Paper number 452

THE NEW ACTION PLANE RELATED STRENGTH CRITERION IN COMPARISON WITH COMMON STRENGTH CRITERIA

J. Kopp, W. Michaeli

Institute of Plastics Processing (IKV) RWTH Aachen, 52056 Aachen, Germany

Summary

Inter fibre fracture (IFF) of UD-laminae with polymer matrix is governed by the stresses ?n, ?nt, ?n1 on the fracture plane, which can be found as the plane with the highest stress exposure factor calculated from a (?n, ?nt, ?n1)-strength criterion by Puck. For visualisation a given (?2, ?3, ?23, ?31, ?21)-fracture condition is rewritten as a (?II, ?III, ??1, ??)-fracture condition, wherein ?II and ?III are the 'transverse principal stresses' and ??1 is the longitudinal shear stress resulting from ?31 and ?21 while ??is the deviation angle between the action planes of ?II and ??1. The fracture body of Puck's criterion shows a distinct influence of ??in the (?II, ?III, ??1)-space, whereas classical IFF-criteria as the Tsai,Wu- or the Hashin-criterion do not exhibit any influence of this parameter. In order to avoid the search of the fracture plane several attempts have been made to develop approximations of the (?n, ?nt, ?n1)-strength criterion by direct invariant formulations in (?2, ?3, ?23, ?31, ?21), which are investigated in this paper too. However the saving of some calculation time seems unjustified in consideration of the loss of information about the fracture angle and mode.

Keywords

strength criteria, fracture body, visualisation technique, inter fibre fracture, Coulomb,Mohr hypothesis, action plane, fracture angle, new testing technologies