•Ballistic performance of composite Kevlar® 29/epoxy laminates were evaluated experimentally and by means of numerical models.•Ballistic capability of the composite show differences considering ...different soft-core actual projectiles and target thicknesses.•Extended material characterization was performed for the model development.•Damage mechanisms were found to be strongly affected by the thickness of the laminates.
Ballistic impact loading is one of the most critical conditions to which structures can be subjected, and the selection of materials to be used is of fundamental importance. Kevlar® is considered one of the most efficient fiber, offering high protection against fragmentation and ballistic threats with reduced weight and thickness. In this work, ballistic behavior of aramid/epoxy composites plates of various thicknesses produced by vacuum infusion and impacted by actual projectiles of different geometries were studied through experimental and numerical approach. An extended testing campaign to evaluate material behavior in different loading cases was essential for an accurate definition of the material model. Residual velocity of the projectiles and energy absorbed by the composites were measured during ballistic tests. The damage mechanisms caused by the impact of the projectiles were analyzed through photographic and X-ray images and compared with numerical results. The energy absorption capacity and damage mechanisms were found to be strongly affected by the thickness of the material. Numerical predictions were consistent with experimental results both in terms of residual velocity and damage morphology, and some disagreement was found when the impact velocity approached the ballistic limit. The developed numerical model was used to produce the ballistic curve for different combinations of plates and projectiles, allowing comparison of panel efficiency for different thicknesses.
Wind blades, an important application of polymeric composite materials, are subject to natural weathering. This study aims to evaluate mechanical, thermal and morphological behavior during ...accelerated aging in three thicknesses of epoxy and fiberglass polyurethane-coated composite plates used in wind turbines, in addition to testing with two acoustic emission techniques. An accelerated aging chamber simulated natural weathering mechanisms for 45, 90, 135 and 180 days. This degradation primarily reduced the mechanical properties of the thinner composites, with some damaged specimens exhibiting fiber-matrix debonding. Thermal properties deteriorated. There were no morphological changes on the polyurethane–epoxy interface; however, degradation occurred in the fiber-matrix interface on the surface exposed to radiation. The degree of chalking indicated coating deterioration on the external surface of the polyurethane. The acoustic wave propagation speed and attenuation coefficient measured prior to mechanical testing indicated the presence of damage areas.
Active flexible composites can be developed through the coupling of silicone matrices and smart materials such as NiTi shape memory alloys (SMA). This work evaluates the mechanical behavior and ...adhesion of NiTi SMA ribbons embedded in a silicone matrix for the development of active flexible composites. Ribbons with cross-section of 0.15 × 0.8 mm2 were cold-rolled from superelastic NiTi wires with 0.4 mm in diameter. These ribbons were heat treated to either obtain characteristics of superelasticity (SE) or shape memory effect (SME) at room temperature. Silicone, NiTi wire, and ribbons were characterized by Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), and tensile tests. Adhesion between SMA ribbons and silicone matrix was evaluated with pull-out tests. The use of an adhesion promoter proved to be indispensable to ensure a good pull-out strength and shear stress at the NiTi ribbon and silicone interface. A silicone rubber cylinder with an embedded SME ribbon was built to evaluate the functionality of the NiTi ribbon in the development of flexible structures, which was demonstrated by the resistive heating and deformation of the SMA/silicone rubber composite.
Selective Surfaces of Ilmenite for Use in Solar Absorbers Sousa, Gustavo César Pamplona de; Gomes, Kelly Cristiane; Amorim Júnior, Wanderley Ferreira de ...
Materials research (São Carlos, São Paulo, Brazil),
2021, Letnik:
24, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract The world is moving at a fast pace in the consumption of non-renewable natural resources, causing several ecological problems. The search for the cost reduction by implementing renewable ...energies implies in the optimization of the manufacturing processes parameters of consolidated technologies, such as solar thermal energy collectors. One of the applications of selective surfaces is to improve performance of solar absorbers. The purpose of this work is to produce selective coatings with high absorption in range of UV/Vis and low emittance in the IR range. It was prepared a selective surface composed of ilmenite deposited on substrates of AISI 304 stainless steel using technique of cathodic cage plasma nitriding/deposition for application in solar thermal absorbers. Ilmenite was initially characterized by X-Ray Diffractometry (XRD), X-Ray Fluorescence (FRX) and Thermal Analysis (TGA). The coatings produced were optically characterized in range UV/Vis/IR and emittance and data on the roughness parameters of the films were obtained by Optical Profilometry. Selective surfaces with high solar absorbance (87%) compared with state-of-the-art commercial ones (70-80%) and low thermal emission (14%) compared with state-of-the-art commercial ones (20-30%) were obtained by validating the potential of ilmenite to produce selective surfaces for thermal solar collectors.
