Study On Bending Resistance Of Carbon Fiber Composite I-beam

This paper aims to investigate the effect of different size structure,different position layering Angle design and different fiber aggregate structure on the bending resistance of carbon fiber composite I-beam.The bending property of carbon fiber composite I-beam was tested by experiment.Secondly,the finite element method is used to model the three-point bending process of the composite laminated I-beam,and the validity of the model is verified.Then,the stress distribution and propagation law of composite laminated I-beam during bending are analyzed by using this model.The main research contents of this paper are as follows:1.The thickness and height of the upper and lower flange and web were changed respectively,and the composite I-beam was made and the three-point bending test was carried out.The finite element model of the three point bending process of the laminated I-beam is established and the stress distribution and propagation of the I-beam in the bending process are simulated and analyzed.The results show that the stress of the I-beam is mainly concentrated at the loading position of the I-beam and the supporting position of the base,and the load is transferred from the upper flange to the lower flange through the web.The stress on the upper flange is slightly greater than that on the lower flange,and the stress is transferred from the middle position to both sides of the flange.The stress value on the web increases all the time and transfers from the two ends of the web to the middle,and the stress value at both ends of the web is always greater than the middle of the web.Under the premise that the weight of the I-beam remains unchanged,the bending resistance of the I-beam can be improved by increasing the thickness of the upper flange appropriately,and the bending resistance of the I-beam can be slightly affected by increasing the thickness of the lower flange.Increasing the height of web properly can improve the bending resistance of I-beam,but increasing the thickness of web has a weak influence on the bending resistance of I-beam.2.The upper and lower flanges and web of I-beams were designed for mixed layup,and the upper flanges,lower flanges and web mixed layup I-beams were made,as well as all mixed layup and unidirectional all 0° layup I-beams,and the three-point bending test was carried out.The results show that the upper flanged mixed ply I-beam has the best bending resistance.The bending resistance of the I-beam with mixed ply is better than that of the unidirectional all-0 °I-beam.The bending resistance of the I-beam with mixed layup in one part is better than that of the I-beam with all mixed layup.The mixed ply structure can improve the matrix splitting in the fiber direction when the unidirectional ply structure is damaged.The mixed ply structure on the upper flange has better stability and can better transfer the load to the web and the lower flange.All mixed bedding has good stability,but the fiber decreases in 0° direction and the maximum bending load increases weakly.3.The bending resistance of 0°/90° mixed layup,twill fabric layup and three-dimensional woven composite I-beam was compared.The results show that the 0°/90° I-beam has the maximum bending load,followed by the twill fabric I-beam and the three-dimensional woven I-beam,and there is little difference in the maximum bending load between them.The 0°/90°layup and the I-beam with twill fabric layup solve the matrix splitting damage along the fiber direction of the unidirectional layup structure,but have obvious layered damage.The three dimensional woven composite I-beam not only improves the matrix splitting damage along the fiber direction,but also improves the stratification damage.