Fracture toughness (K Q ) testing with a mini‐compact tension (CT) specimen

A testing method using the Rheometrics Mechanical Spectrometer as the loading instrument to measure the fracture toughness K Q , which is related to a specific sample geometry and dimensions (half‐inch compact tension) is reported. The small sample size requirement makes it attractive to do fracture toughness testing on newly synthesized material for preliminary material study and comparison purposes. Commercially available epoxy resins were used to check the procedure at different temperatures (−150° to 250°C). An empirical crack length averaging method was used that appears to give constant K Q values independent of the a/W ratio values. The fracture surfaces were studied using scanning electron microscopy.