Vaginal laxity: what does this symptom mean? Dietz, Hans Peter; Stankiewicz, Martyna; Atan, Ixora Kamisan ...
International Urogynecology Journal,
05/2018, Letnik:
29, Številka:
5
Journal Article
Recenzirano
Introduction and hypothesis
Vaginal laxity is a poorly understood symptom of pelvic floor dysfunction. The purpose of this study was to investigate associations between the symptom of vaginal laxity ...and its bother on the one hand, and demographic data, other symptoms, and findings on examination on the other hand.
Methods
This was a retrospective observational study at a tertiary urogynecological unit. A total of 337 patients were seen for a standardized interview, clinical examination (ICS POP-Q) and 4D translabial ultrasonography. Stored imaging data were analyzed offline to evaluate functional pelvic floor anatomy and investigate associations with symptoms and other findings.
Results
Of the 337 women seen during the study period, 13 were excluded due to missing data, leaving 324. Vaginal laxity was reported by 24% with a mean bother of 5.7. In a univariate analysis, this symptom was associated with younger age, vaginal parity, POP symptoms and bother, clinically and sonographically determined POP and hiatal area on Valsalva maneuver.
Conclusions
Vaginal laxity or ‘looseness’ is common in our urogynecology service at a prevalence of 24%. The associated bother is almost as high as the bother associated with conventional prolapse symptoms. It is associated with younger age, vaginal parity, symptoms of prolapse, prolapse bother and objective prolapse on POP-Q examination and imaging, suggesting that vaginal laxity may be considered a symptom of prolapse. The strongest associations were found with gh + pb and hiatal area on Valsalva maneuver, suggesting that vaginal laxity is a manifestation of levator ani hyperdistensibility.
Association between vaginal parity and rectocele Dietz, Hans Peter; Gómez, Mariángeles; Atan, Ixora Kamisan ...
International Urogynecology Journal,
10/2018, Letnik:
29, Številka:
10
Journal Article
Recenzirano
Introduction and hypothesis
Rectocele is common in parous women but also seen in nulliparae. This study was designed to investigate the association between vaginal parity and descent of the rectal ...ampulla/rectocele depth as determined by translabial ultrasound (TLUS).
Methods
This retrospective observational study involved 1296 women seen in a urogynaecological centre. All had undergone an interview, clinical examination and 4D ultrasound (US) imaging supine and after voiding. Offline analysis of volume data was undertaken blinded against other data. Rectal ampulla position and rectocele depth were measured on Valsalva. A pocket depth of 10 mm was used as a cutoff to define rectocele on imaging.
Results
Most women presented with prolapse (53%,
n
= 686); 810 (63%) complained of obstructed defecation (OD). Clinically, 53% (
n
= 690) had posterior-compartment prolapse with a mean Bp of −1 standard deviation (SD)1.5; −3 to 9 cm. Mean descent of the rectal ampulla was 10 mm below the symphysis (SD 15.8; −50 to 41). A rectocele on imaging was found in 48% (
n
= 618). On univariate analysis, OD symptoms were strongly associated with rectal descent, rectocele depth and rectocele on imaging (all
P
< 0.001). The prevalence of a rectocele seen on imaging increased with vaginal parity (
P
< 0.001). One-way analysis of variance (ANOVA) of vaginal parity against rectal descent and rectocele depth showed a dose–response relationship (both
P
< 0.001).
Conclusions
Vaginal parity was strongly associated with descent of the rectal ampulla and rectocele depth. This relationship approximated dose–response characteristics, with the greatest effect due to the first vaginal delivery.
The aim of this article was to assess the behavior of polymer composites under low-velocity impact considering stress concentrators (two side holes at the point of impact) and determine the residual ...mechanical properties of these materials using FAI (Flexural After Impact). Analysis of residual properties ascertained the effects of damage and stress concentrators, assessing their individual influence in increasing the stress concentration factor (
K
). This analysis was conducted via tests that consider the separate effects of each case and a formulation that relates them. In addition, this paper also assessed the influence of void percentage on the impact and residual strength, developing two E-glass fiber fabric-based composites with different void percentage. The tests performed showed that impact damage increased the concentration factor of the material by 18%, but in samples tested with side holes, damage decreased residual strength by only 5%.
