The non-dimensional design strategy for double-double laminates under shear: The off-the-shelf prepreg approach

Abstract

A novel buckling design strategy for double-double (DD) laminates under in-plane shear loading has been developed, employing an off-the-shelf approach to enhance the applicability of DD configurations in aeronautical main structures. This strategy relies on four key components: Tsai’s modulus, the Master-Ply concept, the $D_{22\hspace{0.17em}}^{*}$ maximization criterion, and a homogenization procedure tailored for commercially available unidirectional (0°, 90°) and angle-ply (±30°, ±45°, ±60°) carbon/epoxy prepregs. Finite element analysis (FEA) was used to validate analytical predictions for long/infinite composite plates under two primary boundary conditions: simply supported and clamped edges. From a design standpoint, increasing the number of sub-laminate repetitions [±ψ/±ϕ]_rT effectively reduces bend-twist coupling effects $\left(D_{16}^{*},D_{26}^{*}\right)$ in DD laminates. Simultaneously, the bending stiffness components $\left(D_{11}^{*},D_{22}^{*},D_{12}^{*},D_{66}^{*}\right)$ increase by nearly an order of magnitude when the laminate thickness is doubled. Among the 13 DD configurations analyzed, those with smaller angles, such as [±0/±30]₄ and [±0/±45]₄, exhibit the lowest critical buckling loads under in-plane shear loading. However, configurations like [±0/±45]₄ and [±30/±30]₄ outperform the benchmark case [03/±452/90]_s by 45.56% and 44.27%, respectively. A clear trend emerges: increasing the angle orientation reduces the half-wavelength of buckling, leading to higher critical loads. The top-performing DD configuration, [±60/±60]₄, achieves a buckling load nearly double that of the benchmark case—an improvement of approximately 185%.