Hybrid Forming Of Aluminum Sheet /Plastics: Forming Process And Characterization Of Aluminum Sheet/Grafted Polypropylene Interface

In view of the dilemmas in fabrication and applications of sheet metal/thermoplastics combined macro-composite materials, a novel approach to manufacture this kind of metal/plastics combined macro-composite components has been proposed, in which forming of the sheet metal, injection molding of the plastic core and directly adhesion bonding between the formed sheet metal and the plastic core are integrated into one procedure. The elaborately designed experiments on a plastics injection molding machine with the cavity mold with a flat and a non-flat bottom respectively have been carried out, and the aluminum sheet/polypropylene combined components, having two aluminum sheet parts as the faces and a plastic core adhered to the inner surfaces of the aluminum sheet parts, have been prepared successfully.The forming process and the characteristics of plastic deformation, the sites of the heavily strained zones with severe thickness reduction and their evolution, the influences of the main processing parameters, such as the plastic melt pressure and its distribution from the gate to the end of the mold, and of friction coefficient between the sheet flange and the mold, on these during the hybrid forming of the aluminum sheet have been revealed by the updated Lagrange finite element formulation for the finite elastic-plastic deformation. The simulated results agree to the experiment.Influence of the cooling conditions, the amount of PP-g-MAH in copolymer of PP and PP-g-MAH, the temperature and the time of isothermal crystallization on microscopic morphologies and microscopic sizes of crystallization has been investigated. The processing conditions for fine spherulites have been determined.The crystalline structures of the copolymer of PP and PP-g-MAH on the adhered side solidified on aluminum sheet, which is the basis for studies of crystalline nucleation, growth and morphology of the plastics in the adhesion interface, have been analyzed by X-ray.The crystalline morphology of the copolymer of PP and PP-g-MAH in the interface of aluminum sheet/plastics and the influence of the main processing factors on it has been revealed. The nucleation mechanism of stress concentration in the grafted PP chains chemical interacted with pretreated surface of the aluminum sheet has been put out. This mechanism was used for explanation of the crystalline structures in the interface. A growth model of the transcrystalline in the interface of aluminum sheet/plastics has been proposed.The influence of the content of PP-g-MAH in the copolymer of PP and PP-g-MAH, the concentration of Y -APS, the temperature and the time of isothermal crystallization, on the single lap shear strength of adhesive bonding aluminum sheet/the plastics and on the curves of single lap shear load-displacement has been revealed, and the processing conditions for high adhesion strength were obtained.The failure surfaces of the single lap sheared specimens were studied by SEM, and based on this the model on deformation of the plastics, formation and evolution of the micro-voids as well as fracture damage of the adhesive bonding aluminum sheet/theplastics were analyzed.The X-ray photoelectron spectroscopy (XPS) spectrums of the interphases, on both adhesive sides of the aluminum sheet and the plastics, were detected by XPS apparatus. The features of the XPS spectrums were analyzed, and the failure loci of the adhesive bonded aluminum sheet/the plastics were determined. The distribution model of the molecule chains of PP-g-MAH and PP neighboring to pretreated surface of the aluminum sheet has been suggested. The interaction mechanism and the role of the PP-g-MAH and amino silane coupling agent, and furthermore the chemical adhesion mechanisms in the adhesive interface of aluminum sheet/the plastics, have been proposed as well.