The Tsai-Wu index tells you WHEN a part fails. It doesn't tell you HOW. In this technical training we apply the Tsai-Wu and Hashin failure criteria to a 12 m × 300 daN GFRP pole (a follow-up to the structural calculation video of the same pole) and show why, in filament-wound tubular structures, that difference changes the design decision.

What you'll see:

• How combined loads (bending, shear, axial and torsion) become σ1, σ2 and τ12 stresses in each layer (micromechanics + classical laminate theory)

• Why von Mises and Tresca give false confidence in composites (FS ≈ 8.6 vs an actual R ≈ 1.92)

• Tsai-Wu: one global, interactive index, easy to code — and its limitation

• Hashin (1980): four physical modes — fiber/matrix, tension/compression

• Ply and laminate failure envelopes, and a map of the index along the height and around the tube

• Progressive failure (ply discount) up to collapse, compared with local buckling

Case-study results (critical section 0.4 m above ground, nominal load):

• Tsai-Wu: R = 1.86 → FS/R index = 0.808 with FS = 1.5 (passes)

• Hashin: first failure = matrix tension cracking in the ±88° hoop layer, R = 1.92

• Fiber rupture (±15° layers): ≈ 9.3× the nominal load

• Local wall buckling: 6.13× · progressive collapse: 8.82×

The matrix warns you; the wall and the fiber decide.

Chapters

0:00 Intro: does the pole fail? How does it fail?

0:44 guiFW said 1.027. But what broke?

1:17 Combined loads at the pole base

1:50 From tube to ply: σ1, σ2, τ12

2:25 Why von Mises gives false confidence

2:55 The Tsai-Wu criterion

3:30 The Hashin criterion: four failure modes

3:58 Ply envelopes: one ellipse vs four boundaries

4:28 Case study: critical section, layer by layer

4:54 Where it fails: along the height and around the tube

5:16 Progressive failure: from first crack to collapse

5:48 The main lesson

6:09 Laminate envelopes in the σx–τxθ plane

6:35 Design decisions that delay the first crack

7:05 What about guiFW?

7:30 Designer's checklist

Code for this video (Python): micromechanics, CLT, loads, Tsai-Wu, Hashin, progressive failure, envelopes and charts — output to JSON, CSV and a calculation report.

References

• Tsai, S. W.; Wu, E. M. A general theory of strength for anisotropic materials. J. Composite Materials, 1971.

• Hashin, Z. Failure criteria for unidirectional fiber composites. J. Applied Mechanics, 1980.

• Strength tests: ASTM D3039, D6641, D3518, D2290.

Material and load values are examples. For a real design, use strengths measured on your own material and process.

guiFW — filament winding software and G-code: https://guifw.com

#composites #GFRP #TsaiWu #Hashin #filamentwinding #structuralengineering #FRP