Failure And Energy Absorption Of Composite Thin-walled C-channels Under Axial Compression

Since composite materials have high specific strength and rigidity,as well as great design potential,they are widely used in civil aircraft.Due to the brittle property of composite materials,their failure mode under compression is complex,which is directly related to the fracture mechanism,and ultimately,affects the energy absorption capability of the structure.In addition,the stability of the thin-walled structure under axial compression load determines whether the thin-walled structure can continue to bear.It is important to control the failure mode to achieve great energy absorption through structural design of the composite thin-walled C-Channels.Besides,it is essential to establish a finite element model that can represent the failure behavior and energy absorption characteristics of C-Channels.The work contents are as follows:Firstly,the composite thin-walled C-Channel was designed.The bolt connection was designed through static analysis.The ply lay-up and basic configuration of the C-Channels were considered.Flange transition and ply drop-off design were introduced.Secondly,axial compression test was performed.The effect of ply lay-up,flange width,flange transition and ply drop-off on the failure mode of the structure were analyzed.The energy absorption capability was assessed by studying the average compression load,energy absorption and specific energy absorption.Its failure is a complex process that couples local buckling deformation and brittle fracture.The ply lay-up affects the failure mode and energy absorption capability of the C-Channel,the flange width mainly affects the stability of the structure,the flange transition and ply drop-off designed specimen can withstand high compression load in the late compression process,which can be used to achieve gradual energy absorption.Finally,finite element analysis of the composite thin-walled C-Channel was performed.Firstly,eigenvalue analysis was performed to study its compression stability and buckling mode.Then,the interlaminar and interlaminar model were studied,the stacked-shell model was established.The deformation and failure modes of the structure during compression were studied.In terms of local failure morphology,the model can well capture the failure process at chamfers and ply drop-off zone as well as the delamination.In terms of overall failure morphology,it can well simulate the tilt and lateral fracture as well as material stack of the specimen.The load-displacement curve and the energy absorption characteristics parameters in the test and simulation match well.The model is effective and reliable.