Cr2O3 nano-powders were successfully fabricated with using chromium nitrate and
aqueous ammonia as starting material and urea as dispersant agent by sol-gel method. The
formation of crystalline phase during heat treatment of dry gel was characterized by differential
thermogravimetry (DTG) and X-ray diffraction (XRD) techniques and the temperature of
calcination was determined as 400°C. Scanning electron microscopy (SEM) was utilized to observe
the morphology of the as-fabricated Cr2O3 particles. The results showed that Cr2O3 particles are
spherical or square with little agglomeration and a diameter of about 30 nm. The specific surface
area of Cr2O3 particles was measured as 44.23 m2/g by Brunauer-Emmett-Teller (BET).
In this paper, adherend thickness influence on the bond strength was evaluated by single-lap shear testing. The adherend for joining was carbon/epoxy composites with four different thickness made of fabric prepregs. The adhesive system for joining included two types of adhesive film, namely J-135 and J-95. The results showed that adherend thickness have a significant influence on the bond strength. In the range of adherend thicness from 2.26 mm to 4.52 mm, the bond strength demonstrated a wavy change with increasing adherend thickness. Through comparison of the bond strength of joints with two adhesives at room temperature and aging condition, adhesive J-95 was proved to have better resistance to elevated temperature and humidity than J-135.
The response of adhesively bonded lap-joint under transverse impact was investigated by means of DYTRAN software. A finite element model was developed based on cohesive failure in the adhesive layer of the joint. It was found that transverse impact results in shear and peel stress concentration in the adhesive due to the considerable deflection of the joint. The stress distribution in the adhesive layer was asymmetric along the overlap length direction. The peel stress varies from tensile to compressive from one side to the other. Two cracks initiated at two sides of the adhesive layer were observed before the failure of the joint.
An experimental study of co-injection molding which involves sequential injection of dissimilar metal feedstocks into a mold has been carried out. The effect of skin temperature and injection velocity on the material distribution of co-injection molded plates has been studied. It was found that the molding temperature was important in controlling skin-core distribution, while injection velocity seemed to play no significant role. The experimental results were analyzed by taking account of the relative viscosity of the two melts. It was demonstrated that the differences in rheological properties of the metal feedstocks involved are the primary variable determining the phase distribution of the molded parts.
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