Protection Of Embedded Systems For Applications Involving High Loading Rate Mechanical Forces

"This thesis describes the development of a methodology to optimise the dimensions and mechanical properties of force-absorbing layers surrounding miniaturised embedded electronic modules subject to high mechanical compressive/impact forces and vibration. While much has been published on the mechanical protection of electronic systems in larger scale applications, where traditional mechanical shock absorbers and springs can be used to protect the electronics, little has been published on the mechanical protection of miniature electronic modules embedded in smart structures and materials where traditional methods of mechanical protection are not feasible. The generalised system concept used in this thesis is of module encapsulation in a multilayer of rubber-like materials to net as a mechanical buffer. This meant that it was necessary to model and optimise a multilayer combination of soft/hard rubber-like materials and its geometries subject to a set of external constraints. To drive the research a challenging test vehicle was chosen - a sliotar containing sensing electronics. This posed considerable challenges of small size and strict constraints on final weight and mechanical properties - a situation very typical of a smart object where it is necessary to maintain the object's original size, weight and mechanical properties. To optimise the electronic protection, it was necessary to understand the complete impact system, i.e. the sliotar-hurley impact), again this is typical of a smart object scenario where the time-dependent variables of the impact system are needed to understand the object's interactions. Analysing the sliotar-hurley impact however presented many challenges from mechanical point-of-view which lead to a number of novel contributions to the state of the art, including (I) highly nonlinear materials characterisation and modelling and at low and high strain-rate loading conditions for hurling materials, (2) analytical studies and modelling to describe the impact of the ""structures"" (sliotar and hurley) analytically and to extract the coefficient of restitution (CoR) of the sliotar as a function of impact speed, (3) transient finite element analyses of highly nonlinear structures and materials under different mechanical loads, and (4) experimental validation of the developed models. Based on these analyses and models, a multilayer rubber buffer structure was designed and optimised to surround and protect an electronic module embedded in a sliotar subject to high static and dynamic mechanical forces while meeting constraints on sliotar size, weight, and mechanical properties. The final result was a 73% and 84% reduction in dynamic and static mechanical forces, respectively, on the embedded electronics. This novel contribution has put in place a methodology for design of property-constrained smart objects with embedded electronics protected from high mechanical forces using multilayer rubber buffer materials."