### Calculator Cored Laminate Composite Stiffness Equations

Cored Laminate Composite Stiffness Equations and Calculator

In the development of formulas for deflection, stresses , and buckling of sandwich components, mathematical expressions for bending, extensional, and shear stiffness often appear as do parameters involving these stiffnesses. It is convenient to present the fundamental stiffness formulas at the outset. Here also are discussed the effects of facing and core stiffness on sandwich bending stiffness so that the degree of approximation implied by simplified formulas neglecting facing and core stiffness is known.

For more detail information see: Structural Sandwich Composites Design Manual A structural sandwich under forces normal to its facings has a bending stiffness, per unit width, given by the equation:

Where:

Sandwich Bending Stiffness:

The extensional stiffness of a sandwich, stretched or compressed by force in its plane, is given by the formula.

D = Bending Stiffness, lb-in2

Click on image below to enlarge E'n is the effective modulus of elasticity of facing, psi

E'c is effective core elastic modulus in the appropriate L or W direction, psi

Vn= Poissons Ratio

VnC= Poissons Ratio, Core 1 and 2 are subscripts denoting facing 1 and 2

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References: MIL-HDBK-23