Direct in situ measurements of bridging stresses in CFCCs

The macro- and micro-mechanics of large scale bridging in SiC/MAS-L composites were assessed by tensile testing of DEN specimens with in situ LRM measurements. The macromechanical behavior was analyzed in terms of crack growth resistance and bridging laws using an elastic displacement correction approach. A dedicated Raman calibration curve was established for the specific composite fiber, which served in the transformation of wavenumber shifts collected from bridging fibers in the composite to bridging strain, and to stress via the elastic modulus of the fibers. Bridging strain profiles were established along the ligament of the specimen and their shape was discussed in conjunction with local notch effects. Actual bridging strain values up to 0.8% were calculated which compared well with their macromechanical counterparts within the intact-fiber regime. The individual contributions of intact and pulled-out fibers to the total fracture behavior of the composite were distinguished and are discussed in the article.