| A new kind of 3D angle-interlock woven composites material is developed,which is a whole structure connected by multi-layer warp and weft yarns.Different from the traditional laminated composite,3D angle-interlock woven composites introduces reinforced fiber in its thickness direction,which greatly enhances the anti delamination performance of composite under impact load.With its ultra-high tensile,bending and compression strength,high impact toughness,fatigue strength,damage tolerance and energy absorption rate,it can be widely used in aerospace,military defense,explosive processing and public security fields.In this paper,the basic mechanical properties and low-speed impact mechanical properties of 3D angle interlock woven composites are studied by means of experiment and numerical simulation.The main research work and innovation achievements include the following aspects:(1)The static tensile test of UHWMPE fiber bundle was carried out to explore the remaining tensile strength and tensile film amount of UHWMPE fiber bundle after spinning.The strength retention and modulus retention of UHWMPE fiber bundle after spinning are 0.4-0.6 and 0.3-0.5 respectively.The tensile strength and modulus of the fiber bundle decrease obviously in the spinning process.(2)The quasi-static tensile and compression properties of 3D angle-interlock woven composites were studied.The 3D angle-interlock woven composites is used as reinforcement and polyurethane resin matrix material for curing and forming,and then it is cut into a test piece conforming to the relevant test standards after being made into a plate detail.According to the quasi-static tensile tests in warp,weft and 45~o directions,the tensile properties of 3D angle-interlock woven composites under quasi-static conditions were obtained.The tensile strength and modulus of the composites are about 96.84MPa and 2.19GPa respectively in the longitudinal tensile test.In the latitudinal tensile test,the composites only show fiber pull-out failure,and the tensile strength and modulus are ignored.The yield point of the specimens in the 45~o direction appears when the stress is 9MPa,and the fracture of the composites appears near the stress of 7-9MPa.The reason why the tensile strength and modulus of the three directions of the 3D angle-interlock woven composites are low is that the content of polyurethane matrix material is small and the strength is low.In the composites,polyurethane material only plays the role of maintaining the spatial structure of the 3D angle-interlock woven composites,and its contribution to the strength and modulus of the composite is small.The static compression tests of different layers were carried out to explore the influence of layers on the compression properties of composite materials.The compression modulus of single layer of 3D angle-interlock woven composites can reach 965.79MPa,and the compression failure strength is 221.55MPa;the compression modulus of double layer composite can reach909.18MPa,and the compression failure strength is 197.76MPa;the compression modulus of three layer composite can reach 758.61MPa,and the compression failure strength is 132.35MPa;the compression failure strength of four layer composite is 89.82MPa,and the modulus under compression test is 589.88MPa.With the increase of the number of layers,the compressive strength and modulus of the composite are gradually reduced.(3)The response characteristics of 3D angle-interlock woven fiber composites under low-speed impact were investigated.The impact resistance of 3D angle-interlock woven composites under low-speed impact was tested by Instron ceast 9350 drop weight impact test system.The impact velocity of drop hammer is 3m/s,4m/s,5m/s,6m/s and 7m/s respectively.The energy absorbed by the target material increases from 18.64J to 430.49J,and the energy absorption rate increases from 17.25%to 69.83%.The energy absorption form of the 3D angle-interlock woven composites is the large deformation in the direction of impact,which is not conducive to its protective effect.(4)The geometric model of 3D angle-interlock woven composites was established by texgen fabric modeling software,and the tensile modulus of 3D angle-interlock woven composites was calculated by ABAQUS finite element software,and the effect of fabric layers on the modulus of elasticity was studied.The tensile modulus of the composite is 1.703GPa,2.005GPa,2.249GPa,2.284GPa and 2.517GPa,respectively.With the increase of fabric layers,the longitudinal tensile modulus of the 3D angle-interlock woven composites increases linearly,but when the number of layers reaches six,the upward trend slows down,and the contribution of fabric layers to the tensile modulus of the 3D angle-interlock woven composites decreases gradually.(5)Using ANSYS/LS-DYNA finite element software,a numerical simulation model of low-speed impact is established to simulate the process of low-speed impact of drop hammer.The contact force time curve of impact head is compared with the test results,and the influence of drop hammer impact speed and 3D angle-interlock woven composites target plate thickness on drop hammer contact force and target plate failure morphology is explored.With the increase of the impact speed,the maximum contact force of the impact head increases gradually,and the time to reach the maximum contact force of the drop hammer advances gradually.The impact process is divided into two stages:in the first stage,the contact force increases with time,the UHWMPE fiber and polyurethane matrix material at the front of impact are subject to compression shear,the fiber and matrix material at the back of impact are subject to tensile shear,and the two failure modes make the composite quickly absorb the kinetic energy of impact head.The second stage is the large deformation stage.When the contact force of the impact head reaches the maximum,the relative slip between the composite target plate and the fixture causes the resultant force of the drop hammer impact head to decrease rapidly to zero. |
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