Damage evolution in flexible polyurethane foams

Kau, C.; Huber, L.; Hiltner, A.; Baer, E.

doi:10.1002/app.1992.070441202

Cited by 9 publications

(3 citation statements)

References 25 publications

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“…The fracture was found to increase rapidly with crack length. Microcrazing in the struts of flexible PU foams was observed during compressive deformation and observed directly in the scanning electron microscope [7]. Attributed to this phenomenon was the decrease in stress at maximum compression and the intensity of AE during compressive cycling.…”

Section: Introductionmentioning

confidence: 99%

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

Ayorinde

Ibrahim

Berdichevsky

et al. 2012

Jnl of Sandwich Structures & Materials

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The damage mechanisms in sandwich plates with polymer foam cores are investigated. There has been a long-standing controversy on what is the weakest element of sandwich plates, the skin-core bonding or the foam core. Under four-point bending of a sandwich plate, we found that in all cases cracks are nucleated inside the polymer foam core as monitored by a high-speed camera. Several separated small cracks develop in the core; then the small cracks are connected and form the main crack that propagates through the core. We complemented the optical recording by the acoustic emission study which provides an additional insight in the fracture process. In addition, the influence of sub-zero temperature of the ultimate load of each material is examined at discrete values of sub-zero temperature. The results revealed that both materials become increasingly brittle with decreasing temperature.

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Section: Introductionmentioning

confidence: 99%

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

Ayorinde

Ibrahim

Berdichevsky

et al. 2012

Jnl of Sandwich Structures & Materials

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“…The fracture was found to increase rapidly with crack length. Microcrazing 7 in the struts of flexible polyurethane foams was observed during compressive deformation and observed directly in the scanning electron microscope (Kau et al 1992). Attributed to this phenomenon was the decrease in stress at maximum compression and the intensity of acoustic emission during compressive cycling.…”

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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“…This repetitive cycle accumulates stress in the sealant body, and this results in the degradation of sealant properties. 2) Water molecules affect the hydrogen bond in the hard phase of the polyurethane, which causes irreversible damage to the sealant (Kau et al, 2010). Various microcosmic examination methods were also introduced to characterize the micro-properties of sealants.…”

Section: Introductionmentioning

confidence: 99%

Adhesive Characteristic and Mechanism of Ballastless Track Sealant in Hydrolysis Condition

2020

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The current evaluation method cannot predict accurately the hydrolysis resistance of sealants applied in ballastless slab track. And the degradation mechanism of sealant in hydrolysis condition has not been researched systemically. In this paper, the hydrolysis resistance of different sealants was researched with the aid of the self-developed direct tensile test method. The atomic force microscope was employed to analyze the microadhesion force on the surface of sealants, and thereby the correlation between macrobehavior and the micro-mechanism of sealants during hydrolysis was established. Results showed that the characteristics of the interface between sealants and substrates are reduced after hydrolysis, and that sealants with higher soft-segment content have good resistance to hydrolysis. Reduction of the bonding area after hydrolysis is also an important factor in the reduction of the characteristics of the adhesive interface. The micro-adhesion force of soft segments shows a fluctuating reduction tendency, and that of hard segments reduces more significantly during hydrolysis. The micro-adhesion force has good correlation with the maximum tensile force, but a poor correlation with failure displacement. The maximum tensile force is proved to be an optimal evaluation index in determining the hydrolysis resistance of sealants.

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Damage evolution in flexible polyurethane foams

Cited by 9 publications

References 25 publications

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

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

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

Adhesive Characteristic and Mechanism of Ballastless Track Sealant in Hydrolysis Condition

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