Failure characteristics of carbon/BMI-Nomex sandwich joints in various hygrothermal conditions

An experimental study has been conducted to investigate the effects of elevated temperature and humidity on the strength and failure mode of carbon/BMI-Nomex composite sandwich joints. Pull-out and shear tests were performed under three different humidity conditions (dry, pre-saturation, and full saturation) and five different temperature conditions (−55, 24, 82, 177, and 204 °C). With respect to pull-out loading, while the ultimate failure modes were diverse in accordance with the environmental conditions, the initial damage to the joints was always due to core shear buckling. In the joints under shear loading, the bearing failure of the upper face by the insert flange and insert separation from the potting mass commonly occurred as the main failure modes under every environmental condition. The pull-out and shear strengths of the sandwich joints at the coldest temperature (−55 °C) in the dry condition always showed the highest values among all conditions.