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

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Presentation on theme: "1 Elastic Properties of K13D2U/Epoxy Prepreg Mark E. Tuttle, University of Washington"— Presentation transcript:

1 1 Elastic Properties of K13D2U/Epoxy Prepreg Mark E. Tuttle, University of Washington tuttle@u.washington.edu

2 2 Elastic Properties of K13D2U/Epoxy Prepreg Preliminary Comments l 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) l The elastic properties of the [0/20/-20] s and [0/90/0] laminates will differ substantially l 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: E 1 and E 2 (moduli parallel and perpendicular to fiber direction) 12 (“major” Poisson ratio) G 12 (shear modulus)

3 3 Elastic Properties of K13D2U/Epoxy Prepreg Objectives To measure unidirectional properties (E 1, E 2, 12, and G 12 ) exhibited by the K13D2U/epoxy composite delivered by Fermilab to the UW Use lamination theory to predict E x and xy exhibited by a [0/20/-20] s laminate l 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 4 Technical Approach Measurement of unidirectional properties E 1 and 12 : Measured using biaxial strain gages rosettes, mounted back- to-back on a [0] 6 tensile specimen l E 2 : Measured using uniaxial strain gages, mounted back-to-back on a [90] 6 tensile specimen

5 5 Technical Approach Measurement of unidirectional properties l G 12 : 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 0-912053-01-1)

6 6 Technical Approach Measurement of E x and xy for [0/20/-20]s laminate E x and xy : 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 7 Preparation of [0] 6, [90] 6, and [45/-45] s Specimens l Three flat rectangular panels with required stacking sequences were prepared using a Tetrahedron MTP Programmable Hot Press l 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) l Cure cycle imposed using the hot press (pressure, temperature, time) simulated the autoclave cure cycle used to produce prototype outer and inner shells l Tensile specimens were machined from these panels using a diamond-coated abrasive cut-off wheel

8 8 Specimen Preparation - Unidirectional Tests l (Nominal) physical dimensions: è [0] 6 specimens: 0.0140 x 0.7450 x 7 in è [90] 6 specimens: 0.0140 x 0.7450 x 6 in è [45/-45] s specimens: 0.0120 x 0.7450 x 6 in l Comments: è Nominal ply thickness was 0.0024 in for [0] 6 and [90] 6 specimens and 0.0030 for [45/-45] s specimens è To conserve material, specimens were much thinner than is “customary”, and aspect ratios did not meet ASTM specification of 10-12

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

10 10 [0] 6 Specimen

11 11 [0] 6 Specimen

12 12 [0] 6 Specimen

13 13 [0] 6 Specimen

14 14 [90] 6 Specimen

15 15 [90] 6 Specimen

16 16 [45/-45] s Specimen

17 17 [45/-45] s Specimen

18 18 [45/-45] s Specimen

19 19 [45/-45] s Specimen Calculation of G 12 The shear modulus implied by these measurements is*: (Whitney, Daniels, Pipes, Experimental Mechanics of Fiber Reinforced Materials, Chapter 4, ISBN 0- 912053-01-1)

20 20 Summary of Measured Unidirectional Properties and Predictions for a [0/20/-20] s Laminate l Summary of measured unidirectional properties: E 1 = 59.5 Msi 12 = 0.39 E 2 = 0.806 Msi G 12 = 0.595 Msi l Predicted properties for a [0/20/-20] s laminate: E x = 38.4 Msi xy = 3.0 E y = 1.08 Msi G xy = 4.55 Msi

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

22 22 [0/20/-20] s Specimen (Predicted E x = 38.4 Msi)

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

24 24 Sensitivity Study Variation in E xx for [0/+  /-  ] s Laminates

25 25 Sensitivity Study Variation in xy for [0/+  /-  ] s Laminates

26 26 Sensitivity Study Variation in E yy and G xy for [0/+  /-  ] s Laminates

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


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