Experimental Study On The Damping Mechanism And Mechanical Properties Of High-Performance Aluminum Foam

As a new type of material, aluminum foam (AF) has been widely applied in recent years because of its excellent properties. Proceeding from the concept of "Material for Structural-Functional Integrated Application", a new kind of high-performance aluminum foam-Aluminum Foam/Polyurethane composite material (AF/PU) was manufactured in this thesis, using AF as the matrix material and filling the holes of AF with polyurethane (PU). This composite material was fabricated for the purpose of employing AF in the field of structural vibration control more widely. To understand the damping mechanism and mechanical properties of this new material, a series of experiments and numerical simulations were carried out, and the related conclusions are as follows:(1) The AF/PU composite material was tested under monotonic loads and cyclic loads. The influence of relative density of AF and the content of PU on the mechanical behavior of AF/PU was studied, and the deformation mechanism was obtained. Like pure AF, the monotonic compression curve of AF/PU is also composed of three stages, which are the elastic stage, the plastic platform stage and the densification stage. However, the deformation mechanism of this composite material deviates from pure AF due to the introduction of PU. AF/PU cell edges damage and collapse during loading owing to the incompressibility of PU. With strain increasing, the number of cracked cellular edges rises continuously until all edges fracture and the entire specimen fails. Also because of the incompressibility of PU, residual strain of this composite material reduces when loads are removed, and the elastic recovery performance improves correspondingly.(2) Damping tests were conducted on specimens that were compressed in advance for some cycles. The effects of relative density of AF, the content of PU, loading frequency and strain amplitude on the damping indicate that, the energy dissipation mechanism of this composite material is mainly attributed to the intrinsic damping of AF and PU, and the friction damping existing on the interface of these two materials.(3) The loading rate has little effect on the monotonic compression performance of AF/PU when the strain rate changes during the range of O.002s-1?0.05s-1. Within this range, the mechanical behavior of AF/PU could be well predicted using the phenomenological constitutive model proposed by Avalle. The constitutive model of broken line could better fit the hysteresis curves of this composite material if it has been compressed previously. This model captures the features of AF/PU during its whole deformation process under cyclic loads with parameters possessing distinct meaning, and is convenient to use.(4) The user material subroutine interface-Vumat, supplied by Abaqus, was used to add the macro-mechanical constitutive model of broken line into the finite element software. Test results of the constitutive model evidence that it concides with experimental curves. In addition, the model could reasonably depict the mechanical behavior of AF/PU under cyclic loads. Simulation results of AF/PU vibration performance demonstrate that it is feasible to make new damping equipment with this high-performance aluminum foam for vibration control, and the effect is noticeable.