Análise e quantificação do dano em materiais compósitos de matriz polimérica

Os materiais compósitos têm assumido uma importância crescente na engenharia e o seu uso é cada vez mais comum. Características importantes destes materiais, como as elevadas propriedades mecânicas, associadas a maior leveza, têm permitido uma vasta aplicação em áreas tão distintas como a medicina, o desporto, a aeronáutica, a defesa ou a indústria automóvel. A maioria dos compósitos é fabricada sob a forma de peças funcionais, prontas ou quase prontas a serem utilizadas. Contudo, o seu uso ainda não prescinde completamente de processos de maquinagem adicionais, com particular destaque para a furação. Com efeito, a furação de materiais compósitos é ainda um processo muito frequente e, apesar de vários progressos feitos nesta área, deste processo resultam danos nos materiais compósitos cujos efeitos têm de ser tidos em conta. Entre os principais defeitos decorrentes da furação, destaca-se o fenómeno da delaminação. O objetivo deste estudo foi o de avaliar a magnitude da área danificada por furação em carbono epóxido, um material compósito de matriz polimérica, e de que forma os danos decorrentes do processo de furação afetavam as propriedades mecânicas do material. Foram fabricados 35 provetes em carbono epóxido e procedeu-se à furação com cinco geometrias diferentes de broca – broca Helicoidal, broca Dagger, broca Brad, broca High Speed Steel e broca Helicoidal com pré-furação – a fim de se obterem diversas áreas de dano. Os provetes foram radiografados e das imagens resultantes foi possível calcular a área de dano causado por furação, com recurso a software de edição de imagem. No final, os provetes foram submetidos a dois ensaios mecânicos: Flexão em 3 pontos e Pin-Bearing. As áreas de dano determinadas foram relacionadas com a perda de propriedades mecânicas verificadas durante os ensaios com recurso a ferramentas estatísticas. Os resultados obtidos permitiram estabelecer e modelar relações entre a área danificada durante a furação e a resistência mecânica do material. A resistência à flexão não apresenta grande variabilidade em função da área de dano. Já a resistência à compressão diminui com o incremento da área de dano.Composite materials have been assuming a growing importance in engineering and their use is becoming more common. Important characteristics of these materials, such as high mechanical properties along with lightness, have allowed a wide application in distinct areas like medicine, sports, aeronautics, defense or automotive industry. The majority of the composite materials is produced in the form of functional parts, in a net or near-net shape. However, their use does not fully excludes yet the need of additional machining processes, particularly the drilling process. So, the drilling of composite materials remains a very frequent process and, despite several advances in this area, this process causes damages to the composite materials whose effects must be taken in consideration. Among the main problems resulting from drilling, delamination is one of the most important. The objective of this study was to evaluate the magnitude of the area damaged by drilling in carbon epoxy, a composite material with polymeric matrix, and how does the resulting damages of the drilling process affected the mechanical properties of the material. There were manufactured 35 test subjects in carbon epoxy and they were drilled with five different drill geometries – Twist drill, Dagger Drill, Brad drill, High Speed Steel drill and Twist drill with pre-drilling - to obtain different damage areas. The test subjects were then radiographed and from the resulting images it was possible to calculate the damaged area caused by drilling, using an image editing software. Finally, the test subjects went under two mechanical tests: Three point flexural test and Pin-Bearing test. The determined damaged areas were related to the loss of mechanical properties verified during the tests, using statistical tools. The achieved results allowed to establish and model the relations between the damaged area during drilling and the material’s mechanical resistance. The bending resistance does not vary greatly with the damage area. In the other hand, the bearing resistance decreases with the increase of the damage area

Imagem Pipeline: sistema de pipeline para processamento de imagens

Este trabalho surge da necessidade de um desenvolvedor de sistemas, especialista em intelig?ncia artificial, no gerenciamento de diversos servi?os, primordialmente de processamento de imagens, distribu?dos em v?rias APIs. Uma das dificuldades relatadas foi a constru??o de pipeline automatizado que ? um fluxo de processamento de v?rios servi?os computacionais aut?nomos, executados paralelo ou sequencialmente, com intuito de resolver um problema computacional, como a detec??o de placas de tr?nsito. A solu??o proposta foi o desenvolvimento da plataforma Imagem Pipeline, que fornece uma interface para a integra??o com APIs de terceiros e a flexibilidade na cria??o de pipelines personalizados, permitindo a configura??o de fluxos dos processos automatizados a serem aplicados ?s imagens. Assim, essa abordagem traz benef?cios significativos ao usu?rio, incluindo o aumento da produtividade, efici?ncia, redu??o de custos e tempo de desenvolvimento visto que ele se mant?m em sua especialidade. Esse software e sua implementa??o ser?o apresentados neste trabalho de conclus?o de curso

