Flexible thin polymer waveguide Bragg grating sensor foils for strain sensing

This paper demonstrates that epoxy-based single mode polymer waveguides with Bragg gratings can be realized in very thin (down to 50 micron) polymer foils which are suitable for strain sensing when integrated inside glass fiber reinforced polymer composite materials. The single mode waveguides were fabricated using laser direct-write lithography and the gratings were realized using nanoimprint lithography. These steps were performed on a temporary rigid carrier substrate and afterwards the functional layers were released yielding the thin, flexible sensor foils which can be laser-cut to the required dimensions. The Bragg grating-based polymer waveguide sensor foils were characterized before and after embedding into the composite. As expected, there was a blue shift in the reflection spectrum because of residual strain due to the embedding process. However, the quality of the signal did not degrade after embedding, both for 50 and 100 micron thick sensor foils. Finally, the sensitivity to strain of the embedded sensors was determined using a tensile test and found to be about 1 pm / microstrain

Zajednice hrasta oštrika (Quercus coccifera s. l.) na obalama u području Otranta (Lecce — južni dio Puglie — Italija)

The Authors present the description of a spiny oak (Quercus coccifera s. 1.) station near Otranto and propose a phytosociological interpretation connected to the local vegetational dynamism. The coenosis is part of the degradation series of Quercion ilicis leading to Oleo-Ceratonion of secondary origin.Fitocenološko istraživanje pojedinih zajednica hrasta oštrika (Quercus coccifera) uz obalu otrantskog područja (južni dio Puglie) potvrdilo je ono što je već prije primijećeno u drugim područjima Puglie s obzirom na njihovu fitocenološku pripadnost. Snimljene sastojine pokazuju, zapravo, jasnu tendenciju razvitka prema svezi Quercion ilicis više nego prema svezi Oleo-Ceratonion; ono isto što se događa u sjeverozapadnim područjima areala hrasta oštrika. Smatra se, na temelju dinamičnosti vegetacije, da je to područje vrlo blisko ass. Cocciferetum Br.-Bl. 1924; čak mnogi degradacijski aspekti slijede »provansalsku« shemu s osobitom pojavom vrste Brachypodium izražene u subass. brachypodietosum Br.-Bl. 1951. unutar as. Quercatum ilicis galloprovinciale

Deformable microsystem for in situ cure degree monitoring of GFRP(Glass Fibre Reinforced Plastic)

Fibre Reinforced Polymer (FRP) is becoming a valid alternative to many traditional heavy metal industries because of its high specific stiffness over the more classical construction metals. Recent trend of more complex geometry of composites is causing increasing difficulty in composite manufacturing. A method to optimize the manufacturing process is thus imposed to ensure and improve the quality of manufactured parts. Because of the irregular 3D shapes of the composites, traditional flat sensor system is becoming unfavorable and nonpractical for monitoring purpose. In this work, the current development status of a deformable microsystem for in situ cure degree monitoring of a glass fibre reinforced plastic is presented. To accommodate the non-flat shape of the composites, the proposal is to interconnect non-deformable functional island, which contains the capacitive sensor for cure degree monitoring, with meander-shaped deformable interconnections. The developed sensor system is able to withstand the manufacturing process where change of pressure and internal strain, thus force exerted on the sensor system, is involved

Non-destructive evaluation of an infusion process using capacitive sensing technique

In this study, a capacitive sensing based non-destructive evaluation technique is applied to a vacuum assisted resin infusion process for the fabrication of glass fibre reinforced composites, as such different steps of the fabrication process (the injection of resin, the curing and the post curing) can be better understood to increase the quality of the fabricated part and reduce the fabrication costs. An interdigital coplanar capacitive sensor was designed, fabricated, and embedded in the glass fibre reinforced composites. Experimental data clearly shows different stages of the resin infusion process: wetting of the glass fibres marked by rapid increase of capacitance; domination of ionic conduction at the early stage of the cure when the resin is still in a liquid state; the vitrification point, indicating a transition of the resin from a gelly state to a glassy state, marked by the relatively big decrease in capacitance; further polymerization during post-curing, marked by a peak in capacitance at the beginning of post-curing cycle, and finally the completion of the cure marked by the saturation of capacitance to a final value. The different phenomena observed during the experiment can be used as a tool for in situ on-line monitoring of composites cure

