What does G_IC measure?

What does G_IC measure?

• A. The critical energy release rate for Mode II delamination, a measure of resistance to crack growth in shear.
• B. The critical energy release rate for Mode I delamination, a measure of resistance to crack growth in opening mode.
• C. The shear modulus of the matrix.
• D. The density of the composite.

Answer: (B)

G_IC measures the resistance to delamination under opening mode. In laminated composites, delamination can propagate as the crack faces move apart (Mode I), slide in plane (Mode II), or tear out of the plane (Mode III). G_IC is the critical energy release rate for Mode I, meaning the amount of energy per area needed to advance a crack when it opens perpendicularly to the crack plane. It reflects how tough the material is against crack growth in opening mode. It is not a measure of shear resistance (that would relate to Mode II, often denoted G_IIC or similar), nor a stiffness property like the shear modulus, nor a density property of the composite.

G_IC measures the resistance to delamination under opening mode. In laminated composites, delamination can propagate as the crack faces move apart (Mode I), slide in plane (Mode II), or tear out of the plane (Mode III). G_IC is the critical energy release rate for Mode I, meaning the amount of energy per area needed to advance a crack when it opens perpendicularly to the crack plane. It reflects how tough the material is against crack growth in opening mode. It is not a measure of shear resistance (that would relate to Mode II, often denoted G_IIC or similar), nor a stiffness property like the shear modulus, nor a density property of the composite.