Numerical modelling and optimization of an electronic system embedded in multi-layered viscoelastic materials under shock loads

Abstract

Presented here is the use and optimization of mutli-Iayer viscoelastic buffer materials to protect embedded electronic systems from high mechanical forces such as impacts. The test vehicle was a solid sports ball, Figure 1. The embedded system was first encapsulated using standard epoxy encapsulant, then further encapsulated with two different buffer materials (a soft and a hard rubber) before the entire system was embedded in the ball. The ball (from the Irish game of hurling) has an original polyurethane/cork core encased in a leather outer skin and is 70 mm. in diameter and weighs 11 Og. The multi-layer buffering system reduces the imposed stress on the epoxy-encapsulated embedded system, so that the stress transmitted to the electronics is significantly reduced. From this point of view, the stress experienced at the embedded system edge was taken as the objective function to be minimized within the overall constraint that the modified ball must closely retain its original size, weight and "bounce" i.e. its Coefficient of Restitution (CoR). This is a specific example of the more general embedded systems problem of embedding, say, a system such as a wireless sensor node in a material or structure without significantly changing the material or structure mechanical properties and reliability. A numerical model, using ANSYS 11.0, was developed and used in a simulation-based designed experiment of eight runs. The element SOLlD92 was used to . m ? del the plastic and electronic structures. The optImIzed multilayered structure reduced the stress on the embedded system by 50% in comparison to the original un-buffered structure and reduced stress by 25% in comparison to the non-optimized buffer system. The optimized structure was within 90% of the original one for weight and 85 % for CoR. This work has defined a design methodology for buffer layers that significantly increase the protection of embedded electronic systems from high mechanical forces without major impact on the host object mechanical properties. The methodology is particularly applicable to the mechanical design of smart objects and structures.

Influence of Microstructure on the Dynamic Behaviour of Polyurethane Foam with Various Densities

“…This is due to the nanometric scale's smaller radius of alumina than bentonite. Alumina causes a slight variation in cell orientation reverently to growth direction 10-15, and this may be due to the action of alumina for thixotropic reinforcing, which leads to a changing viscosity prerogative and an increase in the temperature during elevation [74]. Figure 18 shows the cross-section of the first and sixth polyurethane foam supports.…”