Chapter7

Chapter 7: Experimental Characterization of Composite Materials Objectives of Experimental Study: • Determine properties of unidirectional lamina for use in structural design & analysis. • Investigate & verify the analytical prediction of the mechanical behavior of structure. • Independent experimental study of material and structural behavior for specific geometry & loading conditions. Specific Testing: • Characterization of constituent materials. • Characterization of unidirectional lamina. - Physical: Density, Volume fraction, Porosity, CTE & CME - Mechanical: E1, E2, ν12, and G12. • Determination of interlaminar properties. • Determination of material properties under special loading types; fatigue, creep, impact, high loading, etc. • Experimental stress and failure analysis of composite laminates & structures. • Assessment of structural integrity by nondestructive testing. Ref: ASTM standards on Testing and Materials-Vol. 15.3) D30 High modulus composite materials. MIL Handbook

Determination of Tensile Properties

E1 =

∆σ 1 ∆ε1

ν 12 = −

E2 =

∆σ 2 ∆ε 2

ν 21 = − 0-deg 90-deg Laminates

∆ε 2 ∆ε1

∆ε1 ∆ε 2

Determination of Compressive Properties

E1c =

∆σ 1 ∆ε1

ν 12 c = −

∆ε 2 ∆ε1

Determination of Shear Properties

∆τ 6 = (±45)ns angle-ply laminate

∆σ x 2

G12 =

(

∆γ 6 = ∆ε x − ∆ε y

∆σ x 2 ∆ε x − ∆ε y

(

)

)

Iosipescu Shear Test x1 Shear modulus G13

x3 x2 Shear modulus G12

x1 Schematic of the loading fixture

x2

P τ6 = lh ∆γ 6 = ( ∆ε 45 − ∆ε −45 ) G12 =

∆τ 6 ∆γ 6

Shear modulus G23

x3