Airframe construction in conical form is the most desired shape of flight hardware due to their low drag profile and are located at the fore-end region of flight vehicles encountering high drag loads. Owing to their tailoring capability, materials with orthotropic mechanical properties are preferred choice. Presence of delamination causes reduction in strength and stiffness of laminated composite structure and detrimental to the safety and stability of structures made of composite materials. Determination of the residual strength and stiffness with respect to a finite size of delamination would be helpful in assessment of structures fitness to usage whenever the defects are identified by non-destructive procedures. Experimental study is carried out with building block approach i.e. on specimen, laminate and component.
In specimen level, fracture testes (mode I & mode II), have been carried out for uni-directional plies and multi-directional plies representing edge delamination situation.
Experiments of in-plane compression testing of multidirectional laminate with an embedded delamination at the centre are carried out. For the purpose of reference, tests of an ideal laminate with identical ply sequence and without delamination are carried out.
Stability studies under embedded delamination in orthotropic cone shaped shells under axial load and external pressure load is performed. The effect of delamination size and it’s through the thickness position on the mechanical performance of the cone shaped shell is investigated. The investigation is performed for metal and composite materials with 3 types of stacking sequences generally used in practical designs. The normalized buckling factor is showed graphically with the normalized defect size.
Tests of composite conical shell under axial compression (ideal & with embedded delamination) are performed Delamination is placed at multiple depths without influencing each other and minimal effect of loading and constraint condition. Strains and displacement are monitored until failure.