1. What is meant by toughness? How does it differ from strength?
2. Why is there a transition from ductile to brittle behavior at a transition crack length, ccrit?
3. A tensile sample of width 10mm contains an internal crack of length 0.3mm. When loaded in tension the crack suddenly propagates when the stress reaches 450 MPa. What is the fracture toughness K1c of the material of the sample? If the material has a modulus E of 200 GPa, what is its toughness? (Assume Y =1)
4. Use the K1c - E chart of Figure 8.8 to establish:
-Whether CFRP has higher fracture toughness K1c than aluminum alloys.
-Whether Polypropylene (PP) has a higher toughness Gc than aluminum alloys
-Whether Polycarbonate (PC) has a higher fracture toughness K1c than glass.