The Detection of Damage and the Measurement of Strain within Composites by Means of Embedded Optical Fiber Sensors

Structurally integrated fiber optic sensors hold the promise of improved quality control of composites and “real-time, in-service” monitoring of the loads to which they are subjected and any damage they may sustain. This could reduce overdesign and increase confidence in their use by improving both safety and their economics especially in terms of inspection and maintenance, Figure 1. This would be particularly relevant to the Aerospace Industry where any weight saving has a multiplier effect. The technology of imbedding arrays of optical fiber sensors within advanced composite material structures during their fabrication essentially provides materials with “optical nerves”. Improved quality control would be achieved by monitoring the internal of composites during their manufacture. Also since “in-service” monitoring of structural loads and structural integrity would permit weaknesses to be indicated before they became critical, longer periods could be allowed between costly inspections. When the system is taken out of service for such an inspection, a shorter downtime might be expected since the built-in sensors would have already indicated sites of weakness and their rate of deterioration. A recent overview of fiber optic based “Smart Structures” has been prepared by the author[1]

Bragg Grating Corrosion Sensor

Historically, corrosion has not been included in the calculation of the life expectancy of aircraft. It is well known how stress-corrosion cracking and corrosion fatigue can significantly reduce the life expectancy of structures. Therefore, it can be correctly assumed that some aircraft flying near their expected life might actually be flying well beyond their “safe life”. Furthermore, due to DoD present tight budget requirements, its is expected that some defense aircraft might not be retired at their original expected life but will be reconditioned to fly beyond that time. All of these considerations indicate that early detection, quantification and prevention of corrosion is of critical importance for military aircraft. This is particularly true for Navy aircraft which fly in the most corrosive environment of all services

Stabilized Fiber Optic Sensor for Ultrasound Detection

Fiber optic sensors are emerging as important new tools in the field of nondestructive evaluation (NDE). They offer a number of advantages over sensing elements traditionally used in NDE applications such as resistive foil strain gauges and piezoelectric transducers. The advantages of fiber optic sensors over traditional NDE sensors include: ease of embedding in composite materials, good mechanical interaction between the embedded sensor and the host structure, insensitivity to electrical interference, and fine spatial resolution [1]. Additionally, fiber optic sensors can be configured to detect a variety of fields from large slowly varying thermal and mechanical strains, to ultrasound and acoustic emission. They have shown potential in a variety of material systems such as graphite/epoxy composites [2], titanium matrix composites [3], aluminum [4], and concrete [5]. They have also been embedded in a number of practical structures including airplanes [6][7], buildings [8][9], and dams [10].</p

Cerebral Bypass Surgery: Level of Evidence and Grade of Recommendation

BACKGROUND AND AIMS Cerebral bypasses are categorized according to function (flow augmentation or flow preservation) and to characteristics: direct, indirect or combined bypass, extra-to-intracranial or intra-to-intracranial bypass, and high-, moderate- or low-capacity bypass. We critically summarize the current state of evidence and grades of recommendation for cerebral bypass surgery. METHODS The current indications for cerebral bypass are discussed depending on the function of the bypass (flow preservation or augmentation) and analyzed according to level of evidence criteria. RESULTS Flow-preservation bypass plays an important role in managing complex intracranial aneurysms (level of evidence 4; grade of recommendation C). Flow-preservation bypass is currently only very rarely indicated in the treatment of cerebral tumors involving major cerebral arteries (level of evidence 5; grade of recommendation D). The trend has evolved in favor of partial resection and radiotherapy. To preserve the flow, the bypass is always a direct bypass.Flow-augmentation bypass is currently recommended for Moyamoya patients with ischemic symptoms and compromised hemodynamics (level of evidence 4; grade of recommendation C) and patients with hemorrhagic onset (level of evidence 1B; grade of recommendation A). Flow-augmentation bypass is currently not recommended for patients with recently symptomatic carotid artery occlusion, even in the setting of compromised cerebral hemodynamics (level of evidence 1A; grade of recommendation A), but may be considered in patients with hemodynamic failure and recurrent medically refractory symptoms as a final resort (level of evidence 5; grade of recommendation D). CONCLUSIONS The results of recent randomized clinical trials narrow the indication for cerebral bypass in the setting of ischemic cerebrovascular disease. However, cerebral bypass is still very useful for managing complex intracranial aneurysms (not amenable to selective clipping or endovascular therapies) and is the only treatment option for managing symptomatic patients with Moyamoya vasculopathy and impaired brain hemodynamics

International Consensus Statement on Rhinology and Allergy: Rhinosinusitis

Background: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICAR‐RS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICAR‐RS‐2021 as well as updates to the original 140 topics. This executive summary consolidates the evidence‐based findings of the document. Methods: ICAR‐RS presents over 180 topics in the forms of evidence‐based reviews with recommendations (EBRRs), evidence‐based reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary. Results: ICAR‐RS‐2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidence‐based management algorithm is provided. Conclusion: This ICAR‐RS‐2021 executive summary provides a compilation of the evidence‐based recommendations for medical and surgical treatment of the most common forms of RS

Growth of Damage Within Composites Determined by Image Enhanced Backlighting and Embedded Optical Fibers

The aerospace industry is increasing its use of composite materials because of their: high strength and stiffness to weight ratio, low thermal expansion and resistance to fatigue and corrosion. Furthermore, their elastic and thermal properties can be tailored to suit anticipated service loads. Unfortunately, the very nature of these fibre reinforced polymers makes them prone to several types of damage. Among these damage modes, interlamina disbonding, or delamination, has been found to be the most serious. This form of damage can be induced by relatively low energy impacts such as a carelessly dropped tool, runway stones, hail and once started the region of damage can grow with the load cycling incurred in normal operation