José Luís Soares Esteves

Single Filament Mechanical Characterisation of Hemp Fibres for Reinforcing Composite Materials

The work described in this paper refers to the mechanical characterisation of Portuguese hemp fibres, to be used on the production of composite materials with an epoxy matrix. A single filament mechanical characterisation is made, for fibres with and without a cleaning bath from a solution of sodium hydroxide, with the propose of increasing the adherence fibre/matrix.

Thermal characterization of polyhydroxyalkanoates and poly(lactic acid) blends obtained by injection molding

In this work we present the thermal characterization of the full scope of polyhydroxyalcanoate and poly(lactic acid) blends obtain by injection molding. Blends of polyhydroxyalcanoate and poly(lactic acid) (PHA/PLA) were prepared in different compositions ranging from 0–100% in steps of 10%. The blends were injection molded and then characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and wide angle X-ray diffraction (WAXD). The increment of PHA fraction increased the degree of crystallinity of the blend and the miscibility of the base polymers as verified by the Fox model. The WAXD analysis indicates that the presence of PHA hindered the PLA crystallization. The crystallization evolution trough PHA weight fraction (wf) shows a phase inversion around 50-60%. SEM analyses confirmed that the miscibility of PHA/PLA blends increased with the incorporation of PHA and became total for values of PHA higher that 50%. GRAPHICAL ABSTRACT

Mechanical characterization of polyhydroxyalkanoate and poly(lactic acid) blends

In this work, the mechanical behavior of polyhyroxyalkanoate (PHA)/poly(lactic acid) (PLA) blends is investigated in a wide range of compositions. The mechanical properties can be optimized by varying the PHA contents of the blend. The flexural and tensile properties were estimated by different models: the rule of mixtures, Kerner–Uemura–Takayanagi (KUT) model, Nicolai–Narkis model and Béla–Pukánsky model. This study was aimed at investigating the adhesion between the two material phases. The results anticipate a good adhesion between both phases. Nevertheless, for low levels of incorporation of PHA (up to 30%), where PLA is expectantly the matrix, the experimental data seem to deviate from the perfect adhesion models, suggesting a decrease in the adhesion between both polymeric phases when PHA is the disperse phase. For the tensile modulus, a linear relationship is found, following the rules of mixtures (or a KUT model with perfect adhesion between phases) denoting a good adhesion between the phases over the composition range. The incorporation of PHA in the blend leads to a decrease in the flexural modulus but, at the same time, increases the tensile modulus. The impact energy of the blends varies more than 157% over the entire composition. For blends with PHA weight fraction lower than 50%, the impact strength of the blend is higher than the pure base polymers. The highest synergetic effect is found when the PLA is the matrix and the PHA is the disperse phase for the blend PHA/PLA of 30/70. The second maximum is found for the inverse composition of 70/30. PLA has a heat-deflection temperature (HDT) substantially lower than PHA. For the blends, the HDT increases with the increment in the percentage of the incorporation of PHA. With up to 50% PHA (PLA as matrix), the HDT is practically constant and equal to PLA value. Above this point (PHA matrix), the HDT of the polymer blends increases linearly with the percentage of addition of PHA.

Psychological and Cognitive Aspects of Ageing: The Importance of Driving on Senior Living

This research aims to understand the psychological, the social and cognitive aspects of ageing and assess the relevance of driving a personal automobile to seniors. We know that biological ageing is an inescapable fact, but is there also a psychological and a cognitive ageing? If so, is it related to getting older or to other factors? How relevant is continuing to drive to seniors, and how can the activity influence psychological and cognitive types of their ageing and self well-being? To answer these questions, we study several authors and concepts about mental health, development of ageing and their relationship to driving. We also explore psychological and cognitive changes associated with ageing, the principal behavioural changes of healthy senior people (with normal cognitive function) and MCI (mild cognitive impairment), as well as how driving inhibition can induce and affect psychological and cognitive characteristics. We conclude that low mental functioning is caused by a set of biological, psychological and social factors, connected in turn to environmental factors. The slowdown of cognitive activities and performances in seniors is not inevitably accompanied by a decrease in intellectual capacity, low sensory acuity, or slowing psychomotor skills. Other factors should be considered—such as health status, limitations, anxiety, lack of interest, motivation and attitudes. The loss of cognitive abilities and the prevalence of mild cognitive impairment increase with age and are a growing concern, especially among seniors who drive cars. However, we still lack specific evidence based on tests and criteria—in particular, on psychological and cognitive domains—to assess senior drivers actually at risk. It is important to establish a base of evidence to allow objective risk determination. The safest senior drivers should continue driving for as long as possible, thereby contributing to their mental health, independence and quality of life.

