Papers by Keyword: Adhesive Bonding

Abstract: A solid propellant microthruster array consists of three parts (five layers) was designed to form propulsion system of nanosatellite. The layers of the array were fabricated by different MEMS technique respectively. Then the array was assembled by adhesive bonding (H70E thermal epoxy). An initial test was operated with the ignition test stand composed of high speed video system, electronic power source, and oscilloscope. A constant voltage was applied to the igniters through two probes contact with the pad of ignition circuitry. The test indicates that the microthruster array can be ignited under 15V.

Abstract: Shear stress distribution behaviour of a single-lap bonded joint under tension was investigated using the three-dimensional finite element methods. Five layers of 20-node solid elements were used across the adhesive layer thickness to get accurate indication of the variation of shear stress. The stress distributions in the joint are given by the stress contours. All the numerical results obtained from the finite element analysis show that the spatial distribution of shear stress are similar for all 6 interfaces though the stress values are obviously different. It can also be seen from the results that the left hand region is subjected to very high stress.

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 different geometric sizes, different adhesive thickness and different surface treatments have great influence on the properties of aluminum alloy 6063 bonding joints. This paper takes single lap joint for object, adopts the tensile shear test, takes the tensile shear strength as the judgment basis, and exploresthe variation inperformance of aluminum alloy 6063 bondingjoints. The test results show that: Aluminum alloy 6063 bonding joints occur serrated yielding phenomenon inthe tensile shear test; In a certain layer thickness range, tensile shear strength of aluminum alloy 6063 bondingjoints correspondingly increaseswiththe thickness of samples increasing; Different surface treatments on aluminum alloy 6063 have a great influence on tensile-shear strength, and mechanical polishing and skim can significantly improve tensile shear strength of aluminum alloy 6063 bonding joints.

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: This paper investigates normal stress distribution of a single-lap adhesively bonded joint under tension using the three-dimensional finite element methods. Five layers of solid elements were used across the adhesive layer thickness in order to obtain an accurate indication of the variation of normal stress. All the numerical results obtained from the finite element analysis show that the spatial distribution of normal stress are similar for different interfaces though the stress values are obviously different. It can also be seen from the results that the left hand region, which is very close to the left free end of the adhesive layer, is subjected to very high stress and the magnitude of the normal stress oscillates in value close to the left end of the adhesive layer.

Abstract: This paper presents a method of low temperature wafer level adhesive bonding using non-photosensitive bisbenzocyclobutene (BCB) from Dow Co for resonant pressure sensor package. The bonding process is performed at the temperature below 250oC, with the pressure on the wafer 2-3 Bar in vacuum in a wafer bonding system. According to the bonding process, pre-bake time, pumping time, pressure placed on the sensor and the thickness of cross-linked layer are the most important factors. Experiments show that more than 95% of the area is successfully bonded, the hermeticity maintains well after thermal shock and long term tests, and the tensile strength of the fabricated bonds is up to 40MPa. The bonding technique was successfully tested in the fabrication process of resonant pressure sensor, and the results show that this bonding technique is a viable MEMS encapsulation technology for hermetically cavity sealing.

Abstract: In this paper, starting from analytic relations presented in literature, a more general approach was obtained in order to evaluate the load capacity of single strapped joints in the cases when the adherends are right or tapered in the overlap zone. Two distinct loading cases, in tension and in bending, are considered. The analytical relations were validated by nonlinear finite element analyses. The comparison with the similar results of the linear analyses emphasized that only the nonlinear approach is appropriate to study the stress states in unsymmetrical joints, even if the adhesive can be considered as an isotropic and homogenous material. For design purposes, the influence of some geometrical parameters on the stress state in the joint was also evaluated.

Abstract: Natural fiber based bio-composites are gaining prime importance these days because of their high strength to weight ratio and environmental benefits. An increase in the application spectrum of these materials necessitates cost effective high quality processing in order to meet the stringent design requirements. In the present investigation, fully biodegradable natural fiber (grewia optiva) reinforced poly lactic acid (PLA) composite has been developed. The tensile strength of the composite has been found to increase by 75% of that of the neat polymer. The developed composites have been joined using the adhesive bonding and the microwave joining. The tensile shear strength of the joint has been experimentally evaluated and it has been found that the bond strength of adhesively bonded specimen (4.9% of the parent material strength) is substantially lower as compared to microwave joined specimen (62.85% of the parent material strength). The process of microwave joining has also been simulated using standard Multiphysics software and the results were in close agreement with the experimentally recorded values.