to each coupon. Tensile tests were conducted using the IN-STRON machine in 1-307. From the stress-strain data, we were able to acquire E11, E22, G, and Poisson's ratio.
Laminate 1
We had a mishap when making the first coupons, when the carbon fiber layers had tape with labels put dead center on each sheet, rendering the centers unusable. We tried to salvage the fibers, but the coupons came out too small. It was still very useful in learning that the size of coupons would need to be heavily revised for the next round of testing, and that the surface finish was far from optimal. We used the mistakes from the first round to ensure that the second round would be perfect for testing.
Laminate 2
These samples were longer and thinner (10in x 1in) and as shown above (ft. Dylan Hall), are successfully hooked up to the instron. We use 3 strain gauges, and can use the combined data to determine the poisson's ratio, Young's modulus and shear modulus.
Shown above are a close up of a sample coupon, the full sheet prior to water jetting, and the sample being released from its metal sandwiching, in that order. The surface quality on one side is still far from perfect, but with sanding, is more than acceptable. The full sheet is a major upgrade, as we were able to generate a healthy 8 samples with the desired dimensions to be tested on the machine. We used metal plates to compress and improve the surface finish for the instron to grip our samples.
We observed a small amount of internal stress (manifesting as bending) within our main sample, but have ruled out thermal and ply orientation as reasons for this occurring.
Measurement (&Calculations)
Google sheet where I kept measurements
Young's Moduli
specimen a 1kN.xlsx (E = 92.743 GPa w/ R^2 = 0.9969)
specimen b 5kN.xlsx (E = 71.694 GPa w/ R^2 = 0.9999)
specimen c 5kN.xlsx (E = 121.13 GPa w/ R^2 = 0.9993)
specimen c 1kN.xlsx (E = 121.91 GPa w/ R^2 = 0.9979)
As of 11/20/2019 we have only been able to test 3 samples with the methods detailed above. Specimen a was tested first, followed by specimen c. We determined that not only would the specimen's be safely (without fear of failure) up to 5kN, we found that the data agreed with itself between 1kN to 5kN pretty well and based on this we are confident in our results between specimens regardless of final force. That being said, going forward we will be using 5kN because there is no such thing as too much data.
Each specimen file (.xlsx) has separate windows for axial, shear and transverse stresses.
Poisson's Ratio
I need to confer with Dylan and update this soon. One of the .xlsx files has a very sparse version of the calculations we did, but I'll get a more in depth notation by this weekend.