Face/Core Disbonding Fracture of Honeycomb Core Sandwich Panels

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" Face/Core Disbonding Fracture of Honeycomb Core Sandwich Panels "
Tauhiduzzaman, Mohammad Carlsson, Leif A.

Document Type	:	Latin Dissertation
Language of Document	:	English
Record Number	:	1105862
Doc. No	:	TLpq2333949749
Main Entry	:	Carlsson, Leif A.
	:	Tauhiduzzaman, Mohammad
Title & Author	:	Face/Core Disbonding Fracture of Honeycomb Core Sandwich Panels\ Tauhiduzzaman, MohammadCarlsson, Leif A.
College	:	Florida Atlantic University
Date	:	2019
student score	:	2019
Degree	:	Ph.D.
Page No	:	154
Abstract	:	The objective of the research presented in this thesis is to develop analysis and test procedures for the characterization of disbonding crack growth in a honeycomb (HC) core sandwich structure. Face sheet-to-core disbonding are of particular interest to aircraft certification authorities due to several in-service occurrences. Experimental investigation was initially focused on the mode I dominated Single Cantilever Beam (SCB) test method. Various data reduction methodologies were employed to determine the fracture toughness. The MBT method produced the most consistent and conservative results. Finite element analysis (FEA) a double periodic array of hexagonal cells was conducted to determine the effective in-plane extensional modulus and Poisson ratio of the HC core. It was shown that deformation constraints on the core, due to attachment of the core to rigid face sheets, will drastically change the behavior of the HC core. The response changes from being governed by bending to stretching which substantially elevates the effective in-plane modulus. Fracture mechanics analysis of a face/core interface crack in a HC core SCB specimen was performed using FEA. The influence of in-plane properties of the constrained core on energy release rate and mode mixity phase angle was examined. Use of plane strain conditions and an elevated modulus of the constrained core in the analysis is recommended. The approach is substantiated by testing of HC core SCB sandwich. Test results showed good agreement with FEA prediction of compliance and kink angle. Mode II interface fracture of HC core sandwich is examined using End Notch Flexure (ENF) test. Beam analysis of the ENF sandwich specimen is used to design the test to achieve disbonding prior to other failure modes such as crack propagation, face indentation, core crush and core compression failure. The stability of crack propagation and the influence of friction were also investigated. In-plane compression tests on HC core specimens with a range of cell sizes and density were performed to determine the compressive response and crushing strength. Overall, predictions from the failure loads and parametric analysis guides the selection of suitable test geometry of ENF specimen to achieve the desired disbonding failure mode.
Subject	:	Aerospace engineering
	:	Engineering
	:	Mechanical engineering