THE EFFECT OF MULTIPLE DAMAGE IN COMPOSITE STRUCTURES - A THEORETICAL INVESTIGATION

This paper focuses on the problem of damage in composite structures and discusses the theoretical analysis of the effect of multiple damaged composite laminates subject to uniaxial and bi-axial loading. The interaction effect between two 27.5 mm diameter delaminations, with 9.5 mm diameter holes, was studied using a 3-D finite element analysis as a function of damage spacing. The compressive loads required for delamination growth were predicted using a Strain Energy Release Rate approach, viz. T*-integral. The results indicated that, for the particular layup analysed, the damage interaction can be considerable as the distance between the damage is reduced. The interaction effect appears to substantially increase T*, i.e. reduce the compressive load required for delamination growth, if the row of multiple damage is perpendicular to the applied load. T* also appears to increase, for all the cases considered, when bi-axial loading is applied.