Date

10 Oct 2022

Attendees

Item

Procedure

Media

Analysis

General

Load vs Displacement for All Samples

Load vs Displacement for All Samples Until Failure

Alignment of CF Dog Bone in Fixture

Alignment of Lap Shear Sample in Fixture

Comparison of Surface Finishes of IREC 2022 (bottom) and 9/17 (top) winds

All samples follow a similar modulus of elasticity. This suggests that the behavior of each bond is similar
Sample 1 experienced significant slippage and therefore experienced significant displacement
It was difficult to effectively use the shims
- Some shims were slightly too big
- Even at best the samples were not perfectly vertical
- The shims sometimes slipped in the fixture
All tests were performed using a strain rate, however in an actual application each load would be instantaneous
The surface finishes of each CF sample were significantly different
- The IREC 2022 wind had a more uniform and smoother surface finish on the inside face
- The 9/17 wind had divots and blemishes, resulting in stress concentrations in certain parts of the sample
Stress could not be calculated due to complex part geometry

Conclusion:

Lap Shear

Load vs Displacement for Lap Shear tests (omitting Sample 1)

Load vs Displacement for Lap Shear Tests Until Failure

Sample 1 broke in fixture. Need to reapply epoxy
Sample 2 broke at bond
Sample 3 broke at CF part, failed due to poor surface finish
Sample 4 broke at CF part, failed due to poor surface finish
Sample 5 failed at CF part, however no significant deformation. CF part buckled
Sample 6 failed at bond, epoxy bonded better with exterior surface finish
Sample 7 failed at bond, epoxy bonded better to interior surface finish
Samples 2 through 5 were the strongest of the lap shear samples
- Samples 3, 4, and 5 failed at the CF
- Sample 2 failed at the bond
Samples 6 and 7 were the weakest
- They failed the same way
- the bonds were not as strong?

Dog Bone

Load vs Displacement for Coupon Tests

Load vs Displacement for Coupon Tests Until Failure

All parts failed near jaws
- Jaws are flat, part is slightly curved. This caused stress concentrations
Epoxy matrix failed first, then the CF fibers
- Buckling =/= total failure?
- After failure (the maximum load) each sample deformed prior to complete failure
Samples 8 and 9 were the strongest
- This could be attributed to a better surface finish
- Better surface finish = stronger part?