Evenness mediates the global relationship between forest productivity and richness

1. Biodiversity is an important component of natural ecosystems, with higher species richness often correlating with an increase in ecosystem productivity. Yet, this relationship varies substantially across environments, typically becoming less pronounced at high levels of species richness. However, species richness alone cannot reflect all important properties of a community, including community evenness, which may mediate the relationship between biodiversity and productivity. If the evenness of a community correlates negatively with richness across forests globally, then a greater number of species may not always increase overall diversity and productivity of the system. Theoretical work and local empirical studies have shown that the effect of evenness on ecosystem functioning may be especially strong at high richness levels, yet the consistency of this remains untested at a global scale. 2. Here, we used a dataset of forests from across the globe, which includes composition, biomass accumulation and net primary productivity, to explore whether productivity correlates with community evenness and richness in a way that evenness appears to buffer the effect of richness. Specifically, we evaluated whether low levels of evenness in speciose communities correlate with the attenuation of the richness–productivity relationship. 3. We found that tree species richness and evenness are negatively correlated across forests globally, with highly speciose forests typically comprising a few dominant and many rare species. Furthermore, we found that the correlation between diversity and productivity changes with evenness: at low richness, uneven communities are more productive, while at high richness, even communities are more productive. 4. Synthesis. Collectively, these results demonstrate that evenness is an integral component of the relationship between biodiversity and productivity, and that the attenuating effect of richness on forest productivity might be partly explained by low evenness in speciose communities. Productivity generally increases with species richness, until reduced evenness limits the overall increases in community diversity. Our research suggests that evenness is a fundamental component of biodiversity–ecosystem function relationships, and is of critical importance for guiding conservation and sustainable ecosystem management decisions

Native diversity buffers against severity of non-native tree invasions

Determining the drivers of non-native plant invasions is critical for managing native ecosystems and limiting the spread of invasive species$^{1,2}$. Tree invasions in particular have been relatively overlooked, even though they have the potential to transform ecosystems and economies$^{3,4}$. Here, leveraging global tree databases$^{5,6,7}$, we explore how the phylogenetic and functional diversity of native tree communities, human pressure and the environment influence the establishment of non-native tree species and the subsequent invasion severity. We find that anthropogenic factors are key to predicting whether a location is invaded, but that invasion severity is underpinned by native diversity, with higher diversity predicting lower invasion severity. Temperature and precipitation emerge as strong predictors of invasion strategy, with non-native species invading successfully when they are similar to the native community in cold or dry extremes. Yet, despite the influence of these ecological forces in determining invasion strategy, we find evidence that these patterns can be obscured by human activity, with lower ecological signal in areas with higher proximity to shipping ports. Our global perspective of non-native tree invasion highlights that human drivers influence non-native tree presence, and that native phylogenetic and functional diversity have a critical role in the establishment and spread of subsequent invasions

The global biogeography of tree leaf form and habit

Understanding what controls global leaf type variation in trees is crucial for comprehending their role in terrestrial ecosystems, including carbon, water and nutrient dynamics. Yet our understanding of the factors influencing forest leaf types remains incomplete, leaving us uncertain about the global proportions of needle-leaved, broadleaved, evergreen and deciduous trees. To address these gaps, we conducted a global, ground-sourced assessment of forest leaf-type variation by integrating forest inventory data with comprehensive leaf form (broadleaf vs needle-leaf) and habit (evergreen vs deciduous) records. We found that global variation in leaf habit is primarily driven by isothermality and soil characteristics, while leaf form is predominantly driven by temperature. Given these relationships, we estimate that 38% of global tree individuals are needle-leaved evergreen, 29% are broadleaved evergreen, 27% are broadleaved deciduous and 5% are needle-leaved deciduous. The aboveground biomass distribution among these tree types is approximately 21% (126.4 Gt), 54% (335.7 Gt), 22% (136.2 Gt) and 3% (18.7 Gt), respectively. We further project that, depending on future emissions pathways, 17-34% of forested areas will experience climate conditions by the end of the century that currently support a different forest type, highlighting the intensification of climatic stress on existing forests. By quantifying the distribution of tree leaf types and their corresponding biomass, and identifying regions where climate change will exert greatest pressure on current leaf types, our results can help improve predictions of future terrestrial ecosystem functioning and carbon cycling

The global biogeography of tree leaf form and habit.

