Ok, so I have been giving myself a crash course in vibration damping properties for composite materials and I’ve come up with a stumper (at least for me). Lets say you have a simple sandwich layup of carbon uni on either side of a foam core which is cantilevered and vibrated like a tuning fork. Now you add a damping sheet into the mix (say woven polypropylene with miraculously no bonding problems). You can place the damping layer either between the carbon facings and the core OR on the outside faces of the carbon. Intuitively it seems as if between facings and core would be more effective as it isolates the carbon facings from the core and therefore from each other by acting as shearing layers. However, from an energy-lost perspective it seems like the damping layers being furthest from the neutral axis would be most effective as they would need to strain the most and therefore have the greatest energy losses.
Anyone have a better understanding of all this than I do? My research into calculating vibrations in composites produced lots of conflicting theories and not a lot of basic conceptual discussions which is what I need.