Compression-After-Impact Example

A worked example showing how delamination size and sublaminate thickness affect the CAI strength through sublaminate buckling.

Advanced Damage & Failure5 min read

worked exampleCAIcompression after impactsublaminate bucklingdelaminationresidual strength

Problem

A 4 mm thick composite laminate has a mid-plane delamination of 30 mm diameter from impact. The undamaged compression strength is 500 MPa. Estimate the CAI strength reduction from sublaminate buckling.

Given

t = 4 mm (total thickness)
Delamination at mid-plane → t_sub = 2 mm
Delamination diameter = 30 mm (L = 15 mm half-span)
Undamaged σ_c = 500 MPa
All values illustrative

Solution

Sublaminate buckling stress (simplified):

σ_cr,sub / σ_cr,intact = (t_sub / t)² = (2/4)² = 0.25

The sublaminate buckles at 25% of the
intact buckling stress.

If intact compression strength = 500 MPa:
  Estimated CAI ≈ 500 × 0.25 = 125 MPa
  (Simplified estimate — actual CAI depends
on delamination shape, growth, and fibre failure)

CAI retention = 125/500 = 25%

Actual CAI is typically higher than this
simple estimate because of post-buckling
reserve and boundary constraint.

Values are illustrative — do NOT use for design.