Research On Progressive Damage Analysis For Laminated Composites Containing Delamination

As a new material, fiber-reinforced composites have many merits,such as high strength-to-weight and high stiffness-to-weight properties,and it's mechanical performance can be designed for different pourposes.Nowadays it has been widely used in aerospace structures.It is well known that inter delaminations can drastically reduce the compressive strength of laminates.In order to improve the safety of usage,the damage theory of composites and the static residual strength of composites with initial damage must be studied.Several laminates with circler delamination and a real case of aero-engine with initial circler delamination have been investigated in this paper.The investigations in this paper will have important improvements for composites to be more widely used in aero-engines.In this paper a review of the research about the mechanisms of filure types and ultimate failure loads has been made.Additional attention has been emphasized on simulating methods for delamination growth in composite laminates.Based on ANSYS software,the research work of this paper is mainly including the following:(1) A three-dimensional progressive damage model has been developed for composite laminates containing embedded delamination subject to static loading.Contact conditions were applied to prevent physically inadmissible inter-penetration of the elements which located above and below the delamination area. A non-linear buckling analysis has been used to calculate the stress of laminates which will be used in subsequent progressive damage analysis.The model can be used to simulate the whole process of damage initiation,propagation and catastrophic failure of laminates,which is also capable of predicting the residual strength of structures.Five laminates containing embedded circular delamination were analysed,Good agreements were found between numerical predictions and experimental measurement results.(2) The trend of delamination along the edge of the initial delamination has been studied.The main factor which cause delamination to propagate was found for lamates containing different delaminations.A factor:delamination-factor was brought forth to weigh the trend along the edge of initial delamination.(3) The effect of delamination geometry on ultimate failure load,mechanisms of failure and bucking mode was also studied in this paper. (4) Finilly a real structure of aero-engine with initial embedded circular delamination has been studied.Four different FEM models were analized,each of them has different location of delamination.Different failure law,failure mode and ultimate failure load have been got.A conclusion can be drawn:when the diameter of the delamination is below 10mm, the structure of the aero-engine is safe.It is indicated that for specimens with delamination which located at the 1/4 distance between the top surface and the bottom surface of laminates have the largest trend to extend.