Prethodna fitocenološka interpretacija vegetacije s vrstom Quercus trojana Webb na brežuljkastim terenima između Barija i Taranta

Here we propose a preliminary interpretation of phytosociological dynamism of the coenoses linked to the presence of Quercus trojana Webb in the Murge region between Bari and Taranto (Apulia — South Italy). It appears that Quercus trojana Webb has placed itself between the lower level of Quercetalia pubescentis-petraeae stage, and the upper of Quercetea ilicis, even if microclimatic situations create many interpretation problems.Na brežuljkastim terenima u području Barija i Taranta postoje još ostaci šuma s vrstom Quercus trojana Webb koje su nekad bile mnogo raširenije. Danas su zajednice s tim hrastom vrlo utjecajne te su razvijene kao šume panjače ili pak kao otvorene šumske sastojine koje se iskorištavaju kao pašnjak; radi se svakako o sastojinama koje je fitoce- nološki teško odrediti a da se ne prave hipoteze o onome što bi moglo biti umjesto onoga što jest. Za početak se, uz naznaku pojedinih fitocenoloških jedinica predlaže klasifikacija sastojina s vrstom Quercus trojana Webb i mogući dina- mizam na granici između sveza Quercion ilicis i Quercion pubescentis-petraeae. Razred: Quercetea ilicis Red: Quercetalia ilicis Asoc: Quercetum ilicis Subas. quercetosum trojanae Asoc: Quercetum trojanae Subas. pistacietosum lentisci Subas. quercetosum pubescentis Subas. quercetosum cerris Subas. quercetosum cocciferae Te sastojine mogu se i isprepletati stvarajući tako brojne prijelazne stadije. Naravno to su pretpostavke koje će naknadno biti istražene i provjerene

RTM production monitoring of the A380 hinge arm droop nose mechanism: a multi-sensor approach

his research presents a case study of production monitoring on an aerospace composite component: the hinge arm of the droop nose mechanism on the Airbus A380 wing leading edge. A sensor network composed of Fibre Bragg Gratings, capacitive sensors for cure monitoring and thermocouples was embedded in its fibre reinforced lay-up and measurements were acquired throughout its Resin Transfer Moulding production process. Two main challenges had to be overcome: first, the integration of the sensor lines in the existing Resin Transfer Moulding mould without modifying it; second, the demoulding of the component without damaging the sensor lines. The proposed embedding solution has proved successful. The wavelength shifts of the Fibre Bragg Gratings were observed from the initial production stages, over the resin injection, the complete curing of the resin and the cooling-down prior to demoulding. The sensors proved to be sensitive to detecting the resin flow front, vacuum and pressure increase into the mould and the temperature increase caused by the resin curing. Measurements were also acquired during the post-curing cycle. Residual strains during all steps of the process were derived from the sensors’ wavelength shift, showing values up to 0.2% in compression. Moreover, the capacitive sensors were able to follow-up the curing degree during the production process. The sensors proved able to detect the resin flow front, whereas thermocouples could not measure an appreciable increase of temperature due to the fact that the resin had the same temperature as the mould

Zajednice hrasta oštrika (Quercus coccifera s. l.) na obalama u području Otranta (Lecce — južni dio Puglie — Italija)

The Authors present the description of a spiny oak (Quercus coccifera s. 1.) station near Otranto and propose a phytosociological interpretation connected to the local vegetational dynamism. The coenosis is part of the degradation series of Quercion ilicis leading to Oleo-Ceratonion of secondary origin.Fitocenološko istraživanje pojedinih zajednica hrasta oštrika (Quercus coccifera) uz obalu otrantskog područja (južni dio Puglie) potvrdilo je ono što je već prije primijećeno u drugim područjima Puglie s obzirom na njihovu fitocenološku pripadnost. Snimljene sastojine pokazuju, zapravo, jasnu tendenciju razvitka prema svezi Quercion ilicis više nego prema svezi Oleo-Ceratonion; ono isto što se događa u sjeverozapadnim područjima areala hrasta oštrika. Smatra se, na temelju dinamičnosti vegetacije, da je to područje vrlo blisko ass. Cocciferetum Br.-Bl. 1924; čak mnogi degradacijski aspekti slijede »provansalsku« shemu s osobitom pojavom vrste Brachypodium izražene u subass. brachypodietosum Br.-Bl. 1951. unutar as. Quercatum ilicis galloprovinciale