Closed/Semi-Closed Form Solutions for Face/Core Debonds in Sandwich Beams

Niranjan Babu, Siddarth

Title:

Closed/Semi-Closed Form Solutions for Face/Core Debonds in Sandwich Beams

dc.contributor.advisor	Kardomateas, George A.
dc.contributor.author	Niranjan Babu, Siddarth
dc.contributor.committeeMember	McDowell, David
dc.contributor.committeeMember	Rimoli, Julian
dc.contributor.committeeMember	Kennedy, Graeme
dc.contributor.committeeMember	Di Leo, Claudio
dc.contributor.department	Aerospace Engineering
dc.date.accessioned	2022-05-18T19:37:14Z
dc.date.available	2022-05-18T19:37:14Z
dc.date.created	2022-05
dc.date.issued	2022-05-03
dc.date.submitted	May 2022
dc.date.updated	2022-05-18T19:37:14Z
dc.description.abstract	Sandwich beams are highly susceptible to debonding at the interface between face and core. These debonds can grow and eventually lead to complete failure of the structure. To understand and study such debonds analytically, an Elastic Foundation Analysis (EFA) can be used to incorporate the effects of crack tip deformation in beam theory. In this model, EFA is extended further to better capture the effects of transverse shear. Unlike most models, this approach can be applied for both isotropic and orthotropic face & core materials. The approach uses both normal and rotational springs in the elastic foundation in the bonded region of the beam to capture transverse shear effects. Timoshenko beam theory introduces a rotational degree of freedom to the beam element and the rotational springs are used to capture it. The model is comprehensive and include both the deformation of the debonded part and the substrate. Double Cantilever Beam (DCB) and Single Cantilever Beam (SCB) specimens are chosen to demonstrate the procedure to obtain Mode-I fracture parameters. In the case of Mode-II fracture, the effects of crack face contact can affect the fracture parameters and are usually neglected in analytical approaches. The proposed model extends EFA by introducing a tensionless spring foundation in the cracked region. Tensionless springs are used to capture the compressive stresses across the interface between the debonded face sheet and the substrate. The absence of tensile stresses in the foundation is because when there is tension the debonded face sheet lifts away from the substrate. Apart from compressive stresses, there will also be frictional forces acting between the crack faces. So, the governing equations are modified to capture the friction tractions in the crack faces. An End Notched Flexure (ENF) specimen is chosen to demonstrate Mode-II fracture. Expressions for energy release rates are obtained using J-Integral approach and it is modified to capture the energy lost due to the friction tractions. Solutions for mode partitioning are obtained using the axial and transverse displacements near the crack tip. Results obtained from these expressions are compared with results from finite element models. The model is comprehensive, efficient and would provide accurate results when compared with the other models (from literature).
dc.description.degree	Ph.D.
dc.format.mimetype	application/pdf
dc.identifier.uri	http://hdl.handle.net/1853/66625
dc.publisher	Georgia Institute of Technology
dc.subject	Sandwich beams
dc.subject	Debonds
dc.subject	Elastic foundation
dc.subject	crack contact
dc.title	Closed/Semi-Closed Form Solutions for Face/Core Debonds in Sandwich Beams
dc.type	Text
dc.type.genre	Dissertation
dspace.entity.type	Publication
local.contributor.advisor	Kardomateas, George A.
local.contributor.corporatename	Daniel Guggenheim School of Aerospace Engineering
local.contributor.corporatename	College of Engineering
local.relation.ispartofseries	Doctor of Philosophy with a Major in Aerospace Engineering
relation.isAdvisorOfPublication	e62aa2d0-7baf-43bf-8754-3a984802bb90
relation.isOrgUnitOfPublication	a348b767-ea7e-4789-af1f-1f1d5925fb65
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thesis.degree.level	Doctoral