Hygrothermal influence on the interlaminar shear strength of Kevlar-graphite/epoxy hybrid composites

The hygrothermal influence on the interlaminar shear strength of Kevlar 49-graphite/epoxy hybrid composite was investigated in the temperature range –50 to 150 ° C. Moisture was introduced into the specimen by immersion in distilled water until a specified weight gain occurred. Two material lay-up were used in this investigation. In Kev 49/T-300/Kev 49, Kevlar 49 and graphite prepreg tapes were used as outer and centre layer, respectively and in T-300/Kev 49/T-300, it was vice versa. In both cases the tapes were alternated until the total thickness was achieved. The results show that interlaminar shear strength change with the ply sequence of hybrid laminates. The interlaminar shear strength of T-300/Kev 49/T-300 is relatively higher than that of Kev 49/T-300/Kev 49. The interlaminar shear strength of both T-300/Kev 49/T-300 and Kev 49/T-300/Kev 49 decrease with the increase of temperature in the range –50 to 150 ° C. The addition of moisture further degrade the interlaminar shear strength in the same temperature range. Close physical observation showed clear evidence of interlaminar shear failure for most of the specimens.