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Article
Publication date: 6 February 2017

Roman Ruzek, Martin Kadlec, Konstantinos Tserpes and Evaggelos Karachalios

Compression is critical loading condition for composite airframes. Compression behaviour of structures with or without damages is a weak point for composite fuselage…

Abstract

Purpose

Compression is critical loading condition for composite airframes. Compression behaviour of structures with or without damages is a weak point for composite fuselage panels. This is one of the reasons for need of continuous in-service health monitoring of composite structures. The purpose of this paper is to characterize the compression panel behaviour on the base of a developed and implemented structural health monitoring (SHM) system.

Design/methodology/approach

The SHM system based on fibre optic Bragg grating (FOBG) sensors and standard resistance strain gauges (SGs) was placed onto/into (embedded or bonded) three stiffened carbon fibre reinforced polymer (CFRP) fuselage panels. The FOBG sensor system was used to monitor the structural integrity of the reference, impacted, and fatigued panels under compression loading. Both barely visible impact damage and visible impact damage were created to evaluate their influence on the panel behaviour. The functionality of the SHM system was verified through mechanical testing.

Findings

Experimental data showed the presence of impact damages significantly changes the buckling modes development and deformation behaviour of the panels. Some differences between the optical and SG sensors during buckling were observed. The buckling waves and failure development were very well indicated during loading by all sensors located on the panel surface but not by the embedded sensors. Good agreement between the data from the SGs and FOBG sensors was achieved for all sensors placed on the stringers, which did not buckle. The good reliability of FOBG sensors during the fatigue and static testing up to panel failure was verified.

Originality/value

The paper gives information about different buckling behaviour of CFRP fuselage stiffened panels in compression. The paper gives detailed information about measured signals from different sensors based on their location on/in the panel structure for realistic loading scenario of composite aerostructures. The paper gives an integrated overview of sensors placement considering possibilities to predicate structure behaviour.

Details

International Journal of Structural Integrity, vol. 8 no. 1
Type: Research Article
ISSN: 1757-9864

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Article
Publication date: 12 March 2019

Jakub Šedek and Roman Růžek

The purpose of this paper is to present a methodology for the determination of the stiffness when using simplified substitutive model of the joint. The usage of detailed…

Abstract

Purpose

The purpose of this paper is to present a methodology for the determination of the stiffness when using simplified substitutive model of the joint. The usage of detailed finite element (FE) model of the joint in complex assemblies is not convenient; therefore, the substitutive model of the joint is used in FE models.

Design/methodology/approach

The detailed and simplified FE model of the joint is created in ABAQUS software and the analysis as well. The results of displacements are used for the determination of the stiffness of connecting element in simplified substitutive FE model. The approach is presented based on the general view on the different regions in the joint.

Findings

A simple FE modelling approach for the joint including the equivalent stiffness is presented. The particular solution is performed for Magna-Lok type of the rivet. The results show the same displacement for the detailed and simplified FE models. The analytical formula for stiffness determination in the load case with minimal secondary bending is introduced.

Practical implications

The approach for stiffness determination is straightforward and so no stiffness “tuning” is necessary in the simplified FE model.

Originality/value

The new approach for definition of simple FE model of the joint is introduced. It is not necessary to model a complex structure with detailed joints. The equivalent stiffness can be determined by presented procedure for every joint without limitation of the type.

Details

Aircraft Engineering and Aerospace Technology, vol. 91 no. 6
Type: Research Article
ISSN: 1748-8842

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Article
Publication date: 14 October 2019

Jakub Šedek, Roman Růžek and Vladislav Oliva

The purpose of this paper is to deal with the FE analysis of strain constraint around the crack tip under cyclic loading and its utilization using crack growth prediction…

Abstract

Purpose

The purpose of this paper is to deal with the FE analysis of strain constraint around the crack tip under cyclic loading and its utilization using crack growth prediction strip yield model (SYM). During cycling, the constraint develops based on the load history. The monotonic loading is analyzed mostly, but during cyclic loading the conditions are different. The constraint is analyzed after several loading cycles applied in upwards part of the cycle and the formula for its development is proposed.

Design/methodology/approach

The study is based on the 3D FE analysis of middle-cracked tension specimen M(T). The strain constraint is described by Newman’s factor α. The variability of constraint factor α was analyzed for several load levels and specimen thicknesses. The crack is considered as non-propagating with straight crack front. The material is modelled as elastic-perfectly plastic. The SYM is modified by implementing variable constraint and the experimental results are compared with the simulation.

