Static and dynamic axial loading of a partially debonded fiber

Abstract

The stresses on a partially bonded fiber in a composite material subject to axial loads are derived for both static and dynamic conditions. The static stress intensity is calculated for a fiber which is only partially bonded circumferentially and subject to a constant axial stress gradient, i.e. a uniform axial body force. The same configuration of a single partially bonded fiber is then considered for loading in the form of a dynamic stress gradient in the fiber, and particular attention is given to the stress intensity factor at the edge of the bond when the fiber is subject to a step load. The numerical results show that the dynamic stress always overshoots the static value, and the time taken to achieve the static equilibrium stress can be quite long if the fiber is nearly debonded. This is related to the phenomenon that a very loosely bonded fiber may resonate strongly at a frequency which goes to zero as the size of the bond vanishes.