Define laminate mid-plane strain.

Define laminate mid-plane strain.

• A. The average in-plane strain at the laminate mid-plane under load.
• B. The maximum in-plane strain in the laminate.
• C. The transverse strain at the mid-plane.
• D. The average out-of-plane strain at the mid-plane.

Answer: (A)

In laminated plates, the in-plane strain varies through the thickness, but we describe the in-plane deformation of the plate using the mid-surface values. Classical laminate theory expresses the in-plane strains through thickness as ε(z) = ε0 + zκ, where ε0 is the strain state at the mid-plane (z = 0). So the laminate mid-plane strain is the in-plane strain components right at the mid-surface of the laminate. It represents the deformation of the mid-surface in the plane of the plate under load. It is not the maximum in-plane strain through the thickness, nor the transverse (out-of-plane) strain, nor an out-of-plane average.

In laminated plates, the in-plane strain varies through the thickness, but we describe the in-plane deformation of the plate using the mid-surface values. Classical laminate theory expresses the in-plane strains through thickness as ε(z) = ε0 + zκ, where ε0 is the strain state at the mid-plane (z = 0). So the laminate mid-plane strain is the in-plane strain components right at the mid-surface of the laminate. It represents the deformation of the mid-surface in the plane of the plate under load. It is not the maximum in-plane strain through the thickness, nor the transverse (out-of-plane) strain, nor an out-of-plane average.