OPTIMUM BI-ADHESIVE ZONING IN BONDED LAP JOINTS BETWEEN COAXIAL CIRCULAR CYLINDRICAL SHELLS

Date

2026-9-02

Author

Acarer, Muhammed Yusuf

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Stress concentrations near overlap ends limit adhesively bonded coaxial tubular lap joints. This thesis develops a linear-elastic, quasi-static variational model for a flexible-stiff-flexible bi-adhesive bondline within first-order shear deformation shell theory. Fourier harmonics represent circumferential dependence, Legendre spectral elements discretise the axial domain, and an equivalent elastic interlayer transfers adhesive tractions. The implementation recovers the all-stiff limit, agrees with an independent transfer-matrix solution using the same assumptions within 0.03% for peak shear and 0.42% for peak tensile peel, and is assessed against an axisymmetric finite-element benchmark. Axial tension and internal pressure are considered; the latter represents a cylindrical section restrained at its remote ends without end-cap thrust. For Araldite AV138/Sikaforce 7752, the peak-stress minimax objective gives flexible end zones of 90.9 mm per edge under tension and 59.1 mm under pressure. Relative to the better mono-adhesive reference, the model predicts peak shear and tensile-peel reductions of 4.9% and 6.8% under tension, and 5.3% and 4.6% under pressure. A secondary capacity-normalised demand objective, used for comparison rather than as a failure criterion, gives 14.1 and 13.7 mm. Neither the peak-stress nor the capacity-normalised optimum dominates both measures. For a reduced adhesive family with modulus ratio m and strength ratio s, s > m is necessary but not sufficient for zoning to outperform both mono-adhesive references. Preferred zoning therefore depends on the objective and load case. The improvements are model-predicted trends, not experimentally validated strength gains.

Subject Keywords

Adhesively bonded joint, Bi-adhesive bondline, Cylindrical shell, First-order shear deformation theory, Spectral element method

URI

https://hdl.handle.net/11511/121023

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Graduate School of Natural and Applied Sciences, Thesis