Study of plant fibre composites with damage induced by laser and mechanical impacts

Polymer composite materials provide good strength to weight ratio and tailored mechanical properties thanks to the reinforcing fibres. Until recently, the need for taking into account the whole life cycle of a composite structure was neglected and only the service aspects were important. Today, the designers of a new composite structure have to take into account the environmental aspects from the sustainability of raw materials to the management of end life products. There are recycling issues related to the most popular composites. A solution for the recycling issue can be sought in green composites with reinforcing fibre originating from plants. The behaviour of eco-composites, when subjected to laser or mechanical impact loadings, is not well known yet. Short fibre composites were made with spruce fibres. Another set of samples was made of flax fibres. Also a woven hemp fabric-based eco-composite was investigated. A fully synthetic woven composite was used for comparison with green composites. Mechanical impacts were performed by means of a falling dart impact testing machine. Laser impacts were made with high power laser source. Four assessment techniques were employed in order to analyse and compare impact damage. Damage detection thresholds for each material and technique were obtained

Fatigue behaviour before and after impact of woven hemp/epoxy composite

Cette étude porte sur un composite de tissu de chanvre et matrice époxy. Des essais ont d’abord été réalisés sur les constituants. Ils ont montré que le comportement des fils imprégnés par de la résine est plus représentatif du comportement dans le composite que celui des fils secs. Ces essais ont aussi permis de déterminer les paramètres matériaux nécessaires pour l’élaboration d’un modèle par éléments finis d’un pli du composite. Ce modèle est basé sur une simplification de la représentation du tissu. La variabilité des propriétés des constituants a été prise en compte. Les champs de déformation ont été comparés avec ceux mesurés par la technique de DIC à la surface des composites. Des essais de fatigue ont été réalisés sur les composites [0°/90°]7 et [±45°]7. L’échauffement a été mesuré par caméra IR, les endommagements ont été suivis par EA et par une caméra haute résolution. Des observations ont été effectuées par microscopie et par microtomographie X. Une analyse approfondie des mécanismes d’endommagement a été réalisée. Un modèle de courbe SN de fatigue a été adapté aux composites chanvre/époxy étudiés. La tenue à l’impact et le comportement mécanique postimpact du composite chanvre/époxy [0°/90°]7 ont été étudiés. Les résultats ont montré l’influence d’un impact non destructif sur la durée de vie en fatigue de ce composite, et l’évolution de l’endommagement a été analysée. Il a été montré que le modèle des courbes S-N de fatigue peut s’appliquer aux éprouvettes impactées. Il est ainsi possible de prédire la durée de vie en fatigue du composite impacté à partir de sa contrainte à rupture en traction et du comportement en fatigue du matériau sain.This study focuses on a woven hemp/epoxy composite. Tests were first conducted on its components. They showed that the behaviour of resin impregnated yarn is more representative of the yarn behaviour in the composite than the dry yarn usually studied. These tests were also used to determine the material parameters necessary for the development of a finite element model of a composite ply. This model is based on a simplified representation of the fabric. Variability of properties of the components was taken into account. Strain fields were compared with those measured by the DIC technique on the surface of the composites. Fatigue tests were conducted on composites [0°/90°]7 and [±45°]7. Heating was measured by IR camera; the damage was followed by AE and high resolution camera. Observations were made by microscopy and X-ray microtomography. A detailed analysis of damage mechanisms was performed. A model of S-N fatigue curve was adapted to the studied hemp/epoxy composite. The resistance to impact and the post-impact mechanical behaviour of the [0°/90°]7 hemp/epoxy composite were studied. The results showed the influence of a non-destructive impact on the fatigue life of the composite, and the evolution of the damage was analyzed. It has been shown that the model of S-N fatigue curve can be applied to impacted specimens. It is thus possible to predict the fatigue life of the impacted composite from the tensile strength and fatigue behaviour of the non-impacted material

