Papers by Author: Jian Guang Zhang

Abstract: 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.

Abstract: The response of adhesively bonded joints subjected to a transverse impact was investigated. The joints were bonded by two-part acrylic adhesive DP8005 with using two types of adherents, polypropylene and glass fiber reinforced polypropylene. The lap joints were impacted by a drop weight with hemisphere tip at a low velocity. An energy model was applied to evaluate the effect of the properties and thickness of adherents on the impact strength of the joints. The results from model showed good agreement with those from experiments.

Abstract: 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.

Abstract: In ultrasonic welding of fiber reinforced thermoplastic, heat is generated by means of interfacial friction at the interface to be bonded and internal friction of the polymer chains. A finite element model, using ANSYS software, was developed to calculate the transient temperature profile in glass fiber reinforced polypropylene joint in the transverse direction during ultrasonic welding. The results showed that the temperature in the joint increased with increasing weld time. With higher weld pressure, the temperature of molten point of polyprolylene can be reached within a shorter weld time. The weld map obtained from the finite model was in agreement with the results obtained experimentally.

Abstract: Glass fiber reinforced polypropylene composites were joined by ultrasonic welding, employing various weld conditions. Single-lap shear testing was used to evaluate the effect of weld time and weld pressure on the weld performance. The weld strength increased with increasing weld time and weld pressure until a plateau or maximum strength was reached. The required weld time to obtain a complete weld became shorter when the weld pressure was increased. As lower weld pressure was applied, a complete weld could not be obtained unless relatively longer weld times were employed. A welding map, showing conditions of weld time and weld pressure to get a good weld, was obtained.

Abstract: Joining behavior of long glass fiber reinforced polypropylene (LFT) by three types of adhesive was investigated. Single-lap shear testing was used to evaluate the performance of adhesively bonded structures. The two-part acrylic adhesive DP8005 was determined to be the best among the three adhesive candidates, which was attributed to its low surface energy. The stress distribution in the adhesive layer of the single lap joint was modeled by static elastic analysis using ANSYS software. The shear and peel stresses peaked at the edges of the adhesive layer.

Abstract: This study presents an effective methodology for the optimum design of two-component armor. The armor consists of two plates: one is boron carbide ceramic and the other is kevlar/epoxy composites. The effect of the thickness of two plates on the ballistic limit velocities of the armor was investigated by Florence model. A finite element model was created using MSC.DYTRAN to simulate the impact of a rigid projectile on the composite armor. The optimum thickness of the ceramic and composite was obtained by evaluating the ballistic resistance efficiency.

Abstract: 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).