Progressive Delamination Growth In Composite Laminates With Fasteners Under Fatigue Load

Composite laminates have been widely used in modern aircraft industry because of their perfect mechanical properties.However,the manufacturing defects and impact damage defects arise in the composite structure during the process of production and use,which will lead to a decline in the bearing capacity and service life of the structure,and even threaten the safety of the aircraft seriously.The delamination damage is the most important form of damage in composite laminates,which is often repaired by using fasteners in engineering.The effect of fasteners on delamination growth is studied.A developed finite element model combining virtual crack closure technology(VCCT)with VUMAT subroutine was established to study the inhibition mechanisms of fasteners on the delamination growth of composite laminates with buried delamination based on ABAQUS software.The VCCT was used to calculate the energy release rate,then the delamination growth was simulated by B-K criterion.Based on that,the static delamination growth characteristics of laminates with buried delamination are simulated,and the inhibition mechanisms of fasteners on the delamination growth is studied,too.A parametric study on the effects of delamination and fastener size,delamination position,layer order and other parameters was further performed.Based on ABAQUS/Explicit software,the residual strength model and the improved Hashin criterion in VUMAT subroutine were used to weaken the properties of materials and judge the failure of element respectively.the fatigue delamination growth characteristics and the inhibition mechanisms of fasteners on the delamination growth are studied.At the same time,the influence rule of the parameters on fatigue delamination propagation is studied.The conclusion is of practical significance to the design of repair method.