Groundwater plays a vital role in human consumption and irrigation in many parts of Bolivia; yet, the absence of policies to regulate its extraction and protect groundwater recharge areas has led to ...a decline in water tables and threatened food security. Some municipal initiatives have been implemented to develop regulations, but the lack of reliable hydrogeological data (such as aquifer geometry, groundwater level data, location of potential groundwater recharge zones, and flow dynamics) hinders their effective implementation. The case study presented herein focuses on a municipal policy in Tiraque, Bolivia, aimed at protecting groundwater recharge zones, in addition to the need for a reliable methodology for their technical identification. The EARLI approach (an acronym for “Enhanced Algorithm for Recharge based on the Rainfall and Land cover Inclusion”) is suggested as a participatory-simplified multi-criteria decision method to address the absence of hydrogeological data. This approach was adjusted to the basin’s specific conditions, including local vegetation communities and their influence on infiltration, and was applied as a pilot study in the Virvini micro-basin. The EARLI model emphasizes the spatial distribution of rainfall as an input indicator for potential recharge in addition to the biophysical characteristics of the catchment area. The methodology successfully mapped the degree of groundwater recharge potential and was validated by traditional hydrogeological models, field infiltration measurements, and the local community’s application of the tool. Therefore, the results of this study provide the necessary technical bases for groundwater-integrated management in Tiraque.
Abstract The objective of this work was to evaluate the changes in the physicochemical properties of different species of edible flowers in the postharvest period. Flowers of Viola cornuta (light or ...dark colored), Viola tricolor, Antirrhinum majus, Dianthus chinensis, and Tagetes patula were selected, packed, and placed in a cold chamber of the BOD type, at 5±1°C and 90–95% relative humidity. Every two days, fresh weight loss, visual quality using a scale score, and total longevity were evaluated. The total soluble solids (SS) content, titratable acidity (TA), the SS/TA ratio, and pH were also evaluated at the time of harvest and at the end of postharvest life. There was a significant increase in the SS contents of light-colored V. cornuta, V. tricolor, and D. chinensis. A significant reduction in TA was observed in light-colored V. cornuta, V. tricolor, A. majus, and D. chinensis at the end of postharvest life. The pH value increased significantly only in T. patula flowers. The studied species of edible flowers have a short commercial longevity, which varies from 4 to 10 days, while the maximum total longevity varies from 6 to 14 days.
Resumo O objetivo deste trabalho foi avaliar as alterações das propriedades físico-químicas de diferentes espécies de flores comestíveis, no período pós-colheita. Flores de Viola cornuta (de cor clara ou escura), Viola tricolor, Antirrhinum majus, Dianthus chinensis e Tagetes patula foram selecionadas, embaladas e acondicionadas em câmara frigorífica do tipo BOD, a 5±1°C e 90–95% de umidade relativa. A cada dois dias, avaliou-se a perda de massa de matéria fresca, a qualidade visual por escala de notas e a longevidade total. Também avaliou-se o teor de sólidos solúveis (SS) totais, a acidez titulável (AT), a relação SS/AT e o pH, no momento da colheita e ao final da vida póscolheita. Houve aumento significativo nos valores de SS em V. cornuta de cor clara, V. tricolor e D. chinensis. Observou-se a redução da AT de V. cornuta de cor clara, V. tricolor, A. majus e D. chinensis ao final da vida pós-colheita. O valor do pH aumentou significativamente apenas em flores de T. patula. As espécies de flores comestíveis estudadas têm longevidade comercial curta, que varia de 4 a 10 dias, enquanto a longevidade total máxima varia de 6 a 14 dias.
In the last decades, the composite materials were used in the modern ballistic armor systems. Thus, techniques have been developed to predict its mechanical properties, damage mechanisms and strength ...associated to ballistic impact penetration. The objective of this work was the ballistic impact and quasi-static punch shear behavior of fiberglass polymer composites. The materials used in the experiments were: woven fabric and chopped strand mat E-glass fiber and polyester resin. The composites submitted to ballistic impact and quasi-static punch shear tests had 1, 5, 10, 15, and 20 layers and 5, 8, 10, 12, 14, 15, and 20 layers, respectively. A quasi-static punch shear fixture test was developed. The best ballistic performance composite was the 10 layers woven fabric. In quasi-static punch shear test, it was possible to analyze the internal fracture of composites, and the load x displacement behavior was observed.
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