The aim of this study is the investigation of the link between the elaboration process, the microstructure and the acoustic behaviour of silicone foams obtained using a two-component silicone. Different parameters are varied such as the ratio of components, the addition of a thinning agent and the curing temperature, with the objective of understanding the influence of each parameter in the foam's acoustic absorption. The microstructure is analysed using SEM and acoustic properties are measured. Two non-acoustical properties of the porous material are also investigated, namely the porosity and the flow resistivity. Pore cell size and interconnected porosity have great impact on acoustical properties. Significant enhancements of the absorption properties could be obtained in the low frequency band by increasing the rate of agent B through an increase in the amount of interconnected porous cells. An improvement in absorption is observed in the higher frequency range when a thinning agent is added to the mixture. Representative models of the foam for acoustic simulations are obtained allowing estimation of the tortuosity, viscous and thermal characteristic length from acoustic measurements. These models are able to simulate the acoustic behaviour of the silicone foams when embedded in sound packages.
This chapter is dedicated to the Dynamical Mechanical Thermal Analysis of Shape Memory Polymers. Temperature obviously plays a major role in the mechanical properties of these materials, hence the understanding of the physical phenomena driving the shape memory effect is of first importance for the design of practical applications in which Shape Memory Polymers are used. The Shape Memory effect being closely related to the viscoelastic behavior of the polymer, it is important to properly describe it with appropriate tools. The objective of this chapter is to describe characterization methods, models and parameters identification techniques that can be easily used for the description of the thermo-mechanical behavior of SMPs. The associated models can easily be implemented in finite element codes for time or frequency domain simulations. The experimental results and all numerical values of the models are provided for three Shape Memory Polymers: the tBA/PEGDMA and a Vitrimer, which can easily be manufactured according to the data provided in open literature, and a Shape Memory Polymer filament for 3D printing, which is available on the shelf.
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