Static and fatigue behavior of double-double glass/epoxy laminates

Double-double (DD) configuration has been proposed as a new concept in which a double set of double helix [±ϕ/± ψ] n angles are stacked up to form a composite laminate. This concept promises significant advantages over conventional layups for composite design optimization and manufacturing. This experimental study evaluated the performance of two elastically in-plane equivalent glass/epoxy laminates suited for wind turbine blade applications: a quadriaxial (Quad) [±45/(0/90) 3 ] s and a double-double (DD) [±15/±75] 4T . Mechanical tests were performed under cyclic uniaxial tensile-tensile load using unnotched and open hole specimens. Delamination initiating from the free edges resulted in premature failure of the unnotched DD specimens. For open hole specimens, fatigue tests results obtained from both stacking sequences showed similar performance. Ultimately, the study presented constitutes a valuable contribution to the understanding of fatigue behavior of double-double glass/epoxy laminates subjected to tensile cyclic loading.