The loss coefficient-modulus \((\eta-E)\) chart of Figure 3.9 is populated only along one diagonal band. (The loss coefficient \(\eta\) measures the fraction of the elastic energy that is dissipated during a load-unload cycle.) Monolithic materials with low \(E\) have high \(\eta\), those with high \(E\) have low \(\eta\). The challenge here is to devise hybrids to fill the holes, with the following applications in mind.

a. Sheet steel (as used in car body panels, for instance) is prone to lightly damped flexural vibration. Devise a hybrid sheet that combines the high stiffness, \(E\), of steel with high loss coefficient, \(\eta\).

b. High loss coefficient means that energy is dissipated on mechanical cycling. This energy appears as heat, sometimes with undesirable consequences. Devise a hybrid with low modulus \(E\) and low loss coefficient, \(\eta\).

Data From Figure 3.9

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Loss coefficient, 77, at 30C 10 Neoprene Butyl rubber Elastomers Isoprene Silicone elastomers 10-1 Flexible polymer foams Foams 10-2 10-3 10-4 10-5 E=0 =0.04 GPa Polyurethane E Leather Loss coefficient - modulus lonomers Polymers Lead alloys PP ABS Concrete Epoxies Brick Wood Cork Rigid polymer foams PC PMMA PET 10-3 10-2 10-1 Nontechnical ceramics Stone Composites GFRP Zinc alloys Al alloys Technical Cu alloys Mg alloys Metals Ti alloys CFRP Cast irons Steels W alloys Al2O3 WC ceramics Soda glass Silica glass SigNa 10 100 1000 Young's modulus, E (GPa).