| Fiber reinforced metal laminates(FMLs), represented by Aluminum alloy- glass fiber / epoxy(Glare), show excellent mechanical properties, especially its outstanding fracture, impact and fatigue resistance. Due to these distinguishing features, FMLs have been widely applied in various field, such as aerospace and automotive filed. Compared with aluminum alloy, magnesium alloy is more lighter, with good specific stiffness, specific strength, damping and electromagnetic shielding performances. With the research and development of Glare laminate for reference, it is possible to develop a new type of laminate by replacing aluminum alloy with magnesium alloy. If so, it is feasible to produce a new lightweight laminate. Meanwhile, it is also possible to find a new method to improve the anti-corrosion performance of magnesium alloy. In this work, the surface treatment of magnesium alloy sheet was first studied. Then, a new Glass fiber reinforced resin / Magnesium alloy / Glass fiber reinforced resin laminate was prepared. At last, the mechanical properties and anti-corrosion performance were investigated. The main work and conclusions are as follows:(1) Through sanding by sandpaper, the magnesium alloy sheet with different surface roughness were prepared. Then, the surface morphology of magnesium alloy was observed by optical microscope, and tensile shear properties of magnesium alloy / glass fiber reinforced resin composite laminate was tested and analyzed. Results show that the tensile shear strength by # 120 sandpaper magnesium alloy sheet of the composite plate is 8.6MPa, higher than 6.0MPa of 1000# and 4.3Mpa of 2000#. For the composite laminate prepared by magnesium alloy sheet that sanded by 120# sandpaper, the tension shear elastic was 0.5GPa, slightly higher than that treated by 1000# and 2000# sandpapers, while there was few variations. Through the observation of SEM images of tensile shear fracture, it was found that the fracture of composite laminate prepared by magnesium alloy sheet treated by 120# sandpaper was inclined to the cohesive fracture of resin layer. However, the composite laminates prepared by magnesium alloy sheet treated by 1000# and 2000# sandpaper were inclined to the attached fracture. Namely, the magnesium alloy sheet with relatively coarse is helpful to the improvement of bonding strength of the composite interface.(2) In this work, the thermoforming process was studied and optimized for the preparation of glass fiber reinforced plastic / magnesium alloy composite laminates. Results showed that the best parameters were as follows: temperature of mould 140?, Pressure of hot press 6MPa and temperature of heat preservation for 30 min. With this process, the composite laminate was prepared by magnesium alloy sheet treated by 120# sandpaper. Its mechanical properties were as follows: tensile strength 298.9MPa, tensile modulus 32.6GPa, elongation 3.0%, flexural strength 243.2MPa, bending modulus of 22.6GPa. These values were all 8%- 13% higher than that of composite laminates prepared by 1000# and 2000# sandpaper. Besides, the tensile strength of the composite plate is 10.4% higher than that of magnesium alloy.(3) With the methods of SEM observation, weight loss and mechanical performance testing, the corrosion resistance of the composite laminates after immersion in saline solution at different temperatures, concentrations and pH values were investigated in the work. The results were as follows:1) Temperature of saline solution had an obvious influence on the corrosion resistance of laminate: under high temperature, the corroded surface of composite laminate was larger than that under room temperature; besides, the weight of composite laminate specimen after 7d of immersion in saline solution decreased by 0.19%, and the tensile strength decreased by 7.8%. However, for the specimen immersed into saline solution under room temperature, the corroded surface of magnesium alloy and weight showed little variations, and the tensile strength of specimen only decreased by 2.7%. Namely, such composite laminate showed good corrosion resistance in the saline solution under room temperature.2) solubility of saline solution had an little influence on the corrosion resistance of composite laminate: when the specimen of composite laminates have been corroded in the saline solution with concentration of 1.5 wt.% And 5.0wt.%, the weight of specimen and corroded surfaced of magnesium alloy sheet showed little difference compared to that of original magnesium alloy sheet. Furthermore, after immersed into saline solution with concentration of 1.5 wt.% and 5.0wt.% for a week, the tensile strength was decreased by 4.7% and 5%, respectively.3) The pH values of saline solution showed obvious influence on the corrosion resistance of laminate: after immersed into the saline solution with the pH value of 3.5, the weight of specimen was decreased by 0.19%, and the tensile strength and bending strength decreased by 8.7% and 16.8%. While after 7d of immersion into saline solution with pH value of 10.5, the weight of specimen only decreased by 0.08%, and the tensile strength and bending strength decreased by 2.0% and 7.6%.4) In a word, the composite laminates show significantly superior corrosion resistance compared to magnesium alloys, even under harsh environments, such as high-temperature and acidic solution. However, for the original magnesium alloy sheet, it will be totally corroded after a few hours in saline solution under room temperature. |
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