Standard Methods for Aerospace Stress Analysis

11Composite Testing Methods and Procedures

11.1 Introduction to Composite Testing Methods and Procedures

The mechanical properties and the allowable strength of laminates and honeycomb sandwich panels are the areas that will be covered in this chapter. Uniaxial and (±45) off‐axis tensile or Iosipescu tests for laminate composites will be covered here. ASTM D3039 is the standard method that would be followed for the laminate tensile testing.

Determination of the flexural and transverse (through the thickness) shear stiffness properties and their allowable strength would be discussed for flat sandwich constructions. The sandwich panel constructions would be subjected to flexure in such a manner that the applied moments produce curvature of the sandwich‐facing planes. The core material forms include those with discontinuous bonding surfaces (such as honeycomb). These methods use test results obtained per ASTM Test Methods C393/C393M or D7250/D7250M, or both.

11.2 Uniaxial Tensile Test

ASTM D3039 is the standard method that would be followed for the laminate tensile testing unidirectional laminate with fibers either oriented at 0° or 90° has to be fabricated with appropriate end‐tabs per ASTM D3039 standards. The coupons have to be pulled in uniaxial tensile test machines to failure. The slope of the applied load to head displacement data converted to a stress–strain curve is used to determine the 0° and 90° ply lamina Young’s modulus, E₁₁ and E₂₂ (Figure 11.1).

The measurement ...