Sn3.0Ag3.0Bi3.0In (SABI333) solder is easy to form solder joints with different crystal structures during solidification. Solder joints with different crystal structures can exhibit different failure behaviors during ...
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Sn3.0Ag3.0Bi3.0In (SABI333) solder is easy to form solder joints with different crystal structures during solidification. Solder joints with different crystal structures can exhibit different failure behaviors during creep. Five kinds of SABI333 solder joints with different crystal structures were selected to study the effect of grain boundary on the failure behavior of creep. The scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) were utilized to characterize the surface morphologies and crystal orientations of solder joints. When there were only low angle grain boundaries or twin boundaries in the solder joints, it was not easy to generate cracks inside the solder joints during creep but easy to generate cracks at the interfaces between the copper bars and solder matrices. However, when there were high angle grain boundaries greater than 70 degrees in the solder joints, the cracks would propagate along such grain boundaries during creep. This phenomenon depends on the difference of grain boundary energy and the difference of deformation degrees of grains on both sides of grain boundaries during creep. The grain boundary energy of the high angle grain boundaries is relatively high and the deformation degrees of grains on both sides of high angle grain boundaries are quite different during creep. This research is conducive to further understand the creep failure behavior of SABI333 solder joints under the service environment.
Durability is a critical concern for concrete structures externally bonded with fiber-reinforced polymer reinforcement. This paper presents the results from an experimental study which compared the bond durability of ...
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Durability is a critical concern for concrete structures externally bonded with fiber-reinforced polymer reinforcement. This paper presents the results from an experimental study which compared the bond durability of epoxy-bonded CFRP sheets and cement-bonded CFRP grids to concrete interfaces subjected to water immersion. Totally twelve groups of CFRP sheet or grid-strengthened concrete beams with a notch at their midspan were carefully fabricated through epoxy- and cement-based bonding systems and tested under monotonic loading before and after water immersion exposure, respectively. The cement binder included polymer cement mortar (PCM) and ductile engineered cementitious composite (ECC). The CFRP grids and sheets were designed with the similar tensile stiffness. The duration of water immersion ranged from 0 to 6 months. The test results indicated that debonding in concrete adjacent to the concrete-adhesive interface in accompany with a diagonal concrete crack near the notch was the main failure mode of the beams strengthened with epoxy-bonded CFRP sheet and ECC-bonded CFRP grid, while the tearing off of CFRP grids from the PCM matrix was the main failure mode of the beams strengthened with PCM-bonded CFRP grids. After water immersion exposure, the ultimate loads of the beams with cement-based CFRP grids were at least 50% higher than their epoxy-bonded counterparts, confirming the superior moisture durability of cement based bond to epoxy-bonded ones. The interfacial fracture energy was found to exhibit an exponential decline trend with water immersion duration.
This paper presents the results from a comparative study on the residual bond performance of epoxy and cementbonded carbon fiber-reinforced polymer (CFRP) reinforcement to concrete interfaces that experienced differen...
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This paper presents the results from a comparative study on the residual bond performance of epoxy and cementbonded carbon fiber-reinforced polymer (CFRP) reinforcement to concrete interfaces that experienced different levels of elevated temperature exposure. In total twelve groups of concrete beams strengthened with CFRP sheet and grids of the same tensile stiffness, through epoxy and cement-based adhesive bonding, respectively, were carefully prepared and exposed to different test temperature levels from 20 degrees C to 600 degrees C. Both polymer cement mortar (PCM) and ductile engineered cementitious composite (ECC) were adopted as the cement binder. The strengthened beams were tested under three-point monotonic bending after different levels of elevated temperature exposure. It was found that with increasing the exposure temperature, the failure modes of the strengthened beams shifted from debonding in a thin layer of concrete substrate to debonding near the fiberadhesive interface and tearing off of CFRP grids from the ECC matrix. The peak loads of concrete beams strengthened with cement-bonded CFRP grids are at least 50% higher than their counterparts strengthened with epoxy-bonded CFRP sheets given the same temperature exposure.
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