1,721,017 research outputs found
A numerical procedure for the simulation of skin–stringer debonding growth in stiffened composite panels
No full textIn this paper, a numerical study on the skin-stringer debonding growth in composite panels under compressive load is presented. A novel numerical procedure, for the selection of proper material parameters governing the traction-separation law in Cohesive Zone Model (CZM) based elements, is introduced and demonstrated. Indeed, the proposed procedure uses Virtual Crack Closure Technique (VCCT) based FEM analyses on Double Cantilever Beam (DCB) and End Notched Flexure (ENF) specimen to characterize the traction-separation law, respectively, for fracture mode I and mode II. The established traction-separation laws are then applied to composite structures containing inter-laminar damages modeled by cohesive elements. To validate the proposed approach, a single stringer panel under compression with an artificial debonding between skin and stringer, has been considered. The numerical results, in terms of displacements and debonding size as a function of applied compressive load, have been compared to experimental data available in literature providing a good numerical-experimental correlation
A Practical Tool for The Preliminary Design of Bonded Composite Repairs
No full textComposite structures are increasingly finding more applications in the aeronautical field as well as the automotive one, thanks to their low weight – performance ratios, in terms of strength and stiffness. However, composite materials, as well known, are characterized by a critical behavior in terms of detectability of damage and performances of damaged components. A critical aspect related to damaged composite structures is, for sure, the repair aimed to restore the original stiffness and strength characteristics of the component depending on the damage typology and location.
In this paper, a preliminary repair design tool is presented. The tool is aimed to help the designer by suggesting different repair typologies and proper repair size. This tool, by means of optimization analyses can provide the best repair solution with minimal adhesive shear stress and size of the repair patch. The tool has been tested against a literature case study on multistep composite-metal joints
The vulnerability of places in the Covid-19 pandemic. An analysis model based on spatial interaction|La vulnerabilità dei luoghi nella pandemia da Covid-19. Un modello di analisi basato sull’interazione spaziale
No full textA numerical procedure for the simulation of skin-stringer debonding growth in stiffened composite panels
No full textIn this paper, a numerical study on the skin–stringer debonding growth in composite panels under compressive load is presented. A novel numerical procedure, for the selection of proper material parameters governing the traction–separation law in Cohesive Zone Model (CZM) based elements, is introduced and demonstrated. Indeed, the proposed procedure uses Virtual Crack Closure Technique (VCCT) based FEM analyses on Double Cantilever Beam (DCB) and End Notched Flexure (ENF) specimen to characterize the traction–separation law, respectively, for fracture mode I and mode II. The established traction–separation laws are then applied to composite structures containing inter-laminar damages modeled by cohesive elements. To validate the proposed approach, a single stringer panel under compression with an artificial debonding between skin and stringer, has been considered. The numerical results, in terms of displacements and debonding size as a function of applied compressive load, have been compared to experimental data available in literature providing a good numerical–experimental correlation
A NUMERICAL STUDY ON LOW VELOCITY IMPACT INDUCED DAMAGE IN STIFFENED COMPOSITE PANELS
No full textImpact induced damage is ofter of main concern for aeronautic structures. The aircraft can undergo low velocity impacts during the assembly stage and during its operative life. Delamination and other damage mechanisms, such as matrix cracks, fibre-matrix debonding and fiber breakages can be the consequence of impact events with foreign objects under in service conditions and maintenance operations. Dam-ages induced by low velocity impacts can be hardly detected by visual inspections because they often are confined deeply in the laminate thickness. Hence the use of expensive and time consuming non-destructive techniques such as ultrasonic tests, can be required. In order to prevent catastrophic events, as a consequence of impacts, designers usually increase the structural safety margins thereby increasing the weight of the aircraft. In the frame of the present work, in order to quantify the influence of impact events on the load carrying capability of complex composite structures, specific advanced numerical techniques are used to take into account the skin-stringer debonding phenomena arising in stiffened composite panels as a consequence of low velocity impact events
STACKING SEQUENCE EFFECTS ON DAMAGE ONSET IN COMPOSITE LAMINATE SUBJECTED TO LOW VELOCITY IMPACT
No full textIn this paper, the effects of the stacking sequence on the mechanical behavior of composite laminates subjected to low velocity
impacts is investigated, taking into account inter-laminar and intra-laminar damage onset and evolution. The response of the
composite laminate configurations characterized by different stacking sequences subjected to low velocity impacts with different
impact energies have been studied to estimate the influence on the load-time, displacement-time and energy-time histories. A
Finite element (FE) model has been used to numerically simulate the behavior of the composite plates. ABAQUS/EXPLICT FE
environment has been considered for the implementation and the analyses and cohesive elements have been adopted to model the
inter-laminar damage formation and evolution in the analyzed composite plate
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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