Fabrication Technology And Energy Absorption Mechanism Of Three-Dimensional Braided Composite Tube

Due to the characteristics of good integrity and strong design,the three-dimensional braided composite material overcomes the shortcomings of easy delamination and low damage tolerance in structure.The three-dimensional braided composite tube has continuous fiber bundles in the thickness direction,which has the advantages of resistance to delamination,high shear strength and good fracture toughness.It is used in the fields of automobiles,aircrafts,and transportation pipelines.In practice,tubes are inevitably subject to compression,which causes internal damage to the material and surface damage occasionally accompanied by energy absorption.In this paper,the effect of energy absorption under compression was studied in by taking three-dimensional braided composite tubes as the research object,and a quasi-static axial compression test was carried out.In order to explore the effect of braiding parameters on the axial compression properties of three-dimensional braided composite tubes,three sets of different braiding parameters(braiding angles of 30 °,45 °,60 °in 3 layers;braiding number of 3 layer,4 layer,5 layer with braiding angle of 30°,and with or without axial yarns in 3 layers with a braiding angle of 60°)three-dimensional braided composite tube samples were fabricated and carried out to an axial compression test,and the energy absorption mechanism of the composite tube under axial compression was analyzed.The research results of this article are as follows:For three-dimensional braided composite tubes,when the braiding angle is 30 °,as the number of braided layers increases,the maximum crushing stress of the composite tubes shows an increasing trend.When the number of braided layers is the 3 layers,with the increase of braided angle,the maximum crushing stress of the composite tubes decreases first and then increases.Additionally,the maximum crushing stress of the tube increases greatly after the shaft yarn is added to the threedimensional braided composite tubes,which shows that the shaft yarn has a significant effect on the maximum crushing stress of the tube.Different braided angles of composite tubes show different failure modes,there are three main failure modes after axial compression of the tubes,the first is the folding failure mode;the second is the flowering spraying which tube walls are bended failure mode;the third is hybrid both folding and bending failure mode.For carbon fiber composite tubes,different failure modes have a greater effect on energy absorption during axial compression.When the braided angles is 30 °,whether it is 3 layer,4 layer or 5 layer,not only do they exhibit similar folding and collaping phenomena,but also the specific energy absorption of composite tubes does not change much even their different crushing stress.When the number of braided layers is 3 layers,as the braided angle increases(30 ° to 60 °),the specific energy absorption of the tube decreases firstly and then increases again.Therefore,for the energy absorption characteristics of the three-dimensional braided composite tube,the effect of the braid angle has an impact on the failure mode and energy absorption effect,while the number of braided layers does not show an obvious effect.When the braided angles is 60 °,the specific energy absorption of composite tubes with shaft yarn has increased significantly which contributed to an improved energy absorption capability of the composite tube.Different failure modes of composite tubes have different energy absorption mechanisms.When the sample is in the folding failure mode,a large angle of deformation occurs on both sides of the sample during the compression process.During this process,a large number of fractures occur inside the carbon fiber bundle and this failure mode can absorb a lot of energy.And for the flowering spraying tube bending failure mode,a central crack will occur in the middle of the sample,there will be obvious branches on both sides of the tearing tube wall namely as fronds,and less fiber breakage,therefore less energy absorption.For the fold-bending hybrid failure mode,the tube folds downward in the form of a layer at the initial stage of axial compression.With the axial compression,the surface of the tube wall of the composite tube is obviously bent,and after the axial compression,the fiber bundles inside and outside the tube produce a lot of fractures,this failure mode absorbs a lot of energy.