Modeling Thermal Residual Stresses in Composite Patch Repairs During Multitemperature Bonding Cycles

Cho, J.; Sun, C. T.

doi:10.2514/2.7211

“…On the contrary, the higher the heating rate, the higher the gel temperature. When the heating rate exceeds a certain value, as the 8 K/min, the adhesive is bonded to the panels in the heat holding stage, and the overall deformation value is the maximum [13]. Then, the development process of surface deformation of the outer panel and internal stress of the adhesive layer is analyzed, and the influence of temperature cycle on the maximum deformation of the component is discussed.…”

Section: Influence Of Curing Temperature Cyclesmentioning

confidence: 99%

“…These models ignored the curing properties of the adhesive and assumed that the structure was in stress-free state before cooling. However, subsequent studies showed that many factors, such as curing temperature [11], curing rate [12], and multi-step method [13], could affect the final results. It can be seen that neglecting the mechanical properties of the adhesive in the heating and holding stage was easy to lead to large prediction deviation.…”

Section: Introductionmentioning

confidence: 99%

Numerical study on curing-induced residual stress and deformation of adhesively bonded sandwich structures of dissimilar materials

Li

¹

,

Zhu

²

,

Li

³

et al. 2022

Int J Adv Manuf Technol

1

0

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Adhesively bonded sandwich structure with dissimilar materials becomes an important means of lightweight for the next generation of autobody closure panels. However, during the baking process, the complicated change of physical properties of the adhesive can lead to structural mismatch deformation. In this paper, a multi-physics coupling numerical model of one-component hemming adhesive during the curing process is proposed, to reveal the deformation mechanism of adhesively bonded sandwich structures quantitatively. The material constitutive model of the hemming adhesive is established, considering evolution of curing properties. The curing process of typical aluminum alloy and steel bonded sandwich structure is simulated in COMSOL Multiphysics. The predicted surface deformation of the component is verified by experiment using Digital Image Correlation (DIC) technique, which captures the full-field displacement in a non-intrusive manner. Then, the development process of surface deformation of the outer panel and residual internal stress of the adhesive layer is analyzed, and the influence of temperature cycle on the maximum deformation of the component is discussed. The results show at the beginning of holding stage, the deformed component slightly rebounds, which is related to the chemical shrinkage. Mechanical strain caused by the coefficient of thermal expansion (CTE) and stiffness difference of the inner and outer panels is dominant in the adhesive layer. Reducing the curing rate and maximum holding temperature can reduce the overall deformation of the structure.

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“…On the contrary, the higher the heating rate, the higher the gel temperature. When the heating rate exceeds a certain value, as the 8 K/min, the adhesive is bonded to the panels in the heat holding stage, and the overall deformation value is the maximum [13]. Adjusting the curing kinetics characteristics of the adhesive layer can reduce the structural deformation, but it may prolong the curing time.…”

Section: Influence Of Curing Temperature Cyclesmentioning

confidence: 99%

Numerical and Experimental Study on Curing-induced Residual Stress and Deformation of Adhesively Bonded Sandwich Structures of Dissimilar Materials

Li

¹

,

Zhu

²

,

Li

³

et al. 2021

Preprint

0

View full text Add to dashboard Cite

Adhesively bonded sandwich structure with dissimilar materials becomes an important means of lightweight for the next generation of autobody closure panels. However, during the baking process, the complicated change of physical properties of the adhesive can lead to structural mismatch deformation. In this paper, a multi-physics coupling numerical model of one-component hemming adhesive during the curing process is proposed, to reveal the deformation mechanism of adhesively bonded sandwich structures quantitatively. The material constitutive model of the hemming adhesive is established, considering evolution of curing properties. The curing process of typical aluminum alloy and steel bonded sandwich structure is simulated in COMSOL Multiphysics. The predicted surface deformation of the component is verified by experiment using Digital Image Correlation (DIC) technique, which captures the full-field displacement in a non-intrusive manner. Then, the development process of surface deformation of the outer panel and residual internal stress of the adhesive layer is analyzed, and the influence of temperature cycle on the maximum deformation of the component is discussed. The results show at the beginning of holding stage, the deformed component slightly rebounds, which is related to the chemical shrinkage. Mechanical strain caused by the coefficient of thermal expansion (CTE) and stiffness difference of the inner and outer panels is dominant in the adhesive layer. Reducing the curing rate and maximum holding temperature can reduce the overall deformation of the structure.

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“…In many papers, only the cooling stage is considered, i.e., stresses arising during the heating process are unreasonably neglected. An exception is [36], where the stress-strain behaviour is determined, taking into account the previously developed kinetic model of the binder performance in the curing process, as well as [34,35], providing the model for behaviour of viscoelastic material to describe the PCM operation in the manufacturing process, including the processes of formation, polymerization, and development of residual deformations and stresses.…”

Section: Introductionmentioning

confidence: 99%

Effects of the Temperature–Time Regime of Curing of Composite Patch on Repair Process Efficiency

Kondratiev

¹

,

Píštěk

²

,

Smovziuk

³

et al. 2021

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Repair procedures with the use of composite patches are considered to be the most effective among the current technologies of repair of the structures of various applications. In the process of moulding-on of a patch made of polymeric composite material by means of curing, technological stresses arise in the patch. Determination of residual technological stresses is a priority task for the modelling of the repair process. Reduction of residual stresses can be achieved by optimization of the mode of repair patch curing. For meeting this objective, the method for determination of technological stresses, which arise in the structure under repair in the process of curing of a composite patch, has been developed. The method takes into account the shrinkage, change in physico-mechanical characteristics, rheological processes occurring in the binder during moulding process, and determination of stresses in the structure under repair at any time. Therefore, premature failure of the repair joint at the stage of repair can be avoided. It is shown that the method adequately describes the level of deformations and stresses in the structure being repaired at the stage of heating and holding of the composite patch. Increase in the moulding temperature leads to a reduction in residual stresses in the structure under repair. However, current stresses at the stages of heating and temperature holding are increased significantly. Reliability of assumptions and developed method is confirmed by the comparison with the experimental data. The obtained experimental graph of total deformation of the composite patch allowed us to clearly determine the moment of residual stress occurrence in the structure under repair. This moment matches quite exactly (with the discrepancy not exceeding 5 min) the gel point determined analytically based on dependence of the degree of curing on the moulding mode. Consequently, the research together with the results previously obtained allows making an integrated choice of geometric parameters of the repair composite patch and temperature–time regime of its curing in order to ensure the specified level of strength and stiffness of the structure under repair.

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Modeling Thermal Residual Stresses in Composite Patch Repairs During Multitemperature Bonding Cycles

Cited by 3 publications

References 4 publications

Numerical study on curing-induced residual stress and deformation of adhesively bonded sandwich structures of dissimilar materials

Numerical study on curing-induced residual stress and deformation of adhesively bonded sandwich structures of dissimilar materials

Numerical and Experimental Study on Curing-induced Residual Stress and Deformation of Adhesively Bonded Sandwich Structures of Dissimilar Materials

Effects of the Temperature–Time Regime of Curing of Composite Patch on Repair Process Efficiency

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