Comportement en fatigue avant et après impact de composites tissés chanvre/époxy

This study focuses on a woven hemp/epoxy composite. Tests were first conducted on its components. They showed that the behaviour of resin impregnated yarn is more representative of the yarn behaviour in the composite than the dry yarn usually studied. These tests were also used to determine the material parameters necessary for the development of a finite element model of a composite ply. This model is based on a simplified representation of the fabric. Variability of properties of the components was taken into account. Strain fields were compared with those measured by the DIC technique on the surface of the composites. Fatigue tests were conducted on composites [0°/90°]7 and [±45°]7. Heating was measured by IR camera; the damage was followed by AE and high resolution camera. Observations were made by microscopy and X-ray microtomography. A detailed analysis of damage mechanisms was performed. A model of S-N fatigue curve was adapted to the studied hemp/epoxy composite. The resistance to impact and the post-impact mechanical behaviour of the [0°/90°]7 hemp/epoxy composite were studied. The results showed the influence of a non-destructive impact on the fatigue life of the composite, and the evolution of the damage was analyzed. It has been shown that the model of S-N fatigue curve can be applied to impacted specimens. It is thus possible to predict the fatigue life of the impacted composite from the tensile strength and fatigue behaviour of the non-impacted material.Cette étude porte sur un composite de tissu de chanvre et matrice époxy. Des essais ont d’abord été réalisés sur les constituants. Ils ont montré que le comportement des fils imprégnés par de la résine est plus représentatif du comportement dans le composite que celui des fils secs. Ces essais ont aussi permis de déterminer les paramètres matériaux nécessaires pour l’élaboration d’un modèle par éléments finis d’un pli du composite. Ce modèle est basé sur une simplification de la représentation du tissu. La variabilité des propriétés des constituants a été prise en compte. Les champs de déformation ont été comparés avec ceux mesurés par la technique de DIC à la surface des composites. Des essais de fatigue ont été réalisés sur les composites [0°/90°]7 et [±45°]7. L’échauffement a été mesuré par caméra IR, les endommagements ont été suivis par EA et par une caméra haute résolution. Des observations ont été effectuées par microscopie et par microtomographie X. Une analyse approfondie des mécanismes d’endommagement a été réalisée. Un modèle de courbe SN de fatigue a été adapté aux composites chanvre/époxy étudiés. La tenue à l’impact et le comportement mécanique postimpact du composite chanvre/époxy [0°/90°]7 ont été étudiés. Les résultats ont montré l’influence d’un impact non destructif sur la durée de vie en fatigue de ce composite, et l’évolution de l’endommagement a été analysée. Il a été montré que le modèle des courbes S-N de fatigue peut s’appliquer aux éprouvettes impactées. Il est ainsi possible de prédire la durée de vie en fatigue du composite impacté à partir de sa contrainte à rupture en traction et du comportement en fatigue du matériau sain

Comportement en fatigue avant et après impact de composites tissés chanvre/époxy

Cette étude porte sur un composite de tissu de chanvre et matrice époxy. Des essais ont d abord été réalisés sur les constituants. Ils ont montré que le comportement des fils imprégnés par de la résine est plus représentatif du comportement dans le composite que celui des fils secs. Ces essais ont aussi permis de déterminer les paramètres matériaux nécessaires pour l élaboration d un modèle par éléments finis d un pli du composite. Ce modèle est basé sur une simplification de la représentation du tissu. La variabilité des propriétés des constituants a été prise en compte. Les champs de déformation ont été comparés avec ceux mesurés par la technique de DIC à la surface des composites. Des essais de fatigue ont été réalisés sur les composites [0/90]7 et [+-45]7. L échauffement a été mesuré par caméra IR, les endommagements ont été suivis par EA et par une caméra haute résolution. Des observations ont été effectuées par microscopie et par microtomographie X. Une analyse approfondie des mécanismes d endommagement a été réalisée. Un modèle de courbe SN de fatigue a été adapté aux composites chanvre/époxy étudiés. La tenue à l impact et le comportement mécanique postimpact du composite chanvre/époxy [0/90]7 ont été étudiés. Les résultats ont montré l influence d un impact non destructif sur la durée de vie en fatigue de ce composite, et l évolution de l endommagement a été analysée. Il a été montré que le modèle des courbes S-N de fatigue peut s appliquer aux éprouvettes impactées. Il est ainsi possible de prédire la durée de vie en fatigue du composite impacté à partir de sa contrainte à rupture en traction et du comportement en fatigue du matériau sain.This study focuses on a woven hemp/epoxy composite. Tests were first conducted on its components. They showed that the behaviour of resin impregnated yarn is more representative of the yarn behaviour in the composite than the dry yarn usually studied. These tests were also used to determine the material parameters necessary for the development of a finite element model of a composite ply. This model is based on a simplified representation of the fabric. Variability of properties of the components was taken into account. Strain fields were compared with those measured by the DIC technique on the surface of the composites. Fatigue tests were conducted on composites [0/90]7 and [+-45]7. Heating was measured by IR camera; the damage was followed by AE and high resolution camera. Observations were made by microscopy and X-ray microtomography. A detailed analysis of damage mechanisms was performed. A model of S-N fatigue curve was adapted to the studied hemp/epoxy composite. The resistance to impact and the post-impact mechanical behaviour of the [0/90]7 hemp/epoxy composite were studied. The results showed the influence of a non-destructive impact on the fatigue life of the composite, and the evolution of the damage was analyzed. It has been shown that the model of S-N fatigue curve can be applied to impacted specimens. It is thus possible to predict the fatigue life of the impacted composite from the tensile strength and fatigue behaviour of the non-impacted material.POITIERS-ENS Mécanique Aérot (860622301) / SudocSudocFranceF

