Is the fracture toughness, \(K_{l c}\), of the common polymers polycarbonate, \(\mathrm{ABS}\), or polystyrene larger or smaller than the engineering ceramic alumina, \(\mathrm{Al}_{2} \mathrm{O}_{3}\) ? Are their toughness qualities \(G_{1 c}=K_{1 c}^{2} / E\) larger or smaller? The \(K_{l c}-E\) chart, Fig. 3.7, will help.

Fig. 3.7

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1000 Fracture toughness - modulus 100 Design guidelines Fracture toughness, Kc (MPa.m1/2) 10 Metals Zinc alloys Composites Al alloys, Mg alloys Natural materials Lead alloys Leather PP PC Wood ABS- KJE Polymers KJE Elastomers EVA Polyurethane Silicone Ionomers elastomers Buty PTFE rubber 0.1 0.01 Prietaire polymer foams 0.001 Cork 0.01 0.1 Toughness G = kJ/m Cu alloys Ni alloys Steels Ti alloys OW alloys 100 10 Cast icens 0.1 Diamond SIGN SIC WC 0001 GFRP CFRP Brick Al2O3 Silicon 0.001 Stone Soda Saica Epoxies- Concrete Technical ceramics Nontechnical ceramics Foams Rigid polymer foams Lower limit for K MFA 15 10 100 1000 Young's modulus, E (GPa)