Study On Impact Compression Mechanical Properties Of PP/CF Reinforced Coral Sand Cement-based Composites

Polypropylene fiber tensile strain hardening and good elongation,carbon fiber corrosion resistance and high strength.Carbon fiber and polypropylene fiber were mixed into coral sand cement-based composites prepared by artificial seawater,and four kinds of reinforced coral sand cement-based composites of hybrid carbon fiber and polypropylene fiber with different fiber content were obtained.The static compression tests of reinforced coral sand cement-based composites of hybrid carbon fiber and polypropylene fiber with test block age of 7 day and 28 day were carried out by using SYE-2000 pressure testing machine.The impact compression tests of reinforced coral sand cement-based composites of hybrid carbon fiber and polypropylene fiber under five strain rates were carried out using a split Hopkinson pressure bar with a diameter of 100 mm.The test strain rate was 50-240 s^-1.Based on the test data,the Holmquist-Johnson-Cook constitutive model was debugged to make it suitable for reinforced coral sand cement-based composites of hybrid carbon fiber and polypropylene fiber.Based on the Holmquist-Johnson-Cook constitutive model after debugging,simulation of impact compression test process of NO.4 proportioning materials by LS-DYNA The impact compression mechanical properties of reinforced coral sand cement-based composites of hybrid carbon fiber and polypropylene fiber were studied by analyzing the failure mode of the test block,stress and strain curves,strain rate effect and energy dissipation.The main research results of this paper are as follows:（1）With the hybrid content of carbon fiber and polypropylene fiber increasing,the static compressive strength of reinforced coral sand cement-based composites of hybrid carbon fiber and polypropylene fiber shows a trend of first decreasing and then increasing.After adding 15.75 kg/m³carbon fiber and 1.82 kg/m³polypropylene fiber into coral sand cement-based composites,the static compressive strength of the test block increased by 26.57%at age 7 day and 18.78%at age 28 day.（2）The use of coral sand fine aggregate leads to many defects such as micro cracks and micro voids in the test block.The improvement of hybrid fiber on the impact compressive strength of coral sand cement-based composites is limited,but the impact toughness of coral sand cement-based composites is significantly improved.（3）Under the same impact load,the damage degree of hybrid carbon fiber and polypropylene fiber is relatively lighter than that of undoped fiber.The critical strain rate of reinforced coral sand cement-based composites of hybrid carbon fiber and polypropylene fiber is 200 s^-1.When the strain rate is greater than 200 s^-1,the fiber network formed by hybrid carbon fiber and polypropylene fiber strengthens the toughening effect of the test block.（4）The peak stress of reinforced coral sand cement-based composites of hybrid carbon fiber and polypropylene fiber has obvious strain rate effect,and the dynamic increase factor of the material is highly sensitive to the strain rate.（5）Based on the Holmquist-Johnson-Cook model after parameter debugging,LS-DYNA was used to numerically simulate the impact compression test process of hybrid carbon fiber 15.75 kg/m³and polypropylene fiber 1.82 kg/m³test blocks.The error between the numerical simulation results of the peak stress of the test block and the test results was concentrated in 0.67-5.97%.The failure mode of test block agrees well with the simulated failure mode,and the reliability of the numerical simulation results was high.