In this international permeability benchmark exercise, in-plane permeability data for two reinforcement fabrics, obtained using a total of 16 different experimental procedures, were compared. ...Although, for each procedure, the results appear consistent, different procedures result in a scatter of up to one order of magnitude in principal permeability values for each fabric at any given fibre volume fraction. The ratio of the principal permeability values varies by factors of up to 2. While experimental uncertainties and variability of the specimens affect the scatter in results for any single series of experiments, it is suspected that the main source of scatter in results from different procedures is related to human factors. Aiming at standardisation of measurement methods and interchangeability of results, “good practice” guidelines will be formulated in order to eliminate sources of scatter.
We report Second Harmonic Generation (SHG) and Third Harmonic Generation (THG) energy conversion efficiencies up to 59% and 27%, respectively, for laser pulses simultaneously delivering high peak ...power in the sub-TW range and average powers in the sub-kW range. No damage or efficiency decrease is observed after more than 100 h operation time. The resulting high-energy visible and near-UV pulses are suitable for applications, such as lightning control, material analysis and machining, or OPCPA pumping.
Nowadays, the market demand for environmentally friendly materials is rapidly increasing. Biodegradable fibers and biodegradable polymers, mainly extracted from renewable resources, are expected to ...be a major contribution to the production of new industrial high performance biodegradable composites, partially solving the problem of waste management. At the end of its lifetime, a structural biodegradable composite can be crushed and recycled through a controlled industrial composting process. Bodros et al. 1 showed that biodegradable L-polylactide acid (PLLA)/flax fibers mat composites exhibiting specific tensile properties equivalent to glass fiber polyester composites can be manufactured by an un-optimized film-stacking process. In our study, the process has been investigated more extensively. Indeed, the compaction of flax mats requires a higher load than for glass mats of similar areal weight. The transverse permeability of flax mats has also been shown to be lower than for glass mats. In both cases, this is due to a higher degree of entanglement of the flax fibers within the mat. However, the range of permeability and compressibility values of the flax mats are well within the values that allow a good through-the-thickness impregnation. Flax fibers cannot sustain long exposures at the impregnation temperature of the mats by PLLA resin. Through-the-thickness impregnation of flax mats processes such as film stacking are more suitable than in-plane impregnation processes such as resin transfer molding because the flow of resin is limited on short distances and allows short times of impregnation.
We propose a comparative study of X-ray tomography and ultrasonic reflection methods, for determining the porosity of a composite plate realized in LOMC with an industrial process. We measure the ...attenuation of ultrasound propagating in the thickness by using 10MHz plane transducer in pulse-echo mode. Comparing these results to the 2D porosity tomographic map allows establishing a relation between attenuation and porosity. A C-scan picture of the plate given by the echoes reflected by the rear surface also provides a local information on the attenuation. Furthermore, we propose a method for the mapping of the reflecting sources as the included bubbles and the interfaces resin/fibers.
Laser-Guided Lightning Using kHz Filamentation at 1030 nm Houard, A.; Walch, P.; Produit, T. ...
2023 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC),
2023-June-26
Conference Proceeding
Controlling lightning is a long-time dream of mankind. Along with the rapid evolution of laser technologies, the idea to develop lightning protection based on filamentation of high-power ...ultrashort-pulse lasers emerged in the 1990s 1. The goal of the Laser Lightning Rod (LLR) project that started in 2017 was to investigate a new type of lightning protection based on the use of upward lightning discharges initiated through a high-repetition-rate terawatt laser 2. To that end, a high-power laser was developed by Trumpf scientific with pulse energy in the Joule-range, 1 ps pulse duration, and a repetition rate of 1 kHz 3. This CPA laser system is based on Yb-YAG thin-disk technology allowing amplification at very high average power at a wavelength of 1030 nm.
The present study was designed in order to analyze our experience in surgical treatment of 18 patients with abdominal aortic aneurysm associate to a high surgical risk from 1982 (January-February) to ...1988, both included. Selection criteria and surgical technical aspects were established. The patient age ranged from 60 to 82, with an average age of 75 +/- 7.5 years. The most frequently associated pathology was hypertension disease, followed by cerebrovascular disease and ischemic cardiopathy. Two patients died during surgical procedure. Fifteen patients, from the 16 surviving, suffered a complete thrombosis of their aneurysmatic sac one week after the induced thrombosis, by the ligature of afferent arteries of their aneurysm (iliac arteries). Only one patient suffered a second operation, 4 months after the initial procedure (partial exclusion) during which a total exclusion of aneurysm by infrarenal aortic ligature was performed. The successful operatory rate was of 14/15 (93.3%), with a mortality rate of 2/18 (11.1%). References are reviewed and our results commented.
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