The effects of aluminum nitride (AlN) and aluminum powder (Al) on thermal conductivity and electrical conductivity of silicone rubber compounds were investigated and it was found that the thermal conductivity increased with increased fillers content. Silicone rubber filled with Al powder of 45 μm over 50 phr, exhibits higher thermal conductivity as compared to that filled with AlN powder of 4 μm at the same filler content. The results indicate that the particle size effect played a significant role on thermal conductivity. In addition, it was found that electrical conductivity and thermal conductivity increased proportionally when the Al powder content increased. In contrast, only the thermal conductivity kept increasing proportionally, but the electrical conductivity almost remained unchanged for the rubber with AlN. Furthermore, a new type of silicone rubber compound with a combination of the two fillers, comprising 100 phr of AlN powder and 50 phr of Al powder, was developed, which lead to synergistic enhancement of the thermal conductivity. The improvement in thermal stability of the new type of silicone rubber compounds enables use in high temperature environments.
Four different surface treatments were performed on aluminum sheets that were then bonded with an epoxy-based film adhesive in an autoclave to achieve good adhesion. Specimens were examined to determine the microstructure of the porous oxide layer on the aluminum sheet surface and its effects on the bonding performance. Based on the failure modes of the bonded surfaces, the peeling strength, and an analysis of the microstructure of the porous oxide layer, this study showed that chromic anodizing the aluminum sheet had the best bonding performance, whereas sulfuric and hard anodizing exhibited the worst bonding performance. Hot etching exhibited a bonding performance somewhere between that of chromic anodizing and that of sulfuric anodizing. The chromic anodizing surface treatment can produce more pores on the oxide layer of aluminum sheet surface, which can enlarge the bonding areas and consequently enhance its bonding performance.
The study elucidated the relationship between the stacking sequence and physical properties, by investigating mechanical properties, fatigue life and the morphology, after fatigue fracture of carbon fiber/epoxy composites. The results show that the unidirectional carbon fiber laminate has the maximum tensile stress. Moreover, the laminate with ± 45 ° plies can improve the tensile strain. The fatigue life of all specimens was shorter than 10 3 cycles under high cyclic stress level, and longer than 10 6 cycles under low cyclic stress level. Laminates with [90 8 ] s stacking sequence had the shortest fatigue life under high and low cyclic stress, while the unidirectional carbon fiber laminate had the highest fatigue life. A number of fatigue damage models, including delaminating, matrix cracking and fiber failure, have been identified by scanning electron microscopy (SEM). The SEM micrographs showed that the morphology on the cross section, after fatigue fracture, was significantly correlated to the stacking sequence.
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