Findings

In major part of the loading cycle, it was found by FE analysis, that the constraint factor αg is lower after overloads than when creating monotonic plastic deformation on the same load level. The value of αg is governed by the ratio of thickness B over the plastic zone size rp. By implementing the variable constraint factor into the SYM, the improvement of the predicted specimens lives under variable amplitude loading was shown.

Originality/value

The new phenomenon on the variability of strain constraint during cyclic loading is presented. The development of constraint factor αg during cyclic loading is different from the monotonic loading and should be accordingly implemented into prediction models.

Details

International Journal of Structural Integrity, vol. 11 no. 5
Type: Research Article
ISSN: 1757-9864

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Article
Publication date: 10 August 2015

Jirí Behal, Petr Homola and Roman Ružek

The prediction of fatigue crack growth behaviour is an important part of damage tolerance analyses. Recently, the author’s work has focused on evaluating the FASTRAN…

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Abstract

Purpose

The prediction of fatigue crack growth behaviour is an important part of damage tolerance analyses. Recently, the author’s work has focused on evaluating the FASTRAN retardation model. This model is implemented in the AFGROW code, which allows different retardation models to be compared. The primary advantage of the model is that all input parameters, including those for an initial plane-strain state and its transition to a plane-stress-state, are objectively measured using standard middle-crack-tension M(T) specimens. The purpose of this paper is to evaluate the ability of the FASTRAN model to predict correct retardation effects due to high loading peaks that occur during variable amplitude loading in sequences representative of an aircraft service.

Design/methodology/approach

This paper addresses pre-setting of the fracture toughness K R (based on J-integral J Q according to ASTM1820) in the FASTRAN retardation model. A set of experiments were performed using specimens made from a 7475-T7351 aluminium alloy plate. Loading sequences with peaks ordered in ascending-descending blocks were used. The effect of truncating and clipping selected load levels on crack propagation behaviour was evaluated using both experimental data and numerical analyses. The findings were supported by the results of a fractographic analysis.

Findings

Fatigue crack propagation data defined using M(T) specimens made from Al 7475-T7351 alloy indicate the difficulty of evaluating the following two events simultaneously: fatigue crack increments after application of loads with maximum amplitudes that exceeded J Q and subcritical crack increments caused by loads at high stress intensity factors. An effect of overloading peaks with a maximum that exceeds J Q should be assessed using a special analysis beyond the scope of the FASTRAN retardation model.

Originality/value

Measurements of fatigue crack growth on specimens made from 7475 T7351 aluminium alloy were carried out. The results indicated that simultaneously evaluating fatigue crack increments after application of the load amplitude above J Q and subcritical increments caused by the loads at high stress intensity factors is difficult. Experiments demonstrated that if the fatigue crack reaches a specific length, the maximal amplitude load induces considerable crack growth retardation.

Details

International Journal of Structural Integrity, vol. 6 no. 4
Type: Research Article
ISSN: 1757-9864

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Article
Publication date: 13 April 2015

Roman Ružek, Radek Doubrava and Jan Raška

Various types of damage or cracking in the structural components of an airframe can occur during the service lifetimes of aging aircraft. These types of damage are…

Abstract

Purpose

Various types of damage or cracking in the structural components of an airframe can occur during the service lifetimes of aging aircraft. These types of damage are commonly repaired with a patch that can be joined to the original structure by different techniques, e.g., riveting and bonding. The purpose of this paper is to describe the repair of a fatigue crack in the metallic wing structure of a jet trainer aircraft using an adhesively bonded boron composite patch.

Design/methodology/approach

The partial analytical design and numerical analysis of the repair is presented. Three different versions of the patch are quantitatively investigated. The efficiency of the designed adhesively bonded boron patch with the parent metallic structure is experimentally verified by panel tests, and two different patch geometries and two surface preparation techniques are investigated. The panels were designed, manufactured and tested as representative structures of the repaired structure.

Findings

Adhesively bonded composite repair increases the lifetime by at least one order compared with the non-repaired structure. Both surface preparations provide equivalent results. The repair lifetime is significantly influenced by the patch geometry, and the longer patch significantly increases the lifetime of the panel. The lifetime of the structure can be increased by ˜40-fold if the patch geometry is a rectangle with 1:1.5 proportions of the sides (length in the crack direction/length perpendicular to the crack propagation). The patch length in the crack direction should be twice that of the initial crack length. Additional patch length extension in the direction that is perpendicular to the crack propagation does not appear to be effective for significantly decreasing the stress intensity factor and patch efficiency. The repair also retards the crack propagation if the crack grows out of the patch. No significant disbonding was detected.

Originality/value

The work described in this paper provides information that is very useful for patch design and verification with relation to different patch geometries and technologies. The designed and verified repair has been successfully applied to an L-39 Czech aircraft structure.

