Development of practical semi-empirically and statistically-based equations for predicting the static and dynamic buckling capacities of 3D fibre-metal laminates

A new class of three-dimensional fibre-metal laminates (3D-FMLs) was introduced recently. It offers exemplary performance compared to 2D-FML and laminated composites counterparts, especially when impact loading is of concern. However, similarly to all slender laminate composites, this hybrid composite is also susceptible to buckling and delamination when subjected to in-plane axial loadings, especially if the load is applied suddenly (impact). This is because of the inherent nature and relatively weak interlaminar strength of laminated composites. Moreover, there exist no design equations for establishing the buckling capacity of 3D-FMLs. Therefore, a set of simple semi-empirical equations is developed and proposed to aid practicing engineers to quickly and reliably evaluate the static and dynamic buckling capacities of slender 3D-FML components. The equations are developed by adjusting Euler's buckling equations to account for the complex 3D-sandwich nature of 3D-FMLs and their inherent initial geometric imperfection, length, and the applied energy. Moreover, a statistical approach is utilized to develop a simple equation for establishing the impact buckling capacity of 3D-FMLs. The approach is based on the Face Centred Central Composite Design (FCCCD), used to produce also a simple and practical regression-based equation for evaluating the impact buckling capacity.