Hygrothermal aging properties of RTM composites toughened by polyamide nonwoven fabric

The polyamide nonwoven fabric (PNF) was chosen as structural toughening layer, and carbon fiber reinforced epoxy composites toughened by interlaminar PNF (U3160-PNF/3266) were fabricated by resin transfer molding (RTM) process. The moisture absorption properties of U3160-PNF/3266 composites and the influence of hygrothermal aging on heat resistant performance of it were investigated. The results indicate that composites have similar moisture absorption dynamics characteristics before and after toughening. But the moisture absorption rate of U3160-PNF/3266 composites is much larger at the original moisture absorption. The saturated moisture absorption rate of U3160-PNF/3266 composites is 0.96%, which is a little greater than that of untoughened composites (U3160/3266) of 0.87%. The glass transition temperatures of the two composites both decrease with the increment of hygrothermal aging time, and are going to be stable as the moisture absorption rate saturate. Up to the saturated moisture absorption, the glass transition temperatures of U3160-PNF/3266 and U3160/3266 composites are reduced by approximately 15% and 14% respectively.