Research On Bearing Capacity Of BFRP Composite L-joints Under Bending Load

The building components made of basalt fiber reinforced polymer(BFRP)are combined into prefabricated buildings,which have the excellent characteristics of light weight,high strength and small electromagnetic shielding effect.L-joint is a typical joint form in prefabricated buildings.It is often used to connect roof and wall,wall and wall.At present,there are very few studies on sandwich composite L-joints at home and abroad.In this paper,the mechanical performance of L-joint between roof and wall under bending load is studied.The main research contents and results are as follows:(1)The finite element method was used to study the performance of L-joints of GFRP sandwich composites under bending load in existing tests.In the analysis,Sokirieh-Hashin failure criterion and reasonable stiffness degradation model suitable for braided fibers were selected.The ultimate strength and failure mode of the joints obtained are in good agreement with the experimental results.The accuracy of the finite element method is verified.(2)Four types of BFRP L-joints are proposed,numbered as LA,LB,LC and LD,and the failure load and failure mode of the joint under bending load are analyzed.The 4 L-joints can be arranged as LA,LB,LD and LC according to the order of ultimate load value from large to small.In terms of failure modes,LA and LD are: 1 direction Fiber fracture failure,fiber matrix shear failure and panel delamination failure;LB and LC nodes are: panel delamination failure.(3)Taking the LA joint with the largest ultimate load value as the research object,the effects of the thickness of connectors,the lap length of connectors,the thickness of roof and wall and the thickness of foam on the bending capacity and failure mode of the joint are analyzed.The results show that the thickness of roof and wall has the greatest influence on the ultimate load of the joint,followed by the thickness of foam and connectors,The lap length of the connector has the least influence.As for the final failure mode of La joint,the four factors have no effect on the location of various failures of the panel when the joint is finally damaged,which are all in the inner and outer corners of the connector;The foam of all models did not fail,and there was no debonding failure.(4)In order to make the failure occur on the plate rather than the connector as much as possible,the influence of four factors on the failure of the two components was studied:changing the lap length of the connector could not make the failure of the connector less than the failure of the plate;On the premise of ensuring the bearing capacity of joints,when the thickness of connectors is 2 times of the thickness of panels and the thickness of foam is 20 times of the thickness of panels,the failure of connectors can be effectively controlled to be less than that of panels.