Characteristics and human factors of older drivers: improvement opportunities in automotive interior design

This paper analyses the characteristics and human factors of older drivers and how those can influence the driving experience. This research analyses recent studies in ergonomics, interaction and influence of the technologies applied to design of the physical interfaces and their respective in-vehicle devices, with the aim of identifying improvement opportunities in enabling usability design for on-board tasks. The research methodology is descriptive with a collection of baseline studies within the auto industry, ergonomics, health and the mobility and behaviour of older drivers. It is concluded that even the latest car models do not fully provide the highest levels of safety and comfort that could be achieved, with some manufacturers opting to include extra resources to mitigate the changes that result from ageing and driving. It is suggested to create automotive interior design recommendations in a way that improves the safety, comfort and inclusion of older drivers.

The Use of Cellulosic Fibers Wastes to Increase the Mechanical Behaviour of Biodegradable Composites for Automotive Interior Parts

The best way to obtain cellulosic fibers is to use the pulp wastes from the paper plants. The pre-processing of the fibers is a very complex and chemically heavy set of operations. At the end, a small part of the fibers will be rejected and removed from the production system. Actually these rejected fibers are being incinerated at the furnace that dries the raw-wood. This means that after a set of chemical treatments, that ends with a bleach, the fibers will be incinerated driving to a waste of money, once that all the efforts applied to the treatment are not useful, and by other side, the incineration can release some non-healthy emissions. It is possible to use these rejected fibers in composite applications where their mechanical properties can improve the matrix performance. We will present in this paper the influence of incorporation of these rejected fibers into a biodegradable PLA and PHA blended matrix to replace, in some applications, the petrol-based polymers used into the automotive interior trims. The mechanical, and thermal properties will be assessed and compared with the properties of the petrol-polymers normally used in this type of applications.

Skeletal deterioration following ovarian failure: can some features be a direct consequence of estrogen loss while others are more related to physical inactivity?

AbstractFindings on experimental animals show that ovarian failure is a ccompanied by a decrease in motor activity. As mechanical loading has a vital role in the maintenance of skeletal health, our aim was to determine to what extent this decrease in motor activity contributes to ovariectomy-induced bone loss. Thirty-two female Wistar rats were ovariectomized or sham-operated and housed in standard cages or with access to running wheels for 36 weeks with their running distance monitored. Markers of bone turnover were assayed in the serum, and bone geometry, trabecular and cortical bone microarchitecture, mineralization degree, and biomechanical properties were assessed in the femur. Differences between groups were determined by one-way ANOVA. Although reduced motor activity and sex steroid deficiency both resulted in decreases in trabecular bone volume, trabecular number decreases were mostly associated with sex steroid deficiency, whereas trabecular thickness decreases were mostly associated with sedentary behavior. Cortical bone appeared to be more sensitive to variations in motor activity, whereas bone turnover rate and bone tissue mineralization degree seemed to be primarily affected by sex steroid deficiency, even though they were further aggravated by sedentary behavior. Increases in femur length were mostly a consequence of sex steroid deficiency, whereas femoral neck length was also influenced by sedentary behavior. Differences in mechanical properties resulted mostly from differences in physical activity. Both the direct effect of sex steroid deficiency and the indirect effect of motor activity changes are implicated in bone loss following ovariectomy.

Analyses of Composite Structures Behaviour with Embedded Bragg Grating Sensors

Structural health monitoring of composite structures may be accomplished by measuring strains with embedded optical fibre sensors. In this paper, we present the performance of Bragg grating sensors, which are embedded into a carbon composite laminate and them bonded to the structure in analyse. The paper will briefly discuss the results and compare them with a free fibre Bragg grating bonded in the surface of the carbon composite laminate, with existing electrical strain gauge installation and with a numerical analysis by the finite element method.

Metallic End-Bonded Inserts for Pultruded Fibre-Reinforced Plastic Rod

Abstract. The development of new structural applications for the unidirectional pultruded glass-fiber and carbon-fiber reinforced plastic rod, needs the transmission of a considerable tension load to the composite rod, without local damage at the end of the rod. For this purposes we have developed a new kind of metallic end bonded insert, with easy assemblage to the composite rod. These minimises stress concentrations, allowing a good transfer of tensions loads without premature failure of the rod. The methodology behind the development of these metallic inserts is explained with experimental and numerical data verifying the improvements.