What is Longitudinal Compressive Strength (σ_CL)?

Longitudinal compressive strength (σ_CL) is the maximum compressive stress a unidirectional composite can withstand when loaded parallel to the fiber direction. Failure is dominated by fiber microbuckling, matrix shear behavior and initial fiber misalignment.

Calculation Formula (Budiansky-Fleck Model)

σ_CL = (Gₘ / (1 − Vբ)) × (1 / (1 + φ / γᵧ))

Where (use consistent units: MPa or ksi):
• Gₘ = Matrix shear modulus
• Vբ = Fiber volume fraction (0–1)
• φ = Initial fiber misalignment angle
• γᵧ = Matrix shear yield strain

Enter Values

Matrix Shear Modulus Gₘ (MPa or ksi) Fiber Volume Fraction Vf (0–1) Initial Fiber Misalignment Angle φ (degrees) Matrix Shear Yield Strain γᵧ

σ_CL = ?

Typical Real-World Example

T700 Carbon Fiber/Epoxy Prepreg (aerospace/wind energy standard):
Gₘ = 1250 MPa, Vf = 0.60, φ = 2.0°, γᵧ = 0.03 → σ_CL ≈ 1444 MPa (209 ksi).

Applications in Engineering

Compression structural design for commercial aircraft, spacecraft, and drones
Wind turbine blade spar cap compression failure analysis
Automotive composite structural component compression optimization
High-performance sporting goods compression design
Marine composite structure compression engineering

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