A Comprehensive Study on Sublaminate Crack Growth Stability and Its Effects on the Load-Carrying Capacity.
Final rept. 1 Oct 81-30 Sep 83,
DREXEL UNIV PHILADELPHIA PA DEPT OF MECHANICAL ENGINEERING AND MECHANICS
Pagination or Media Count:
This report highlights the development of a unified method for the formation mechanisms of matrix-dominated cracks in a class of structural laminates that are made using unidirectionally fiber reinforced composite plies. Because of the collimated reinforcement structure exhibited in this class of laminates, the growth of an individual matrix crack is confined either in the fiber-matrix interface or in the ply-to-ply interface. The former occurs as intraply crack caused by primarily by in-ply stresses, while the latter occurs as interply crack caused by interlaminar stresses. These are the two fundamental modes exhibited in matrix cracking. Experiments using graphite-epoxy composite systems have established that matrix cracking is actually a process in which a great number of similar cracks occur during the course of loading. The multiplicity in the crack formation process stems from the existence of material flaws which distribute randomly throughout the laminate, and from the internal reinforcement structure which inhibits individual crack from growing into large proportions. When viewed at the ply level, growth of a matrix crack is essentially brittle in nature its growth path initially follows one of the two fundamental modes. When blunted, the initial mode may turn to the other mode. Thus, the individual growth path may be considered as piece-wise self-similar.
- Laminates and Composite Materials