Volume 26, Issue 4 (July 1998)
The Applicability of ASTM Standard Test Specimens to Fracture and Fatigue Crack Growth of Discontinuous-Fiber Composites
A round-robin test program was performed to investigate the applicability of ASTM Standards E 399-90 and E 647-95a to discontinuous-fiber reinforced composite materials. Specifically, several standard test specimen geometries (the compact specimen, C(T), the bend specimen, SE(B), and the middle-tension specimen, M(T)) were investigated for use with 15 wt% SiC whisker-reinforced 2009 aluminum. E 399 fracture toughness tests showed that the compact specimen, C(T), does not provide useful data when the crack is oriented perpendicular to the whisker alignment direction (LT), Out-of-plane cracking with crack angles up to 60° was observed that resulted in invalid tests. The C(T) specimen did provide useful data when the crack was oriented parallel to the whisker alignment direction (TL). The SE(B) specimen had no problems with out-of-plane cracking and provided valid data in the E 399 tests.
The C(T) specimen was not useful in the E 647 fatigue crack growth rate tests in the LT orientation unless the specimens were side-grooved to maintain an in-plane crack. There were no problems with out-of-plane cracking in the C(T) specimen when it was used to text the TL orientation. The M(T) specimen maintained in-plane cracks and provided valid data in either the LT or the TL orientation tests.