Analysis Of Buckling Properties Of Composite Stiffened Plates With Crack Defects

Composite laminate plates are widely used in aerospace and many other fields.The load capacity of the plate structure is largely determined by the buckling load.It is well known that structures still have a certain post-buckling load capacity after the first buckling load is reached.The state of buckling corresponds to an equilibrium configuration where a thin,flat plate bends under the coexistence of in-plane and out-of-plane loads.The composite structure may have different forms of cracks caused by the process of manufacture and assembly.Due to the installations of airborne equipment and pipelines,sometimes the aircraft components will open some holes.In this case,exploration of the buckling load for damaged structure with openings is particularly important.In this paper,the relation of the buckling load with respect to the crack length,crack angle,crack position and opening size of the cracked is investigated for non-stiffened and stiffened composite plates with cracks and structural openings.For the composite stiffened plate structure,the buckling analysis of the complete plate structure is performed,and the influence of factors such as the number of layers and ribs on the axial compression and shear buckling loads is investigated.The post-buckling path is achieved through the finite element software and its subroutine interface.And progressive damage analysis is carried out numerically.It is shown in the present study that the change of the length of the crack will generally have a negative effect on the low-order buckling value,but it may fluctuate for the high-order buckling load;the change of the crack angle and the distance between multiple cracks will produce more complex buckling loads,and the low-order buckling load tends to show a wave-like change.The trend of the buckling load of the plate with open holes and cracks in the surface are related to the size of the opening and the position of the crack,and sometimes the buckling loads may increase due to the increase of the crack length.The increase in the number of ribs and the number of ribs will lead to the increase of the buckling load.The damage to the panel and ribs in the post-flexion state will occur more in the matrix part of the material.