Flexural and low velocity impact characterization of thermoplastic composites based on PEN and high performance woven fabrics

Poly(Ethylene 2,6‐Naphthalate)—PEN has been used as matrix for laminates with the aim to develop woven fiber reinforced composites with a service temperature as high as 100°C. Three different classes of fibers have been considered as reinforcement in woven fabric form: carbon, polymers (Twaron and Vectran) and mineral (basalt). Composites were manufactured by using the film stacking technique, alternating layers of balanced plain weave fabrics (0/90) and films of amorphous PEN. The manufacturing process was optimized to obtain a good impregnation of fibers and very low void content. Static flexural tests, dynamic mechanical analysis and low velocity impacts were used to characterize the mechanical behavior of the composites. The flexural modulus and strength of laminates resulted to be very high, in particular for the PEN/Carbon and PEN/Basalt systems. The storage modulus from the dynamic mechanical analysis indicated that 100°C is a suitable service temperature for all configurations. The impact resistance of the composites showed a different trend with respect to static tests, since PEN/Basalt and PEN/Aramid exhibited the best performances. These results prove that PEN is a viable option for the production of structural composites as replacement of thermosetting matrices due to its high performance/cost ratio, in particular when combined with basalt fibers. POLYM. COMPOS., 39:2942–2951, 2018. © 2017 Society of Plastics Engineer

Effect of temperature on static and low velocity impact properties of thermoplastic composites

In this work, thermoplastic composites based on poly(ethylene 2,6-naphthalate) (PEN) have been investigated with the aim to elucidate the effect of temperature on static and impact properties. The matrix was reinforced with four different high performing woven fabrics based on carbon, Twaron, Vectran, basalt fibres. Composites were manufactured by using the film stacking technique, alternating layers of balanced plain weave fabrics (0/90) and films of amorphous PEN, keeping the fibre volume fraction around 40%. The compression moulding process was optimized to obtain optimal fabric impregnation and to keep the void content lower than 1%. The structural response was evaluated at 20 °C, 60 °C and 100 °C by means of static flexural and low velocity impact tests. Dynamic mechanical scans (DMA) were also performed to evaluate the stiffness of the laminates at temperatures ranging from – 80 °C to 230 °C. The flexural modulus and strength of laminates resulted to be very high in proportion with the fibre stiffness. The flexural behaviour was affected by the temperature but a limited reduction of the stiffness (lower than 20%) was exhibited by all but PEN/Vectran up to temperatures of 100 °C. PEN/carbon resulted the best performing system at each testing temperature (flexural modulus equal to 38.8 GPa, flexural strength equal to 714 MPa at 20 °C). Results from DMA tests demonstrated a satisfactory agreement with static tests (differences within ±13%, except that for PEN/Vectran). The impact resistance of the composites was found to depend on the fibre type, temperature and interface strength. PEN/basalt resulted the best performing composite followed by PEN/Twaron (perforation energy at 20 °C: 44.3 J and 38.2 J, respectively). The PEN/carbon laminate exhibited the lowest impact performance but, unlike PEN/basalt and PEN/Vectran, the impact resistance improved with the increasing temperature

