Characterizing the constitutive properties and developing a stress model for adhesive bond-line readout

Patankar, Kshitish A.; Dillard, David A.; Fernholz, Kedzie D.

doi:10.1016/j.ijadhadh.2012.07.006

“…The process-induced strains of autoclave-cured composite parts have been extensively studied in the literature [1][2][3][4][5][6][7][8][9][10][11] but the influence of the adhesive during autoclave-bonding of composite laminates has often been disregarded. However, research on aeronautic repair processes [12][13][14] and exterior automotive panels [15][16][17][18][19][20] have proved that adhesives may generate some noticeable strains for composite-metallic and composite-composite bonded assemblies. Some authors have studied the simulation of cure-induced strains and stresses of integrated composite material structures, but usually disregard the influence of the adhesive film [21,22].…”

Section: Introductionmentioning

confidence: 99%

Experimental study and in-situ FBG monitoring of process-induced strains during autoclave co-curing, co-bonding and secondary bonding of composite laminates

Moretti

¹

,

Olivier

²

,

Castanié

³

et al. 2021

Composites Part A: Applied Science and Manufacturing

View full text Add to dashboard Cite

The geometric stability of bonded structural parts, such as self-stiffened panels, is a critical issue in aeronautics.However, autoclave curing and bonding of large complex integrated primary structures often induce distortions compromising their geometric stability. Composite cure-induced strains and distortions have been extensively studied in the literature but the influence of the adhesive on these distortions has often been overlooked. More experimental data are therefore necessary to properly understand its influence on process-induced strains and its behaviour during cure. The present paper reports a wide range of new experimental investigations showing the non-negligible influence of the adhesive on cure-induced distortions of composite assemblies. The experimental data presented include postcure distortion measurements, optical microscope imaging, micro-tomography imaging and FBG in-situ strain monitoring during an autoclave bonding process. These experiments demonstrate the impact of the adhesive film behaviour and of the manufacturing bonding process on final distortions and strains of composite assemblies.

show abstract

“…4). Compared with other structures, such as bimaterial [10] and bonded substructure [14], mechanical strain caused by the CTE and stiffness difference of inner and outer panels is dominant. The direction and size of shear stress in the upper and lower adhesive layers change along the y-axis, which is related to asymmetric structure.…”

Section: Discussionmentioning

confidence: 98%

“…Compared with other structures, such as bimaterial [10] and bonded substructure [14], mechanical strain caused by the difference of material properties plays an important role.…”

Section: Deformation Process Of the Sandwich Structurementioning

confidence: 99%

See 1 more Smart Citation

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.

show abstract

“…In early studies, linear model [8][9] was mainly used in the adhesive-bonded structure. As it can not describe the stress relaxation phenomenon, viscoelastic model [10] was gradually adopted. These models ignored the curing properties of the adhesive and assumed that the structure was in stress-free state before cooling.…”

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

2

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.

show abstract

Characterizing the constitutive properties and developing a stress model for adhesive bond-line readout

Cited by 11 publications

References 18 publications

Experimental study and in-situ FBG monitoring of process-induced strains during autoclave co-curing, co-bonding and secondary bonding of composite laminates

Experimental study and in-situ FBG monitoring of process-induced strains during autoclave co-curing, co-bonding and secondary bonding of composite laminates

Numerical and Experimental 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

Contact Info

Product

Resources

About