Axial strain redistribution resulting from off-axis ply cracking in polymer composites

摘要

The initial mode of damage in multidirectional composites is the accumulation of matrix cracks in the off-axis plies. Remote laser Raman spectroscopy, using aramid (Kevlar 49(R)) fibers as Raman strain sensors, has been employed to monitor the local strains in cracked crossply composites. The strain magnification in the 0degrees ply caused by 90degrees matrix cracking are measured at different levels of loading. A relationship between the values of strain magnification and the distance between the position of the fibers sensors vis-a-vis the crack front has been established. The effect of damage progression within the 0degrees plies on the remaining/surviving glass fibers is modeled satisfactorily and verified against predictions on the basis of a generalized plane strain model by assuming that the 90degrees ply "expands" in relative size against the 0degrees ply thickness. (C) 2004 American Institute of Physics.