Comparison of interlaminar fracture toughness between CFRP and ALFRP laminates with common epoxy matrix at 77K in LN <inf>2</inf>

Journal
European Structural Integrity Society  
Volume
32
Issue
C
Start Page
421
End Page
432
Citation
European Structural Integrity Society 32 (C): 421-432 (2003)
Publisher DOI
10.1016/S1566-1369(03)80113-9
Scopus ID
2-s2.0-77957026941
Mode I and II interlaminar fracture toughness was investigated with unidirectional carbon fiber (CF)/epoxy and alumina fiber (ALF)/epoxy laminates. A common bisphenol A type epoxy matrix was used to highlight the influence of the fiber physical and geometrical properties. The tests were carried out at 77K in liquid nitrogen (77K-LN 2 ), and the results were compared with those at room temperature in air (RT-air). The mode I fracture toughness of the neat epoxy matrix was also evaluated both in 77K-LN 2 and RT-air for comparison. The fracture toughness of the neat resin increased by 1.8 times by changing the test environment from RT-air to 77K-LN 2 . This increase was directly translated into the increase of the mode I fracture toughness values of ALF/epoxy where the toughness in 77K-LN 2 was 1.8 times higher than that in RT-air. This environmental effect for CF/epoxy laminates was smaller and the toughness in 77K-LN 2 was only 1.3 times higher than that in RT-air. On the other hand, the mode II interlaminar fracture toughness values of both CF and ALF/epoxy laminates were insensitive to the test environment. The ratios of the fracture toughness of ALF/epoxy to those of CF/epoxy were about two for both laminates in 77K-LN 2 and RT-air. The mechanism of the fiber and environmental effects were discussed from the mesoscopic view points on the bases of microscopic observation.
Subjects
Alumina fiber
Carbon fiber
Epoxy matrix
Interlaminar fracture toughness
Liquid nitrogen