On the detachment of patched panels under thermomechanical loading

Abstract

The problem of propagation of interfacial failure in patched panels subjected to temperature change and transverse pressure is formulated from first principles as a propagating boundaries problem in the calculus of variations. This is done for both cylindrical and flat structures simultaneously. An appropriate geometrically nonlinear thin structure theory is incorporated for each of the primitive structures (base panel and patch) individually. The variational principle yields the constitutive equations of the composite structure within the patched region and an adjacent contact zone, the corresponding equations of motion within each region of the structure, and the associated matching and boundary conditions for the structure. In addition, the transversality conditions associated with the propagating boundaries of the contact zone and bond zone are obtained directly, the latter giving rise to the energy release rates in self-consistent functional form for configurations in which a contact zone is present as well as when it is absent. A structural scale decomposition of the energy release rates is established by advancing the decomposition introduced in W. J. Bottega, Int. J. Fract. 122 (2003), 89-100, to include the effects of temperature. The formulation is utilized to examine the behavior of several representative structures and loadings. These include debonding of unfettered patched structures subjected to temperature change, the effects of temperature on the detachment of beam-plates and arch-shells subjected to three-point loading, and the influence of temperature on damage propagation in patched beam-plates, with both hinged-free and clamped-free support conditions, subjected to transverse pressure. Numerical simulations based on closed form analytical solutions reveal critical phenomena and features of the evolving composite structure. It is shown that temperature change significantly influences critical behavior.

On the Interaction of Thermally Induced Buckling and Debond Propagation in Patched Structures

“…For this work, we adopt the variational, moveable interior boundaries, formulation of Bottega and Carabetta [12]. All pertinent parameters are normalized in accordance with Bottega and Carabetta [12], wherein length scales are normalized with respect to the half-length of the baseplate and stiffnesses are normalized with respect to the bending stiffness of the baseplate and certain length parameters (see Appendix B).…”

“…All pertinent parameters are normalized in accordance with Bottega and Carabetta [12], wherein length scales are normalized with respect to the half-length of the baseplate and stiffnesses are normalized with respect to the bending stiffness of the baseplate and certain length parameters (see Appendix B). The structure of interest is composed of two substructures; a "baseplate" of half-span length L = 1 and a patch of half-span length Lp<L that is centrally adhered on top of the baseplate.…”

“…[12], which is the scale defined by Rutgerson and Bottega [20]. The corresponding nondimensional temperature change is then…”

“…[12] allows the "moveable" bond zone and contact zone boundaries {a and b, respectively) to vary arbitrarily as well as the displacements. This unique feature begets the transversality conditions.…”

“…The effect of a uniform temperature difference on the debonding behavior of patched structures (when simultaneously subjected to transverse pressure) was examined by Carabetta [11], where the presence of a temperature field was shown to impact the debonding threshold. Bottega and Carabetta [12] also studied the effect of temperature on debonding of patched structures, as well as other laminates (both flat and curved), with edges that are free to translate inplane. In that work, they established a unique mathematical formulation for the class of problem, using the calculus of variations.…”