Synopsis

Determines the buckling loads and strain energy release rates for an elliptical critical flaw under a specified load. Buckling under compressive loading is one of the drivers for selecting critical flaw sizes. Plates are assumed to have clamped boundary conditions and an elliptical shape. The total thickness of the laminate corresponds to an assumed depth of the delamination.

The calculation is based on: Flanagan, G.,"Two-Dimensional Delamination Growth in Composite Laminates Under Compression Loading", Composite Materials: Testing and Design (Eighth Conference) ASTM STP 972J.D. Whitcomb Editor, American Society for Testing and Materials, Philadephia, 1988, pp. 180-190.

Notes

• Derivation of buckling solution
• For an unsymmetric laminate, the code uses a reduced bending stiffness, defined at Dr=D-Tranpose[B].Inverse[A].B
• The buckling calculation uses an approximation that includes the effect of shear strain in the base laminate. The SERR calculation does not include shear. The user may wish to reorient the problem into principal strain coordinates.

Input

Properties of delaminated sublaminated

Enter the layer material properties as a list {Ex, Ey, Gxy, nuxy}:

Enter a stacking sequence {theta1, theta2, ...}: Help on advanced stack entry

Enter the default per-ply thickness

Enter the length of the half ellipse axis along x (major axis)

Enter the length of the half ellipse axis along y (minor axis)

Enter the base laminate strains (in/in) {epsilon x, epsilon y, gamma xy}:

Results

Buckling Strains:

Strain Energy Release Rates:

Plots of SERR with fixed ellipse width and height

Red Curve:Growth in x direction, Blue Curve:Growth in y direction