THE EFFECT OF MULTIPLE DAMAGE IN COMPOSITE STRUCTURES - A THEORETICALINVESTIGATION

This paper focuses on the problem of damage in composite structures an d discusses the theoretical analysis of the effect of multiple damaged composite laminates subject to uniaxial and bi-axial loading. The int eraction effect between two 27.5 mm diameter delaminations, with 9.5 m m diameter holes, was studied using a 3-D finite element analysis as a function of damage spacing. The compressive loads required for delami nation growth were predicted using a Strain Energy Release Rate approa ch, viz. T-integral. The results indicated that, for the particular l ayup analysed, the damage interaction can be considerable as the dista nce between the damage is reduced. The interaction effect appears to s ubstantially increase T, i.e. reduce the compressive load required fo r delamination growth, if the row of multiple damage is perpendicular to the applied load. T also appears to increase, for all the cases co nsidered, when bi-axial loading is applied.