101,946 research outputs found
Ultrasonic technique for the evaluation of delaminations on CFRP, GFRP, KFRP composite materials
No full textIn the present paper an ultrasonic NDI technique for the delaminations evaluation on several composite materials is described. The methodology, based on an ultrasonic test apparatus in the form of reflection, allows us to determine the position along the thickness and extension of delaminations on several CFRP, GFRP and KFRP laminates subjected to low-velocity impact test. The experiments have been performed in two distinct phases. During the first phase typical aerospace materials such as thermoset and thermoplastic CFRP thin laminates and sandwich were inspected, in order to validate the ultrasonic NDI system and the original test methodology. Then, in the second phase, tests have been performed on glass fiber and polyester resin systems, where the fiber was in the form of woven fabric or woven roving, and Kevlar and polyester resin system, where the Kevlar is in the form of woven fabric. All the specimens are made by RTM technology and the thickness are comprised between 5 and 6 mm. Moreover, the NDI analysis was performed using two different probes (5 and 15 MHz), in order to evaluate the importance of the probe frequency for the reliable evaluation of delaminations on composite materials. The results show the NDI system capabilities in terms of damage detection, location and evaluation. (C) 2000 Elsevier Science Ltd. All rights reserved
Acoustic Attenuation for Ultrasonic NDI Detection of Delaminations on Composite Laminates
No full textMatch Analysis and Temporal Patterns of Fatigue in Rugby Sevens
No full textGranatelli, G, Gabbett, TJ, Briotti, G, Padulo, J, Buglione, A,
D'Ottavio, S, and Ruscello, BM. Match analysis and temporal patterns of
fatigue in rugby sevens. J Strength Cond Res 28(3): 728-734, 2014-Rugby
sevens is a rapidly growing sport. Match analysis is increasingly being
used by sport scientists and coaches to improve the understanding of the
physical demands of this sport. This study investigated the physical and
physiological demands of elite men's rugby sevens, with special
reference to the temporal patterns of fatigue during match play. Nine
players, 4 backs and 5 forwards (age 25.1 +/- 3.1 years) participated
during 2 ``Roma 7(s){'' international tournaments (2010 and 2011). All
the players were at the professional level in the highest Italian rugby
union, and 5 of these players also competed at the international level.
During the matches (n = 15), the players were filmed to assess game
performance. Global positioning system, heart rate (HR), and blood
lactate (BLa) concentration data were measured and analyzed. The mean
total distance covered throughout matches was 1,221 +/- 118 m (first
half = 643 +/- 70 m and second half = 578 +/- 77 m; with a decrease of
11.2\%, p > 0.05, Effect Size [ES] = 0.29). The players achieved 88.3
+/- 4.2 and 87.7 +/- 3.4\% of the HRmax during the first and second
halves, respectively. The BLa for the first and second halves was 3.9
+/- 0.9 and 11.2 +/- 1.4 mmol center dot L-1, respectively. The
decreases in performance occurred consistently in the final 3 minutes of
the matches (-40.5\% in the distance covered per minute). The difference
found in relation to the playing position, although not statistically
significant (p = 0.11), showed a large ES (eta(2) = 0.20), suggesting
possible practical implications. These results demonstrate that rugby
sevens is a demanding sport that places stress on both the anaerobic
glycolytic and aerobic oxidative energy systems. Strength and
conditioning programs designed to train these energy pathways may
prevent fatigue-induced reductions in physical performance.
Ultrasonic Techniques for the Evaluation of Delaminations on CFRP, KFRP and GFRP Composite Laminates
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POSSIBILITA' DIAGNOSTICHE E LIMITI DELLA TERMOGRAFIA NELLO STUDIO DELLE VIE LACRIMALI DI DEFLUSSO
No full textAfter reviewing the possibilities of the radiological (Dacryography, scintiliography) and para-radiological (ultrasonography, thermography) studies useful for the diagnosis of desorders of the lacrimal pathways, the Authors pay particular attention to the actutal possibilities of thermography.
This examination allows evaluating the anatomy and patency of the lacrimal drainage system and also provides to diagnose sub-clinical inflammations. In the lacrimal area thermography may also help to establish improved guide lines for surgical intervention.
Concluding the Authors think that thermography offers promise as a safe, simple and efficient clinical tool having however a relevant limitation compared with the other lacrimal diagnostic techniques (Dacryograpy, scintillography, echography)
Impact Testing on Composite Laminates and Sandwich Panels
No full textThe purpose of this work was the evaluation of the behavior of fiber-reinforced composites and sandwich panels for aeronautical applications under impact.
Experimental tests were performed on several specimen configurations, based on different quasi-isotropic lay-up and materials such CFRP, CFRTP and a syntactic foam as the core of sandwich panels. Considering the high specific mechanics characteristics of such a foam and its cocurability with the facesheet material, symmetric and non-symmetric sandwich configurations have been tested. The study has pointed out the advantages for aeronautic constructions of different materials and the influence of the core position along the panel thickness.
The impact tests were performed with a falling weight machine, which allowed the most important dynamic and kinetic parameters, such as the contact force, impactor velocity and displacement and perforation energy to be measured. Delamination areas of each specimen were also measured using N.D.I. reflection ultrasonic techniques. In order to determine the residual strength, Compression After Impact tests were performed on specimens that have an indentation of approximately 0.3-0.4 mm.
A numerical simulation was performed using a transient dynamic Finite Element Analysis. The main goal of this analysis was to define the controlling factors for high velocity impact simulation, such as the increase of geometric non-linearity and the delamination effects. Moreover, the delamination areas and positions were determined taking in account the different boundary conditions.
The study have pointed out the behavior of thermoset, thermoplastic and unsymmetric sandwich panels
Influence of material thickness on the response of graphite fabric/epoxy panels to low velocity impact
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