Discrete Element Simulation And Experimental Study On The Tensile Propertyof Glass Fibre Reinforced Composite Plate

Fiber reinforced composite material is a new type of high-performance materials which is made up of fiber and matrix according to the specific way.Since high specific strength?corrosion resistance and designable,fiber reinforced composite material has been widely used in the aircraft industry,such as Boeing series.With the rapid development of civil engineering industry,the performance of engineering materials in modern architecture is higher and higher.Fiber reinforced composite materials are also widely used in structural engineering,mainly in the form of the laminate,such as fiber processing engineering structure?large span transmission tower?the corrosion resistance of offshore platform.The damage mechanism and calculation method under the complex stress is the basic application of fiber reinforced composite material.Currently the conventional finite element method based on continuum mechanics is difficult to capture the slip?fracture and fragmentationbetween different material particles in micro scale and its effect on the overall destruction,also unable to explain how the damage of composite materials under complex stress produce and how to development and evolution.In order to avoid the limitations of the traditional methods,the paper use discrete element method which is based on non-continuum mechanics theory,combined with theory and experiment analysis,taking glass fiber reinforced composite plate(GFRP)as the object of study,presented method of discrete element modeling of composite materials and components and microstructure parameters of fiber reinforced.Specific work includes the following aspects:1.Based on orthogonal anisotropic elastic theory and discrete element theory,the paper presented a 19-spheres 3D discrete element model under strain potential energy densityreciprocal method,also inferred a theoretical formulas for the transformation between the discrete microscopic stiffness parameters and the material macroscopic elastic parameters.Finally,it respectively concluded the 6 contacts model for the Poisson's ratio less than 0.25 and 4 contacts model for the Poisson's ratio less than 0.33.It provides a theoretical method for the discrete element modeling of fiber reinforced composites and the determination of the stiffness microscopic parameters.2.The GFRP plate?GFRP plate with hole and bolt node GFRP bolt joint tensile tests were carried out.During the tensile tests,non contact video gague method for fiber reinforced composite material is analyzed.The whole process from the initial stress to the final failure of the GFRP plate,the GFRP plate with hole and the GFRP bolt joint is obtained,which provides experimental datas for study on failure mechanism of test specimens and the determination of the discrete element microscopic parameters.3.By using the above mentioned microscopic parameter calculating method,GFRP plate?GFRP plate and GFRP bolt joint tensile tests are simulated by discrete element method.And it is proved that the method of microscopic parameter calculating in the elastic stage is correct.According to three kinds of tensile test,8 strength values of the 19 ball model(4 kinds of contact pairs)are calibrated.The specific calibration process is as follows:first of all,the normal strength of three kinds of contact in the tensile plane is calibrated by simulating the tensile test of GFRP plate;then,the shear strength of three kinds of contact in the tensile plane is calibrated by simulating the tensile test of GFRP plate;finally,the GFRP bolt joint tension test is carried out to verify the correct value of the three contact strength values in the tensile plane,and to calibrate the strength value of the thickness direction.Through the above research,it put forward a kind of 3D discrete element modeling for orthotropic materials and the stiffness of the micro parameters calculating method,and presents a set of calibration procedure for contact strength of discrete element based on typical fiber reinforced composite tensile failure test.This work provides a numerical method for the study of the failure behavior of fiber reinforced composites under complex stresses,which has important theoretical significance and practical value.