Influence of Oxidation Temperature on the Tensile Behaviour in a 2.5 D Needled Carbon/Carbon Composite for Aircraft Brakes

An air-oxidized carbon/carbon (c/c) composite was studied under tensile conditions to examine oxidation temperature’s influence on its behaviour and on the residual mechanical properties. Three oxidation temperatures were tested with oxidation duration chosen to obtain the same weight loss on the samples at each temperature. Notable differences were found in the material’s behaviour depending on the oxidation temperatures. These results show that the weight loss criterion commonly used in the literature to quantify c/c composite oxidation needs to be complete to reflect the actual state of the material after oxidation. Microscopic observations revealed different oxidation patterns that underlined a heterogeneous consumption of the material from one temperature to another. Consequently, a non-destructive-test based on ultrasonic signals was explored in order to complete the weight loss criterion. Variations of weight loss at each exposure oxidation temperature were correctly assessed, and the technique was able to discriminate the oxidation temperatures above 5% of weight loss. The low-temperature oxidation behaviour is discussed and an explanation based on a variation on the attack of the fibre/matrix interfaces that could explain the difference of the tensile behaviour is proposed.