MMF-based Failure Initiation and Progression for Hybrid Composite Materials

Micromechanics of failure (MMF) is a new approach that links strength and life of fiber, matrix and their interfaces to those of plies, laminates and structures. Use of MMF for static strength and its extension to creep rupture and fatigue life prediction already show great promise. MMF for this proposal will be extended to interlaminar hybrids like Tigr and Glare, but also many structural details such as Pi- and T-joints, bonded joints, and toughened epoxy by addition of thermoplastic particles. Initiation of failure, subsequent propagation and eventual failure due to arbitrary load history will be cast in an internally consistent framework of MMF. This approach is generic, not a point design, and does not need knock down factors. This is fundamentally different from many prevailing ply-based failure criteria and empirical approaches that rely completely on testing and more testing. MMF is based on first principles of physics (micromechanics) and chemistry (interfacial strength and time/temperature superposition) so validation of analytic predictions can be accomplished by specifically designed experiments. The application of MMF to hybrid composites for this program is a natural extension. Far-reaching results can be expected and ready to be fed into a reliability theory in Phase II.