Thermoplastic composites based on poly(ethylene 2,6-naphthalate) and basalt woven fabrics. Static and dynamic mechanical properties

Composites based on poly(ethylene 2,6‐naphthalate) and basalt woven fabrics have been investigated with the aim to develop composites with a minimum service temperature of 100°C. Laminates have been manufactured by using the film‐stacking technique. A very low void content and a good fabric impregnation has been obtained as confirmed by the morphological analysis performed with scanning electron microscopy. Static flexural modulus and strength have been measured at 20, 60, and 100°C and compared with the dynamic mechanical behavior, evaluated from −100 to 220°C. A very good agreement has been detected between static and dynamic tests, proving that the dynamic mechanical analysis can be used to estimate the flexural modulus in a wide temperature range. Poly(ethylene 2,6‐naphthalate)/basalt composites have exhibited (at 20°C) a flexural modulus and strength as high as 20 GPa and 320 MPa, respectively. The flexural modulus and the flexural strength at 100°C have been found to be equal to 18 GPa and 230 MPa, confirming that this system can retain very good mechanical properties at a service temperature of 100°

Cryolipolysis: patient selection and special considerations

Patricia Froes Meyer,1 Julio Davi Costa e Silva,2 Liliane Santos de Vasconcellos,3 Eneida de Morais Carreiro,4 Rodrigo Marcel Valentim da Silva5,6 1Department of Physiotherapy, Potiguar University, Natal, Brazil; 2Department of Physiotherapy, Potiguar University – UnP, Natal, Brazil; 3Department of Physical Therapy, Potiguar University – UnP, Natal, Rio Grande do Norte, Brazil; 4Center University of Rio Grande do Norte, Physiotherapy Department, Natal, Brazil; 5Estácio de Sá University, Physiotherapy Department, Natal, Brazil; 6Mauricio de Nassau College, Physiotherapy Department, Natal, Brazil Abstract: Cryolipolysis is considered a safe and effective procedure, with high patient satisfaction rates, especially when compared to other procedures for localized adiposity, such as high-intensity focused ultrasound and shock waves. Although this statement is present in the literature, the importance of the selection of suitable patients for this type of treatment is not well known. The objective of this study was to discuss the criteria to be considered in the selection of patients who are candidates for cryolipolysis and assess their profile regarding their anthropometric data, age, skin characteristics, cutaneous sensitivity, and risk pathologies for this type of treatment. Assessing the amount of localized adiposity requires safe and validated methods that are significant in measuring results. The aim is to achieve success in the process of reducing adiposity guaranteeing patient satisfaction and assurance of results. Keywords: adiposity, dermatologic physical therapy, cryolipolysi

Environmental Monitoring and Assessment

Texto completo: acesso restrito. p. 2663-2676In this study, particulate matter (PM) were characterized from a place impacted by heavy-duty vehicles (Bus Station) fuelled with diesel/biodiesel fuel blend (B3) in the city of Londrina, Brazil. Sixteen priority polycyclic aromatic hydrocarbons (PAH) concentrations were analyzed in the samples by their association with atmospheric PM, mass size distributions and major ions (fluorite, chloride, bromide, nitrate, phosphate, sulfate, nitrite, oxalate; fumarate, formate, succinate and acetate; lithium, sodium, potassium, magnesium, calcium and ammonium). Results indicate that major ions represented 21.2% particulate matter mass. Nitrate, sulfate, and ammonium, respectively, presented the highest concentration levels, indicating that biodiesel may also be a significant source for these ions, especially nitrate. Dibenzo[a,h]anthracene and indeno[1,2,3,-cd]pyrene were the main PAH found, and a higher fraction of PAH particles was found in diameters lower than 0.25 μm in Londrina bus station. The fine and ultrafine particles were dominant among the PM evaluated, suggesting that biodiesel decreases the total PAH emission. However, it does also increase the fraction of fine and ultrafine particles when compared to diesel