Details

International Journal of Structural Integrity, vol. 6 no. 2
Type: Research Article
ISSN: 1757-9864

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Article
Publication date: 13 April 2015

Roman Ružek, Konstantinos Tserpes and Evaggelos Karachalios

Impact and fatigue are critical loading conditions for composite aerostructures. Compression behavior after impact and fatigue is a weak point for composite fuselage…

Abstract

Purpose

Impact and fatigue are critical loading conditions for composite aerostructures. Compression behavior after impact and fatigue is a weak point for composite fuselage panels. The purpose of this paper is to characterize experimentally the compression behavior of carbon fiber reinforced plastic (CFRP) stiffened fuselage panels after impact and fatigue.

Design/methodology/approach

In total, three panels were manufactured and tested. The first panel was tested quasi-statically to measure the reference compression behavior. The second panel was subjected to impact so as to create barely visible impact damage (BVID) at different locations, then to fatigue and finally to quasi-static compression. Finally, the third panel was subjected to impact so as to create visible impact damage (VID) at different locations and then to quasi-static compression. The panels were tested using ultrasound inspection just after manufacturing to check material quality and between different tests to detect impact and fatigue damage accumulation. During tests the mechanical behavior of the panel was monitored using an optical displacement measurement system.

Findings

Experimental results show that the presence of impact damage significantly degrades the compression behavior of the panels. Moreover, the combined effect of BVID and fatigue was proven more severe than VID.

Originality/value

The paper gives information about the compression after impact and fatigue behavior of CFRP fuselage stiffened panels, which represent the most realistic loading scenario of composite aerostructures, and describes an integrated experimental procedure for obtaining such information.

Details

International Journal of Structural Integrity, vol. 6 no. 2
Type: Research Article
ISSN: 1757-9864

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Article
Publication date: 1 March 2005

Dennis Appo and Charmine E.J. Härtel

All Australian Aborigines have experienced the impact of Western culture to some extent which has resulted in the traditional cultures being irrevocably decimated. The…

Abstract

All Australian Aborigines have experienced the impact of Western culture to some extent which has resulted in the traditional cultures being irrevocably decimated. The reaction to the disintegration of traditional culture has been marked by a variety of outcomes. While some Aborigines have either accepted or reached a level of accommodation to the new order, others have responded in maladaptive ways. For some Aborigines, the disintegration of traditional culture and society has generated conflict, confusion and the disintegration of personality, which is conducive to the evolution of a dysfunctional group. It is the circumstances of and policy responses to dysfunctional Aboriginal groups, therefore, that is the concern of this article.

Details

Cross Cultural Management: An International Journal, vol. 12 no. 1
Type: Research Article
ISSN: 1352-7606

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Article
Publication date: 21 August 2017

Gustavo J. Nagy, Carolina Cabrera, Genaro Coronel, Marilyn Aparicio-Effen, Ivar Arana, Rafael Lairet and Alicia Villamizar

Climate change and variability are both a developmental and an environmental issue. Adaptation to climate change and variability has gained a prominent place on global and…

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Abstract

Purpose

Climate change and variability are both a developmental and an environmental issue. Adaptation to climate change and variability has gained a prominent place on global and local policy agendas, evolving from mainly climate risks impacts and vulnerability assessments to mainly adaptation action, imposing new defies to higher education (HE). The purpose of this paper is to introduce the Climate Vulnerability, Impact, and Adaptation (VIA) Network (CliVIA-Net), a South American university-based coalition aimed at achieving a science for/of adaptation.

Design/methodology/approach

CliVIA-Net is a collaborative effort by academic groups from across the spectrum of the natural, social and health sciences focused on improving climate VIA on education, research and practice. In consonance with international literature and practices, the network shifted from a discipline-oriented approach to an interdisciplinary and Earth System Science (ESS)-oriented one. It seeks to advance fundamental understanding and participatory practice-oriented research and to develop a problem orientation question/solving answering methodology. A set of cases studies illustrates how CliVIA-Net faces adaptation and sustainability challenges in the twenty-first century.

Findings

Focusing on interdisciplinary graduate education, practice-oriented research and problem orientation practice on climate threats which are already threatening the environment, population’s well-being and sustainability, allows for the co-production of knowledge and solutions, as well stakeholders’ buy-in and commitment.

Originality/value

CliVIA-Net draws upon the results of evolving interdisciplinary approaches on global change and VIA education, the research partnership with stakeholders and decision-makers to develop environmental and health outcomes, e.g. vulnerability indicators and scenario planning.

Details

International Journal of Climate Change Strategies and Management, vol. 9 no. 4
Type: Research Article
ISSN: 1756-8692

Keywords

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