I never said that the material you use for a harmonic damper and a shock abosorber are going to be the same, I was just pointing out that there is a difference between a spring and a damper. A spring stores energy and returns it, while a damper absorbs energy and dissipates it. If you take something that absorbs energy (like lead) and whack at it with a hammer it will get hot, since the energy is being absorbed and not returned.