1. Elastic Properties of K13D2U/Epoxy Prepreg
Mark E. Tuttle, University of Washington

2. Elastic Properties of K13D2U/Epoxy Prepreg Preliminary Comments
Current design of L0 support structure involves a six-ply [0/20/-20]s laminate (used in outer castellated shell) and a three-ply [0/90/0] laminate (used in inner cylindrical tube)
The elastic properties of the [0/20/-20]s and [0/90/0] laminates will differ substantially
By measuring the in-plane properties listed below for an individual ply, in-plane elastic properties of any multi-angle laminate can be predicted using lamination theory:
E1 and E2 (moduli parallel and perpendicular to fiber direction)
n12 (“major” Poisson ratio)
G12 (shear modulus)

3. Elastic Properties of K13D2U/Epoxy Prepreg Objectives
To measure unidirectional properties (E1, E2, n12, and G12) exhibited by the K13D2U/epoxy composite delivered by Fermilab to the UW
Use lamination theory to predict Ex and nxy exhibited by a [0/20/-20]s laminate
To compare predictions to measurements obtained using a [0/20/-20]s tensile specimen machined from a prototype castellated outer shell
(…subsequently, updated FEA analyses of the L0 support structure was performed by C.H. Daly, based on measured elastic properties)

4. Technical Approach Measurement of unidirectional properties
E1 and n12: Measured using biaxial strain gages rosettes, mounted back-to-back on a [0]6 tensile specimen
E2: Measured using uniaxial strain gages, mounted back-to-back on a [90]6 tensile specimen

5. Technical Approach Measurement of unidirectional properties
G12: Measured using biaxial strain gages rosettes, mounted back-to-back on a [45/-45]s tensile specimen (This technique described in Whitney, Daniel, Pipes, Experimental Mechanics of Fiber Reinforced Composite Materials, Chapter 4, ISBN )

6. Technical Approach Measurement of Ex and nxy for [0/20/-20]s laminate
Ex and nxy: Measured using biaxial strain gages rosettes, mounted back-to-back on a [0/20/-20]s tensile specimen machined from prototype outer castellated shell

7. Preparation of [0]6, [90]6, and [45/-45]s Specimens
Three flat rectangular panels with required stacking sequences were prepared using a Tetrahedron MTP Programmable Hot Press
One surface of the panels was adjacent to an aluminum plate coated with release agent (the “tool” side), while the opposite surface was adjacent to a porous teflon release ply (the “fabric” side)
Cure cycle imposed using the hot press (pressure, temperature, time) simulated the autoclave cure cycle used to produce prototype outer and inner shells
Tensile specimens were machined from these panels using a diamond-coated abrasive cut-off wheel

8. Specimen Preparation - Unidirectional Tests
(Nominal) physical dimensions:
[0]6 specimens: x x 7 in
[90]6 specimens: x x 6 in
[45/-45]s specimens: x x 6 in
Comments:
Nominal ply thickness was in for [0]6 and [90]6 specimens and for [45/-45]s specimens
To conserve material, specimens were much thinner than is “customary”, and aspect ratios did not meet ASTM specification of 10-12

9. Test Equipment Instron Model TM-M-L table-top test frame
Vishay Series 2100 strain gage amplifiers
Mac IIci equipped with National Instruments A/D board and LabView Software package

10. [0]6 Specimen

11. [0]6 Specimen

12. [0]6 Specimen

13. [0]6 Specimen

14. [90]6 Specimen

15. [90]6 Specimen

16. [45/-45]s Specimen

17. [45/-45]s Specimen

18. [45/-45]s Specimen

19. [45/-45]s Specimen Calculation of G12
The shear modulus implied by these measurements is*: (Whitney, Daniels, Pipes, Experimental Mechanics of Fiber Reinforced Materials, Chapter 4, ISBN )

20. Summary of Measured Unidirectional Properties and Predictions for a [0/20/-20]s Laminate
E1 = 59.5 Msi n12 = 0.39
E2 = Msi G12 = Msi
Predicted properties for a [0/20/-20]s laminate:
Ex = 38.4 Msi nxy = 3.0
Ey = 1.08 Msi Gxy = 4.55 Msi

21. [0/20/-20]s Specimen

22. [0/20/-20]s Specimen (Predicted Ex = 38.4 Msi)

23. [0/20/-20]s Specimen (Predicted nxy = 3.0)

24. Sensitivity Study Variation in Exx for [0/+q/-q]s Laminates

25. Sensitivity Study Variation in nxy for [0/+q/-q]s Laminates

26. Sensitivity Study Variation in Eyy and Gxy for [0/+q/-q]s Laminates

27. Discussion
Only one measurement has been made for all specimen types; results obtained are not valid in a statistical sense
Specimen thickness is smaller than is customary, and in-plane aspect ratios are lower than ASTM specifications
Nevertheless, comparisons between measurement and prediction for a [0/20/-20]s laminate are reasonable
Given material costs, measured properties are sufficient for present purposes