Extended Layerwise / Solid-Element Method Of Composites Structure

Composite stiffened plate and sandwich structures have been widely used in the main bearing structure of the aircraft at present.Study on the mechanical behavior of damaged composite structures has significance for damage tolerance analysis and structural airworthiness of composite structures.The extended layerwise/solid-element(XLW/SE)method is established based on the extended layerwise method(XLWM)and 3D solid elements,analyzing the problems of damage of the stiffened composite plate and sandwich structures(the lattice sandwich structure and the honeycomb sandwich structure).XLW/SE has advantages of simple modeling and analyzing complex structures.It can simulate transverse matrix cracks and delaminations,and analyze static response problems between stiffeners or cores and plates.XLW/SE of the stiffened composite plate is established.In this method,the governing equations of composite plates and stiffeners are established based on XLWM and 3D solid elements,respectively.The final governing equation of stiffened composite plates is assembled by using the compatibility conditions and internal force equilibrium conditions at the joint interface between the plates and stiffeners.The stiffened plates without damage and with damages including delaminations or/and transverse matrix cracks are considered.The results obtained by the present method are in good agreements with those of 3D elastic model.The stress intensity factor of the crack tips is calculated when the stiffened plate exists transverse cracks.At the same time,the influences of the location of transverse matrix cracks and delaminations to the stress intensity factor and maximum displacements are studied,respectively.XLW/SE of the sandwich structure is established based on XLWM and 3D solid elements,respectively.In this method,the governing equations of top and bottom composite plates and cores are established based on XLWM and 3D solid elements,respectively.The final governing equation of sandwich structure is assembled by using the compatibility conditions and internal force equilibrium conditions at the joint interface between top and bottom plates and cores.The sandwich structures without damage and with damages including delaminations or/and transverse matrix cracks are considered.The results obtained by the present method are in goodagreements with those of 3D elastic model.