Study On Mechanical Properties Of Three-dimensional Needle-punched Composites

In recent years,the research and application of composite materials have been flourishing all over the world.Three-dimensional needle-puncjhed composites are a new type of composites.The needle-punched fibers are introduced into multi-layer two-dimensional fibre fabrics to form three-dimensional prefabri cated structures so as to enhance the properties in thickness direction.This kind of composites not only has excellent mechanical properties,but also overcomes the complexity of the manufacturing process of the composites.It can be widely used in aerospace and other industrial and military fields.It also has broad application prospects in civil aviation industry,marine industry,civil infrastructure and land transportation industry.However,the current research on three-dimensional needle-punched composites has great limitations,which limits its application.In view of its practical application environment,the preparation and mechanical properties of three-dimensional needle-punched composites were studied.Specific accomplishments and achievements are as follows:(1)Three-dimensional preforms with dilferent volume fractions of fibers were obtained by needling process.Three-dimensional needle-punched composites reinforced with carbon fibers,basalt fibers and quartz fibers were successfully prepared by vacuum assisted resin transfer molding process.(2)Bending tests were carried out for the prepared materials,and the high temperature bending properties and failure mechanism of the materials were studied and analyzed.The results show that the bending properties of the composites decrease with the increase of temp erature;the increase of fiber volume fraction can improve the bending properties of the composites;and the bending properties of carbon fiber reinforced composites are better than those of the other two kinds of fiber reinforced composites.(3)The failure mechanism of the composites was analyzed from both in-plane and out-of-plane directions through high temperature compression experiments at six temperature points.The results show that temperature has a significant effect on the compressive properties of materials;the compressive properties increase with the increase of fiber volume fraction,the compressive strength of materials in the out-of-plane direction is higher,but the compressive modulus is lower than that in-plane direction;the different types of reinforcing fibers also have a great influence on the compressive properties of materials.(4)The strain rate effect of materials is studied and analyzed by Hopkinson compression bar test.The results show that the prepared needle-punched composites are sensitive to strain rate,and the peak stress increases with the increase of strain ra.te;the impact strength at high strain rate increases with the increase of fiber volume fraction;the impact resistance of basalt fiber reinforced composites is greater than that of carbon fiber reinforced composites;The damage mode of carbon fiber material is brittle,and that of basalt material is debonding.