Development of damage in some polymeric foam-core sandwich beams under bending loading

Ayorinde, Emmanuel O.; Ibrahim, R. A.; Berdichevsky, Victor L.; Jansons, Marcis; Grace, Ihab M.

doi:10.1177/1099636211433106

Cited by 9 publications

(6 citation statements)

References 11 publications

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“…In contrast, recently Ayorinde et al. [16] using acoustic emission (AE) and high-speed cameras claimed that the damage in their sandwich systems always started in the core, independant of the face sheets. Similar to Gibson, Ayorinde et al.…”

Section: Resultsmentioning

confidence: 98%

“…by Juntikka and Hallstrom [5] and Ayorinde et al. [16], this technique could be also interesting for online investigations of the shear strain in the core material, which is challenging to measure directly and accurately with conventional strain gauges. As mentioned in the experimental section, we only present a short part on the DIC measurements and a comprehensive analysis and discussion will be presented in a future manuscript.…”

Section: Resultsmentioning

confidence: 99%

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An investigation on the flexural properties of balsa and polymer foam core sandwich structures: Influence of core type and contour finishing options

Fathi

Wolff‐Fabris

Altstädt

et al. 2013

Jnl of Sandwich Structures & Materials

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Polymer foams are frequently used as core materials in sandwich structures for applications such as aerospace, naval, and wind industry. It is known that the core material contributes to the overall mechanical properties of these sandwich structures up to a remarkable extent. In addition, due to the curvature and geometrical complexities of several applications, these cores are available with special cuts/grooves (finishing options) to provide bendability and better resin infusion during processing. The goal of this study is to investigate the mechanical performance of synthetic polymer foams as core materials for sandwich structures. Balsa wood, which is the most common traditional structural core, was used as reference material. Glass fiber reinforced epoxy was employed as face sheets. End-grain Balsa wood, commercially available polyvinyl chloride and polyethylene terephthalate, and experimental grades of polyurethane foams were chosen as alternative core materials. Quasi-static flexural tests were carried out using a four-point bending setup according to ASTM C 393. Sandwich properties such as stiffness, core shear strength, and energy absorption were determined and compared. The contour cuts filled with resin show a reinforcing effect against transverse shear stresses leading to higher shear strengths. Digital image correlation was used to study the yielding and permanent strain of the foam core sandwich beams.

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Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

An investigation on the flexural properties of balsa and polymer foam core sandwich structures: Influence of core type and contour finishing options

Fathi

Wolff‐Fabris

Altstädt

et al. 2013

Jnl of Sandwich Structures & Materials

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“…It is believed that the damage in the impacted part may evolve in a different way from that occurring in the tests adopted to determine the damage curve for the model, which is measured under tensile loading. The damage mechanism in sandwich plates with polymer foam cores has been investigated in the literature [ 29 , 30 ], showing the importance of shear stresses developing in the core under bending loads. Similarly, it is recognized that stress triaxiality is relevant in the void growth in damaged materials during the “void coalescence phase”, which anticipates material failure [ 31 ].…”

Section: Discussionmentioning

confidence: 99%

An Approach to the Impact Simulation on Foamed Injection Molded Polypropylene Parts: An Example of Application in the Automotive Industry

2023

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An approach to the simulation of foamed injection molded Polypropylene parts subjected to impact loading is presented in this paper. The proposed method, which considers strain-rate-dependent material properties and the possible occurrence of fracture, is, in particular, suitable for parts manufactured with core-back technology. The method was developed to be used within the functionality of a commercial Finite Element solver using a shell-type element mesh. The material model is based on a three-layer structure, with two compact skin layers and a foamed core layer made of expanded material. The properties of the foamed material are assumed as those of the compact grade scaled by a suitable factor, which is identified via inverse engineering on a set of bending tests executed on specimens having different foam densities. The fracture of the material is then predicted using a damage model which considers the effects of triaxiality. The approach is then validated on industrial parts from the automotive sector, subjected to impact in a component test. Despite the simplicity of the presented approach, which makes this method suitable for industrial applications and especially for early-stage design, the validation shows a sufficiently accurate simulation of part behavior under the impact, with a reasonable prediction of damage and fracture.

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“…The cracks propagate so fast that it is hard to detect the place where the crack was nucleated, in the core or in the skin-bonding area. The damage mechanisms in sandwich plates with polymer foam cores were investigated by Ayorinde et al (2012) using four-point bending tests of a sandwich plate monitored by a high-speed camera. It was found that in all cases, cracks are nucleated inside the polymer foam core.…”

Section: Damage Of Composite Structuresmentioning

confidence: 99%

Overview of Structural Life Assessment and Reliability, Part I: Basic Ingredients of Fracture Mechanics

Ibrahim¹

2015

j ship prod des

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Structural life assessment periodically evaluates the state and condition of a structural system and provides recommendations for possible maintenance actions or the end of structural service life. It is a diversified field and relies on the theories of fracture mechanics, fatigue damage process, probability of failure, and reliability. With reference to naval ship structures, their life assessment is not only governed by the theory of fracture mechanics and fatigue damage process, but by other factors such as corrosion, grounding, and sudden collision. The purpose of this series of review articles is to provide different issues pertaining to structural life assessment of ships and ocean structures. Part I deals with the basic ingredients of the theory of fracture mechanics, which is classified into linear elastic fracture mechanics and elasto-plastic fracture mechanics. The amount of energy available for fracture is usually governed by the stress field around the crack, which is measured by the stress intensity factor. The value of the stress intensity factor, which depends on the loading mode, is evaluated by different methods developed by many researchers. The applications of the theory of fracture mechanics to metallic and composite structures are presented with an emphasis to those used in marine structures. When the inertia of relatively large pieces of a structure is large enough that the correct balancing of the energy of fracture requires the inclusion of kinetic energy, then the dynamic nature of fracture dominates the analysis. For a crack that is already propagating, the inertial effects are important when the crack tip speed is small compared with the stress wave velocities. This fact has been realized in the theory of fracture mechanics under the name of dynamic fracture and peridynamic. In essence, peridynamic replaces the partial differential equations of classic continuum theories with integro-differential equations as a tool to avoid singularities arising from the fact that partial derivatives do not exist on crack surfaces and other singularities. A brief overview of fracture dynamics and peridynamics together with damage mechanisms in composite structures is presented. The limitations of fracture mechanics criteria are also discussed. Life assessment of ship structures depends on the failure modes and the probabilistic description of failure, which are addressed in Part II. Life assessment of ship structures depends on the failure modes and the probabilistic description of failure. In view of structural parameter uncertainties, probabilistic analysis requires the use of reliability methods for assessing fatigue life by considering the crack propagation process and the first passage problem, which measures the probability of the exit time from a safe operating regime. The main results reported in the literature pertaining to ship structural damage assessments resulting from to slamming loads, liquid sloshing impact loads of liquefied natural gas in ship tankers, and ship grounding accidents, an...

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Development of damage in some polymeric foam-core sandwich beams under bending loading

Cited by 9 publications

References 11 publications

An investigation on the flexural properties of balsa and polymer foam core sandwich structures: Influence of core type and contour finishing options

An investigation on the flexural properties of balsa and polymer foam core sandwich structures: Influence of core type and contour finishing options

An Approach to the Impact Simulation on Foamed Injection Molded Polypropylene Parts: An Example of Application in the Automotive Industry

Overview of Structural Life Assessment and Reliability, Part I: Basic Ingredients of Fracture Mechanics

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