The critical energy release rate was identified on 3D woven carbon/epoxy composites, using CT and SENB specimens. The analysis relied on multiple instrumentation methods to monitor the crack growth and compared several methods for the crack detection and estimation in order to obtain a robust process. Variation of with the specimen size and shape was highlighted. A non-linear framework was then proposed to describe fracture propagation in the material, relying on the existence of an internal length. The use of at least two material parameters , an asymptotic fracture release rate, and , a characteristic internal length, is necessary to completely describes the variation of the apparent with the specimen shape and scale. The use of non-linear models introducing internal lengths and controlling the dissipated energy is then investigated to transcribe the experimental results.