Research On The Trigger Structure Design And Multi-coupled Triggering Mechanisms Of Composite Corrugated Plate

Composite structures have been widely used in aerospace and vehicle engineering structures due to the advantages of high specific strength,high specific stiffness and strong designability etc.Composite structure absorbs a large amount of energy through various complex failure modes under impact loading.The energy absorption characteristics of composite structures are susceptible to various factors,and the trigger mechanism is a key factor affecting the energy absorption characteristics of composite structures.A reasonable triggering mechanism enables the composite structure to stabilize the progressive damage in a controlled manner and fully dissipate the energy.With the improvement of the per formance requirements of energy-absorbing structures in engineering applications,a single trigger mechanism can no longer meet the engineering needs.Therefore,the trigger structure design of composite corrugated plate is studied in this work,and the influence of multiple coupling trigger mechanism on energy absorption characteristics is studied.A numerical model is established based on continuum damage mechanics,which can accurately simulate the quasi-static axial crushing load of composite corrugated plate.The damage model is consisted of the nonlinear constitutive relation of fiber,matrix and interface,failure criterion and a stiffness degradation theory,so as to study the damage evolution process of material properties.The main research works are summarized as follows:Firstly,a numerical damage model including an intra-layer damage model and an inter-layer damage model is established.Taking the composite corrugated plate as the research object,several failure criteria for determining the initial failure in the intra-layer damage model include the maximum stress failure criterion,the Hashin failure criterion,the hybrid failure criterion based on Hashin and Yamada-Sun failure criterion(H-Y failure criterion),and the stress-based Linde failure criterion.The analysis of some typical parameters affecting the failure criterion and the damage evolution process reveals the initial criterion for the failure of the layer which is most suitable for the composite corrugated plate numerical model.The optimal initial inter-lay failure criterion for composite corrugated plate of numerical model is presented.In addition,some typical parameters affecting the failure criterion and the damage evolution process are analyzed.Then,a novel plug-type initiator is proposed to improve the energy absorption characteristics of composite corrugated plate.To make the material fully destroyed in the crushing process,the novel plug-type initiator restricts the space of corrugated plate by a corrugated-shape geometry cavity.The finite element model of composite corrugated plate crushing failure is established,and the influence of typical parameters including the ditch width and the inner geometry is studied.The results show that the use of a corrugated-shape ditch plug initiator can improve the energy absorption capacity of the corrugated plate crushing failure.Energy absorption(EA)and specific energy absorption(SEA)are inversely proportional to the ditch width,and the change in the inner geometry not only improves the energy absorption capacity but also reduces the initial peak load.Finally,based on the progressive energy absorption concept,a multi-stage composite corrugated plate is proposed,and its progressive failure behavior and multiple coupling triggering mechanism are studied.Multi-stage composite corrugated plate are realized by multi-layer corrugated plate gradient stacking,which induces progressive load-displacement response and failure modes.The effects of typical parameters such as the number of layers of each gradient stack,the height between adjacent gradient plate,and the stacking order of gradients on the energy absorption characteristics of multi-stage composite corrugated plate are discussed.Finally,the multi-stage trigger type is introduced for multi-stage composite plate,and the influence of different trigger forms on the energy absorption characteristics are analyzed and compared.