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In this study, nutritional composition (protein, lipids, carbohydrates, ash, and moisture), physicochemical properties (soluble solid content, titratable acidity, texture and instrumental colour on surface, and internal section), phytochemicals (total phenolic content and anthocyanin content), and antioxidant capacity (DPPH-2,2 -diphenyl-1-picrylhydrazyl radical scavenging capacity and ferric-reducing antioxidant power) of three strawberry (Fragaria × ananassa Duch.) cultivars (cv. "Primoris", cv. "Endurance", and cv. "Portola") produced in the western region of Portugal (Caldas da Rainha) were evaluated. From the obtained, results no significant differences (P > 0.05) in nutritional composition were detected in all of the cultivars; with the exception of lower protein content observed in cv. "Portola" (0.57 g/100 g ± 0.04; P < 0.05). Regarding the a* value of whole strawberry fruits, no significant differences (P > 0.05) were found in any of the cultivars, which revealed a similar redness. The cv. "Endurance" revealed the highest bioactivity content compared to the other cultivars. Overall, these results provide important information about the high quality of strawberry produced in the western region of Portugal and may be used as a tool for adding value to a functional food in the Mediterranean diet due to the phytochemical composition and nutritional value of strawberry fruits

Optical fibre Bragg grating (FBG) sensors are now quite established and widely used in strain measurements of composites. However, insufficient understanding of the limitations of the embedment and measuring techniques often lead to inaccurate and inconclusive results. In this study, a novel method to improve the reliability and accuracy of the strain measurements on unidirectional composites using embedded FBG sensors was successfully developed. Using a carbon/epoxy prepreg system, test specimens were manufactured with longitudinally embedded FBG sensors. The combined behaviour of the sensors and the host material was characterized and a calibration rule (correction factor) was determined for the chosen material. The consistency of the results with both theoretical and empirical assumptions suggests that the proposed method is applicable to a wide range of FBG sensors and host materials.

In this work, the load sharing ability of metallic liners in type III composite overwrapped pressure vessel was investigated by means of accurate numerical models based on finite element method in order to realistically represent the hybrid metal-composite structure. The varying thickness of the composite layers throughout the dome, as well as their angles, were accounted for in the model. The study focused on the influence of material properties and liner-to-composite thickness ratio on the stress and strain distribution between liner and composite at the cylindrical, dome, and polar boss regions. Two novel concepts for the evaluation of the structural response of a composite overwrapped pressure vessel were introduced, namely: (i) the liner stress and strain fractions, and (ii) the correlation with liner-to-composite thickness ratio. The results show complex overall behavior close to the onset of plasticity of the liner, which is critically investigated. A decrease in liner stress fraction was found for higher internal pressure loads since the stress field is increasingly dominated by the composite overwrap. Also, the von Mises equivalent stress along the longitudinal profile of the structure showed a peak at the dome of the liner, whereas for the composite, the peak was at the shoulder region. This was justified considering that, at low pressure, the liner operates elastically in compression-tension mode and the composite in tension-tension mode.

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The aim of this work was to study the long‐term failure of GRP (Glass fiber‐reinforced Polymer) pipes under the influence of moisture absorption. These pipes are used in water transportation, which has an important effect on the mechanical properties of the polymeric matrix. The GRP pipes are usually tested under ring deflection or internal pressure conditions. This study presents and analyzes experimental creep‐rupture data obtained from standard test methods under ring deflection conditions. This loading configuration simulates in laboratory the conditions verified in a subsoil installation. The creep testing was carried out under constant dead weight on unconditioned and preconditioned samples in a submerged condition. The diametrical deflection of samples was measured periodically, and the time to failure of each sample was recorded. The main purpose of this work was to determine the short and long‐term rupture energies of GRP pipes and assess the influence of moisture preconditioning on those values. The observed failure mode was always the same. It was concluded that the energy at failure decreases with time. The influence of the preconditioning on the creep‐rupture of GRP pipes was considered negligible. Different time‐dependent failure models were described and used for long‐term extrapolation of the experimental data. The maximum strain at failure decreased about 12% from 0.1 to 1,000 hr of creep testing. Furthermore, data extrapolation to 50 years predicts a reduction of strength of about 60%, founded on the most conservative time‐dependent failure criterion. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

a b s t r a c tOptical fibre Bragg grating (FBG) sensors are now quite established and widely used in strain measurements in composites. However, insufficient understanding of the limitations of the embedment and measuring techniques often leads to inaccurate results. This work is a continuation of a novel method to improve the reliability and accuracy of the strain measurements on unidirectional composites using embedded FBG sensors [1]. A new combination of the pair host material/sensor was studied and characterized. Test specimens were manufactured with longitudinally embedded FBG sensors, using a glass/ epoxy prepreg system, in order to compare with a carbon/epoxy prepreg system. The combined behaviour of the sensors and the host material was characterized and a procedure to obtain a more accurate strain was defined for this new chosen material.

In this research programme, methodologies for structural health monitoring (SHM) of composite overwrapped pressure vessels (COPV) were addressed. So, this work is part of the development of a COPV laboratorial prototype incorporated with non-destructive sensing technologies. The aim is to detect and identify critical aspects that can happen during operation, in order to reduce possible safety problems. Fibre Bragg grating (FBG) optical sensors and polyvinylidene fluoride (PVDF) polymeric piezoelectric were the selected sensing technologies. These sensors were embedded in the liner-composite interface during its manufacturing and monitored the prototype while tested under cyclic internal pressure loading. The measurements collected from the sensors were compiled with the analysis of test data and are presented in this paper. Also, the suitability of the two sensing technologies, issues related to sensor embedding and the monitoring strategy are discussed.