Fracture toughness of TiB2 and B4C using the single-edge precracked beam, indentation strength, chevron notched beam, an indentation strength methods

The mode I fracture toughness (KIc) of boron carbide (B4C) and titanium diboride (TiB2) was determined using four competing techniques. The indentation strength (IS), chevron notched beam (CNB), and indentation fracture (IF) methods are common techniques that were compared to the recently standardized single-edge precrack beam (SEPB) method. The SEPB method was more difficult to apply, but it represent the most rigorous method for KIc determination, because it uses few assumptions and requires a direct measurement of crack length. The IS method was an expeditious and economical alternative when low indentation loads were used. CNB KIc values were virtually rate-independent when displacement rates less than or equal to 0.5 mm/min were used. The IF method was the least satisfactory technique, because of high variability in Kc values and because of the low differentiation between the two materials studied