Research On Impact Resistance Of Polyurea-Coated Foam Aluminum Composite Structure

As a shock-resistant buffer material,aluminum foam is widely used in transportation,aerospace,defense and military industries and other fields,and will inevitably suffer from dynamic shock loads.However,the unique pore structure of aluminum foam makes it prone to buckling failure when subjected to impact load,and the splash of fragments generated under high-speed impact load will cause certain secondary damage,and its protective performance needs to be further improved urgently.Polyurea as a structural surface coating has excellent protective properties,it is coated on the surface of closed-cell foam aluminum can help further improve its impact resistance,so this paper studies the mechanical response and energy absorption characteristics of polyurea-coated foam aluminum composite structure under impact load,the specific research work is as follows:（1）Using the semi-prepolymer synthesis method,the parameters of the stoichiometric ratio of polyurea,types and ratios of raw materials for polyurea semi-prepolymer components and amino-terminated polymer components,spraying machine spraying setting parameters were designed,the quasi-static and dynamic uniaxial tensile and compression tests were carried out on it.The results show that tensile and compressive stress-strain curve relationships of polyurea materials exhibit strain rate strengthening effect;the fracture failure modes under quasi-static and dynamic tension are ductile fracture and brittle fracture,respectively,during quasi-static and dynamic compression,polyurea deforms uniformly without cracks and it has strong superelasticity and large deformation capacity.（2）The dynamic compression test of aluminum foam by direct impact was carried out with a split Hopkinson pressure bar（SHPB）device,and the compression stress-strain curves of aluminum foam during the complete three-stage deformation process（linear elastic stage,platform stage and densification stage）were obtained;and with the help of electronic universal testing machine,the quasi static compression test of aluminum foam with low strain rate was carried out.Finally,the influence of relative density and loading strain rate on the compression performance of aluminum foam was analyzed,the results show that the mechanical properties of aluminum foam have significant relative density sensitivity,and the two are positively correlated;and with the increase of the loading strain rate,the yield strength and energy absorption capacity of aluminum foam are improved.（3）The stress-strain relationship curve of the polyurea-coated aluminum foam composite specimen under dynamic compression was obtained by using the dynamic impact test technique,and the influence of the strain rate on the performance of the polyurea-coated foam aluminum composite specimen was analyzed combined with quasi-static compression test data;combined with the performance change law of aluminum foam under static and dynamic compression,the effects of polyurea material and its coating position on the yield stress,plateau stress and energy dissipation per unit mass of aluminum foam were studied,the results show that polyurea improves the dynamic compressive bearing capacity and buffer energy absorption characteristics of aluminum foam,and the effect of coating polyurea on the back pressure surface is better.collect the specimens after the test,and analyze the failure mode before and after coating with polyurea aluminum foam combined with the deformation process of the specimen recorded by the ultra-high-speed digital camera,the results show that the polyurea coating reduces the damage of the foamed aluminum and effectively solves the secondary damage caused by the foamed aluminum structural fragments,which can guide the practical application of the project.