Analysis Of Failure Mechanism And Local Buckling Capacity Analysis Of BFRP Foam Sandwich Wallboard Under In-Plane Axial Compression

Basalt fiber reinforced composites are known as "green high-tech materials" for their high strength,high elastic modulus,light weight,corrosion resistance,no pollution in the preparation process and so on.Basalt fiber sandwich panels are composed of basalt fiber reinforced composite materials and light core materials,which can be used as floor slab and wall panels in building structures,and can be used as bridge deck in bridge structures.In this paper,the failure mechanism of BFRP foam sandwich wall panel,which is composed of basalt fiber composite laminate and polyurethane foam,is studied by numerical simulation and theoretical model analysis under in-plane axial compression.On this basis,the calculation method for local buckling capacity of BFRP foam sandwich is proposed.The specific research work is as follows:(1)The relevant mechanical experiments of polyurethane foam,epoxy resin adhesive and basalt fiber were simulated respectively,and the reasonable constitutive models of these three materials were verified.Based on the three-dimensional Hashin failure criterion,the VUMAT subroutine suitable for basalt laminates was coded to meet the needs of failure discrimination and stiffness degradation of BFRP laminates in different directions.The accuracy of the constitutive model and subroutine was verified by the load-displacement curve.Based on this,a finite element simulation model of BFRP foam sandwich wallboard was designed,which simplified the modeling process.(2)The failure mechanism of BFRP foam sandwich wall panel under in-plane axial compression was analyzed.The simulation shows that the panel is unstable due to antisymmetric local buckling.Based on the damage evolution analysis of the benchmark model,it is found that the failure of BFRP foam sandwich wallboard is a progressive failure process and the result of a variety of damage coupling effects,among which the main effect is the axial compression damage,followed by the delamination damage.(3)Analyzed the influencing factors of the failure mechanism of BFRP foam sandwich wallboards,and designed three parameter change groups: length,number of webs and thickness of surface layer.It is found that the stability failure caused by local buckling is the main failure mode of sandwich wallboards.The length has an effect on the location of local instability.With the increase of length,the local buckling location tends to be concentrated.Both the number of webs and the thickness of the surface layer will affect the buckling instability mode of the plate.When the number of webs is small and the thickness of the surface layer is thin,the BFRP foam sandwich wallboards will have symmetrical local buckling,and the failure mode will be transformed into antisymmetric local buckling with the increase of the number of webs and the thickness of the surface layer.(4)Explored the variation law of local buckling capacity,the finite element simulation found that,in this paper,when the lengths of BFRP foam sandwich wallboards are increased,the stability of sandwich wallboard decreases.The length width ratio increased from 4.82 to24.09,and the local buckling capacity decreased by 17.6%.However,increasing the number of webs and the thickness of the surface layer will improve the stability of the sandwich wallboards.When the number of webs increases from 1 to 4,the volume content of BFRP increases from 10.19% to 13.47%,and the local buckling capacity increases by 25.57%;when the surface layers are increased from 2 to 5 layers,the volume content of BFRP increases from 8.20% to 14.32%,and the local buckling capacity increases by 44.15%.(5)In order to predict the local buckling capacity of BFRP foam sandwich wallboards more accurately under the load of in-plane axial compression,a formula for calculating the local buckling capacity of BFRP foam sandwich wallboards was deduced based on the principle of minimum potential energy.Equivalent elastic modulus and equivalent shear modulus were used to quantify the effect of web on local buckling capacity of sandwich wallboards,and coefficient L was introduced to modify the formula to quantify the effect of aspect ratio on stability of BFRP foam sandwich wallboards.The theoretical model deduced is in good agreement with the finite element results.