Longitudinal Tensile Strength (σ_L) Calculator

What is Longitudinal Tensile Strength (σ_L)?

Longitudinal tensile strength (σ_L) is the maximum stress a unidirectional composite can withstand when loaded parallel to the fiber direction. It is the most critical structural property for high-performance composites, as fibers carry ~90% of the load in this orientation.

Calculation Formula (Rule of Mixtures for Longitudinal Strength)

Where (use consistent units: MPa or ksi):
• σ_f = Fiber tensile strength
• V_f = Fiber volume fraction (0–1)
• σ_m' = Matrix stress at fiber failure strain (not ultimate matrix strength)

Enter Values

Fiber Tensile Strength σ_f (MPa or ksi) Fiber Volume Fraction Vf (0–1) Matrix Stress at Fiber Failure σ_m' (MPa or ksi) Calculate σ_L

Typical Real-World Example

T700 Carbon Fiber/Epoxy Prepreg (aerospace/wind energy standard):
σ_f = 4900 MPa, Vf = 0.60, σ_m' = 40 MPa → σ_L ≈ 2956 MPa (429 ksi).

Applications in Engineering

• Primary structural design for commercial aircraft, spacecraft, and drones
• Wind turbine blade spar cap and structural component analysis
• Automotive lightweight composite part optimization (chassis, body panels)
• High-performance sporting goods design (bicycle frames, tennis rackets, golf clubs)
• Marine composite structure engineering (boat hulls, masts)