다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

One of the most intriguing protein materials found in nature is bone, a material composed of assemblies of tropocollagen molecules and tiny hydroxyapatite mineral crystals that form an extremely tough, yet lightweight, adaptive and multifunctional material. Bone has evolved to provide structural support to organisms, and therefore its mechanical properties are of great physiological relevance. In this article, we review the structure and properties of bone, focusing on mechanical deformation and fracture behavior from the perspective of the multidimensional hierarchical nature of its structure. In fact, bone derives its resistance to fracture with a multitude of deformation and toughening mechanisms at many size scales ranging from the nanoscale structure of its protein molecules to the macroscopic physiological scale.

On the Mechanistic Origins of Toughness in Bone

Infrared thermography (IRT) applications for building diagnostics: A review

Active infrared thermography is a fast and accurate non-destructive evaluation technique that is of particular relevance to the aerospace industry for the inspection of aircraft and helicopters’ primary and secondary structures, aero-engine parts, spacecraft components and its subsystems. This review provides an exhaustive summary of most recent active thermographic methods used for aerospace applications according to their physical principle and thermal excitation sources. Besides traditional optically stimulated thermography, which uses external optical radiation such as flashes, heaters and laser systems, novel hybrid thermographic techniques are also investigated. These include ultrasonic stimulated thermography, which uses ultrasonic waves and the local damage resonance effect to enhance the reliability and sensitivity to micro-cracks, eddy current stimulated thermography, which uses cost-effective eddy current excitation to generate induction heating, and microwave thermography, which uses electromagnetic radiation at the microwave frequency bands to provide rapid detection of cracks and delamination. All these techniques are here analysed and numerous examples are provided for different damage scenarios and aerospace components in order to identify the strength and limitations of each thermographic technique. Moreover, alternative strategies to current external thermal excitation sources, here named as material-based thermography methods, are examined in this paper. These novel thermographic techniques rely on thermoresistive internal heating and offer a fast, low power, accurate and reliable assessment of damage in aerospace composites.

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Recent Advances in Active Infrared Thermography for Non-Destructive Testing of Aerospace Components.

Rotating detonation combustors and their similarities to rocket instabilities

Use of infrared thermography to investigate the fatigue behavior of a carbon fiber reinforced polymer composite

The aim of this study is to utilize infrared thermography to assess the critical damage states, and to capture the evolving damage processes, of 5HS and 8HS woven carbon fiber/epoxy composites subjected to uniaxial in-plane tensile quasi-static and fatigue loading. Quasi-static test results revealed that the dominant damage mechanisms were matrix cracks contained within the weft yarns, which initiated at the thermally-detected material thermoelastic limit and were confirmed through SEM observations. An established thermographic technique was also used to confirm the existence of a high cycle fatigue limit, which may in fact be a characteristic of all fabric reinforced polymeric composites. Temperature profiles captured during cyclic testing directly correlated with corresponding stiffness degradation profiles, providing support for thermography as an accurate fatigue damage metric. The infrared camera was able to detect the evolution of weft yarn cracking during the initial stage, as well as the initiation and growth of interply delamination cracking during the final stage of three-stage cyclic damage evolution. The reported results and observations provide an important step in the validation of thermography as a powerful non-destructive tool for assessing the development of damage, as well as predicting the critical damage states of fiber reinforced polymeric composite materials.

Non-destructive assessment of the fatigue strength and damage progression of satin woven fiber reinforced polymer matrix composites

The focus of this study is to assess, using infrared thermography, the fatigue behavior and the corresponding damage states of a textile polymeric composite plate, as a prerequisite step in the development of damage based life prediction models for such advanced composite materials. Monotonic (quasi-static) loading test results confirmed that the dominant damage mechanism is cracking in the braider yarns, which was monitored using thermographic images and confirmed by edge replication microscopic observations. Fatigue results confirmed that the saturation of braider yarn cracks during cyclic loading corresponded to changes in the stiffness degradation rate as well as the surface temperature profile. This was confirmed by edge replication and scanning electron microscopic analysis. The reported results and observations provide an important step in the validation of thermography as a powerful non-destructive evaluation tool for monitoring the development of fatigue damage as well as predicting the damage states of laminated composite materials in general, and braided polymeric composite materials in particular.

Application of infrared thermography for the characterization of damage in braided carbon fiber reinforced polymer matrix composites

Development of a physics-based multi-scale progressive damage model for assessing the durability of wind turbine blades

An energy-based model is developed to predict the evolution of sub-critical matrix crack density in symmetric multidirectional composite laminates for the case of multiaxial loading. A finite elementbased numerical scheme is also developed to evaluate the critical strain energy release rate, GIc, associated with matrix micro-cracking, a parameter that previously required fitting with experimental data. Furthermore, the prediction scheme is improved to account for the statistical variation of GIc within the material volume by using a two-parameter Weibull distribution. The variation of GIc with increasing crack density is also accounted for based on reported experimental evidence. The simulated results for carbon/epoxy and glass/epoxy cross-ply laminates demonstrate the ability of the improved model to predict the evolution of multidirectional ply cracking. By integrating this damage evolution model with the synergistic damage mechanics approach for stiffness degradation, the stress-strain response of the studied laminates is predicted. Finally, biaxial stress envelopes for ply crack initiation and predetermined stiffness degradation levels are predicted to serve as representative examples of stiffnessbased design and failure criterion.

John Montesano

Papers

Use of infrared thermography to investigate the fatigue behavior of a carbon fiber reinforced polymer composite

Non-destructive assessment of the fatigue strength and damage progression of satin woven fiber reinforced polymer matrix composites

Application of infrared thermography for the characterization of damage in braided carbon fiber reinforced polymer matrix composites

Development of a physics-based multi-scale progressive damage model for assessing the durability of wind turbine blades

Predicting evolution of ply cracks in composite laminates subjected to biaxial loading