Experimental investigation of interfacial crack arrest in sandwich beams subjected to fatigue loading using a novel crack arresting device

A recently proposed face-sheet/core interface crack arresting device is implemented in sandwich beams and tested using the Sandwich Tear Test (STT) configuration. Fatigue loading conditions are applied to propagate the crack and determine the effect of the crack stopper on the fatigue growth rate and arrest of the crack. Digital image correlation is used through the duration of the fatigue experiment to track the strain evolution as the crack tip advances. The measured strains are related to crack tip propagation, arrest, and re-initiation of the crack. A finite element model is used to calculate the energy release rate, mode mixity and to simulate crack propagation and arrest of the crack. Finally the effectiveness of the crack arresting device is demonstrated on composite sandwich beams subjected to fatigue loading conditions

Experimental investigation of interfacial crack arrest in sandwich beams subjected to fatigue loading using a novel crack arresting device

A recently proposed face-sheet–core interface crack arresting device is implemented in sandwich beams and tested using the Sandwich Tear Test configuration. Fatigue loading conditions are applied to propagate the crack and determine the effect of the crack stopper on the fatigue growth rate and arrest of the crack. Digital image correlation is used through the duration of the fatigue experiment to track the strain evolution as the crack tip advances. The measured strains are related to crack tip propagation, arrest, and re-initiation of the crack. A finite element model is used to calculate the energy release rate, mode mixity and to simulate crack propagation and arrest of the crack. Finally, the effectiveness of the crack arresting device is demonstrated on composite sandwich beams subjected to fatigue loading conditions

Interfacial crack arrest in sandwich beams subjected to fatigue loading using a novel crack arresting device - Numerical modelling

A novel crack arresting device is implemented in foam cored composite sandwich beams and tested using the Sandwich Tear Test (STT) configuration. A Finite Element Model of the setup is developed, and the predictions are correlated with observations and results from a recently conducted experimental fatigue test study. Based on a linear elastic fracture mechanics approach, the developed FE model is utilized to simulate crack propagation and arrest in foam cored sandwich beam specimens subjected to fatigue loading conditions. The effect of the crack arresters on the fatigue life is analysed, and the predictive results are subsequently compared with the observations from the previously conducted fatigue tests. The FE model predicts the energy release rate and the mode mixity based on the derived crack surface displacements, utilizing algorithms for the prediction of accelerated fatigue crack growth as well as the strain field evolution in the vicinity of the crack tip on the surface of the sandwich specimens. It is further shown that the developed finite element analysis methodology can be used to gain a deeper insight onto the physics and behavioral characteristics of the novel peel stopper concept, as well as a design tool that can be used for the implementation of crack arresting devises in engineering applications of sandwich components and structures

Integrating heterogeneous communication and messaging systems in an object-oriented middleware framework

Integrated communications have been largely associated with message-oriented middleware in collaborative distributed computing environments, both on small and large scales. Past experience has shown that monolithic architectures based on large executables are extremely difficult to maintain and very unresponsive to change. This paper aims at proposing an intelligent, object-oriented communications and messaging architecture based on interrelated business objects and components, designed to support business-to-business communication. The philosophy behind our approach has been to construct a scalable and flexible system architecture that enables the incorporation of new services at minimum effort. The framework allows for the implementation of reusable components, independently from the core architecture, that can be automatically discovered, configured and plugged-in to the system and used as.cartridges. on demand, according to the communication requirements of the application that will make use of the bearers linked to the system. © Springer-Verlag Berlin Heidelberg 200

Fracture behaviour at tri-material junctions of crack stoppers in sandwich structures

Inspired by a previously published peel stopper design for foam cored composite sandwich structures, three novel markedly lighter peel stoppers were evaluated with respect to their ability to deflect and arrest propagating face debond cracks. Of the three novel peel stopper configurations, C1, C2 and C3, C1 was similar to the previous design, whereas C2 and C3 were modified with layers of glass fibre fabric extending from the peel stopper tip into the face sheet (C2) or into the face sheet/core interface (C3). The previous peel stopper was validated under mode II dominated conditions, but the novel designs were investigated under mode I dominated crack propagation conditions, which are of higher practical relevance. Both quasi-static and fatigue loading scenarios were investigated. The mechanisms controlling crack propagation at the internal peel stopper tip were studied using Thermoelastic Stress analysis (TSA) and Finite Element (FE) analysis. The TSA has revealed significant new information about the local stress fields in the vicinity of the tri-material junction (peel stopper tip) as well as the fracture process zone. Configuration C1 was unable to deflect debond cracks consistently, albeit it did so in most cases, whereas it was incapable of achieving crack arrest. C2 and C3 both performed better in that they consistently demonstrated the ability to deflect propagating cracks, whereas only C2 could arrest the cracks consistently as well. Detailed fracture mechanics analyses confirmed and explained the experimental observations