In structural strengthening, CFRP is typically applied as externally bonded sheets or laminates to concrete, steel, or masonry substrates. The primary function of the CFRP is to carry tensile loads—resisting bending moments, shear forces, or axial stresses. Therefore, tensile strength and modulus are the two most critical mechanical properties governing design.

ASTM D3039 directly measures:

• Ultimate tensile strength (the maximum stress the material can withstand before failure),

• Tensile modulus of elasticity (stiffness under load),

• Failure strain (ductility or brittleness),

• Poisson’s ratio (lateral contraction behavior).

Complementary ASTM Standards in Structural Strengthening

While ASTM D3039 is the most meaningful single test, it is often used alongside other standards to form a complete characterization:

ASTM D7264/D7264M: Flexural properties (relevant for beam strengthening).

ASTM D5573: Qualification of adhesives used to bond CFRP to concrete.

ACI 440.3R-referenced pull-off tests (often based on ASTM D429 or modified versions): Interfacial bond strength between CFRP and substrate.

ASTM C1609: For hybrid systems involving cementitious matrices.

However, none of these replace the fundamental need for tensile property data. Without ASTM D3039, there is no baseline for material performance.