Lattice cores for high performance sandwich composite structures

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Sandwich panels are employed in a wide range of engineering applications, especially in the aerospace and automotive sectors, to replace traditional bulk materials whenever structural mass is a critical performance metric. Notably, cellular cores provide a unique combination of properties to sandwich panels, including high specific stiffness and high specific strength, as well as low thermal conductivity, which makes them ideal for load-bearing, thermal insulation and energy-absorbing functions. The mechanical performance of the core strongly depends on the deformation "mode", i.e. bending versus stretching, of the cell walls. Cores with cell walls undergoing axial stretching can be ten times stiffer than those deforming primarily through wall bending or buckling for the same relative density. The aim of this PhD project is to investigate the feasibility of inducing stretch-dominated behaviour in lattices via the introduction of multi-material joints and flexural hinges in the core unit cell. This project will provide a novel and flexible method for tailoring specific stiffness, strength and thermal properties beyond what can be achieved by acting upon the topology of the unit cell alone. The properties of these novel cores will be explored both numerically, via high-fidelity finite element analysis, and experimentally, employing additive manufacturing methods to build prototypes. The key objectives of this project are: - Development of high-fidelity finite element models to understand the elastic, inelastic and thermal response of lattice cores at the unit cell and assembly levels. - Optimisation of topology and multi-material hinged configurations to maximise the performance through parametric modelling. - Additive manufacturing initial prototypes of the optimised lattice cores. - Assessing the manufacturability in an efficient and robust fashion. - Testing the prototype structures and evaluate the results against the finite element analysis simulations.