In this study, the failure mechanism of sandwich-to-laminate T-joints under pull-off loading was investigated by experiment and the finite element method. A total of 26 T-joint specimens were manufactured and tested in order to investigate the effects of both adhesive thickness (0.4, 2.0, and 4.0 mm...
In this study, the failure mechanism of sandwich-to-laminate T-joints under pull-off loading was investigated by experiment and the finite element method. A total of 26 T-joint specimens were manufactured and tested in order to investigate the effects of both adhesive thickness (0.4, 2.0, and 4.0 mm) and environmental conditions on the failure of the joints. The results showed that failure occurred mainly as intralaminar failure in the first layer of the sandwich face, which was contacted to the paste adhesive. The failure load did not significantly change with increasing adhesive thickness in both RTD (Room Temperature and Dry) and ETW (Elevated Temperature and Wet) conditions. In the case of ETW conditions, however, the failure load increased slightly with an increase in adhesive thickness. The joints tested in ETW conditions had higher failure loads than those tested in RTD conditions. In addition to the experiment, a finite element analysis was also conducted to investigate the failure of the joint. The stress inside the first ply of the sandwich face was of interest because during the experiment, failure always occurred there. The analysis results showed good agreement with the trend of experimental results, except for the case of the smallest adhesive thickness. The highest stress was predicted in the regions where initial failure was observed in the experiment. The maximum stress was almost constant when the adhesive thickness was beyond 2 mm.
In this study, the failure mechanism of sandwich-to-laminate T-joints under pull-off loading was investigated by experiment and the finite element method. A total of 26 T-joint specimens were manufactured and tested in order to investigate the effects of both adhesive thickness (0.4, 2.0, and 4.0 mm) and environmental conditions on the failure of the joints. The results showed that failure occurred mainly as intralaminar failure in the first layer of the sandwich face, which was contacted to the paste adhesive. The failure load did not significantly change with increasing adhesive thickness in both RTD (Room Temperature and Dry) and ETW (Elevated Temperature and Wet) conditions. In the case of ETW conditions, however, the failure load increased slightly with an increase in adhesive thickness. The joints tested in ETW conditions had higher failure loads than those tested in RTD conditions. In addition to the experiment, a finite element analysis was also conducted to investigate the failure of the joint. The stress inside the first ply of the sandwich face was of interest because during the experiment, failure always occurred there. The analysis results showed good agreement with the trend of experimental results, except for the case of the smallest adhesive thickness. The highest stress was predicted in the regions where initial failure was observed in the experiment. The maximum stress was almost constant when the adhesive thickness was beyond 2 mm.
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가설 설정
The initial failure was observed in the first layer of the sandwich face as a visual crack at the region closed to the end of adhesive, as shown in Fig. 5. It is obvious that this region experienced a high stress concentration due to geometrical discontinuity.
The failure modes were dominated by the intralaminar failure of the first fabric layer of the sandwich face, as shown in Fig. 9. It was interesting that the failure loads of the joints in the ETW condition were higher than those in the RTD condition.
제안 방법
However, research on the environmental effects on the joints has been limited to the lap joint, and studies on adhesively bonded T-joints are rarely found. In this paper, therefore, an experiment was conducted to investigate the effects of environmental conditions on the failure of composite T-joints with different adhesive thicknesses. Two environmental conditions were considered: room temperature and dry (RTD) and elevated temperature and wet (ETW).
78 kN was applied to the T-shape steel part. It was the failure load of the 0.4 mm adhesive joint in the RTD condition and was applied to all T-joint models in order to compare the behavior of different joints under the same magnitude of load.
The study investigated the failure behavior of composite bonded T-joints in different environmental conditions (RTD and ETW). The test results demonstrated that the failure loads in the ETW condition increased compared to those in the RTD cases while adhesive properties decreased in the ETW condition.
They investigated the strain distribution in the joints under tensile pull-out loads and determined the presence and the extent of disbonds. The work dealt with a real time structural monitoring system capable of determining the presence, location, and the extent of damage in a composite structure. Artificial neural networks were used to determine damage development.
[8] related to the damage detection of T-joints. They investigated the strain distribution in the joints under tensile pull-out loads and determined the presence and the extent of disbonds. The work dealt with a real time structural monitoring system capable of determining the presence, location, and the extent of damage in a composite structure.
대상 데이터
A carbon/epoxy fabric pregreg from Toray America (T700SC-12KC/#2510) was used to manufacture the composite parts. The composite laminates attached to the steel part had a stacking sequence of [45/0]6.
성능/효과
The test results demonstrated that the failure loads in the ETW condition increased compared to those in the RTD cases while adhesive properties decreased in the ETW condition. In the test results, there was no remarkable trend between the failure load and adhesive. Even though the failure load slightly increased along with the adhesive thickness in the ETW conditions, the difference was no more than 6%.
The study investigated the failure behavior of composite bonded T-joints in different environmental conditions (RTD and ETW). The test results demonstrated that the failure loads in the ETW condition increased compared to those in the RTD cases while adhesive properties decreased in the ETW condition. In the test results, there was no remarkable trend between the failure load and adhesive.
참고문헌 (13)
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Fenske, M.T. and Vizzini, A.J.,"The inclusion of inplane stresses in delamination criteria", Journal of Composite Materials, Vol. 35, 2001, pp.1325-1342.
Tomblin, J., Sherraden, J., Seneviratne, W., and Raju, K.S., "A-Basis and B- Basis Design Allowables for Epoxy-Based Prepreg TORAY T700GC-12K-31E/#2510 Unidirectional Tape", Advanced General Aviation Transport Experiments, AGATE-WP3.3-033051-132, November 2002.
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