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

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)

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)

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

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 0-912053-01-1)

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

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

Specimen Preparation - Unidirectional Tests (Nominal) physical dimensions: [0]6 specimens: 0.0140 x 0.7450 x 7 in [90]6 specimens: 0.0140 x 0.7450 x 6 in [45/-45]s specimens: 0.0120 x 0.7450 x 6 in Comments: Nominal ply thickness was 0.0024 in for [0]6 and [90]6 specimens and 0.0030 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

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

[0]6 Specimen

[0]6 Specimen

[0]6 Specimen

[0]6 Specimen

[90]6 Specimen

[90]6 Specimen

[45/-45]s Specimen

[45/-45]s Specimen

[45/-45]s Specimen

[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 0-912053-01-1)

Summary of Measured Unidirectional Properties and Predictions for a [0/20/-20]s Laminate E1 = 59.5 Msi n12 = 0.39 E2 = 0.806 Msi G12 = 0.595 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

[0/20/-20]s Specimen

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

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

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

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

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

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