Understanding what controls global leaf type variation in trees is crucial for comprehending their role in terrestrial ecosystems, including carbon, water and nutrient dynamics. Yet our understanding of the factors influencing forest leaf types remains incomplete, leaving us uncertain about the global proportions of needle-leaved, broadleaved, evergreen and deciduous trees. To address these gaps, we conducted a global, ground-sourced assessment of forest leaf-type variation by integrating forest inventory data with comprehensive leaf form (broadleaf vs needle-leaf) and habit (evergreen vs deciduous) records. We found that global variation in leaf habit is primarily driven by isothermality and soil characteristics, while leaf form is predominantly driven by temperature. Given these relationships, we estimate that 38% of global tree individuals are needle-leaved evergreen, 29% are broadleaved evergreen, 27% are broadleaved deciduous and 5% are needle-leaved deciduous. The aboveground biomass distribution among these tree types is approximately 21% (126.4 Gt), 54% (335.7 Gt), 22% (136.2 Gt) and 3% (18.7 Gt), respectively. We further project that, depending on future emissions pathways, 17-34% of forested areas will experience climate conditions by the end of the century that currently support a different forest type, highlighting the intensification of climatic stress on existing forests. By quantifying the distribution of tree leaf types and their corresponding biomass, and identifying regions where climate change will exert greatest pressure on current leaf types, our results can help improve predictions of future terrestrial ecosystem functioning and carbon cycling

Native diversity buffers against severity of non-native tree invasions.

Determining the drivers of non-native plant invasions is critical for managing native ecosystems and limiting the spread of invasive species1,2. Tree invasions in particular have been relatively overlooked, even though they have the potential to transform ecosystems and economies3,4. Here, leveraging global tree databases5-7, we explore how the phylogenetic and functional diversity of native tree communities, human pressure and the environment influence the establishment of non-native tree species and the subsequent invasion severity. We find that anthropogenic factors are key to predicting whether a location is invaded, but that invasion severity is underpinned by native diversity, with higher diversity predicting lower invasion severity. Temperature and precipitation emerge as strong predictors of invasion strategy, with non-native species invading successfully when they are similar to the native community in cold or dry extremes. Yet, despite the influence of these ecological forces in determining invasion strategy, we find evidence that these patterns can be obscured by human activity, with lower ecological signal in areas with higher proximity to shipping ports. Our global perspective of non-native tree invasion highlights that human drivers influence non-native tree presence, and that native phylogenetic and functional diversity have a critical role in the establishment and spread of subsequent invasions

Native diversity buffers against severity of non-native tree invasions

Determining the drivers of non-native plant invasions is critical for managing native ecosystems and limiting the spread of invasive species1,2. Tree invasions in particular have been relatively overlooked, even though they have the potential to transform ecosystems and economies3,4. Here, leveraging global tree databases5-7, we explore how the phylogenetic and functional diversity of native tree communities, human pressure and the environment influence the establishment of non-native tree species and the subsequent invasion severity. We find that anthropogenic factors are key to predicting whether a location is invaded, but that invasion severity is underpinned by native diversity, with higher diversity predicting lower invasion severity. Temperature and precipitation emerge as strong predictors of invasion strategy, with non-native species invading successfully when they are similar to the native community in cold or dry extremes. Yet, despite the influence of these ecological forces in determining invasion strategy, we find evidence that these patterns can be obscured by human activity, with lower ecological signal in areas with higher proximity to shipping ports. Our global perspective of non-native tree invasion highlights that human drivers influence non-native tree presence, and that native phylogenetic and functional diversity have a critical role in the establishment and spread of subsequent invasions

Evenness mediates the global relationship between forest productivity and richness

1. Biodiversity is an important component of natural ecosystems, with higher species richness often correlating with an increase in ecosystem productivity. Yet, this relationship varies substantially across environments, typically becoming less pronounced at high levels of species richness. However, species richness alone cannot reflect all important properties of a community, including community evenness, which may mediate the relationship between biodiversity and productivity. If the evenness of a community correlates negatively with richness across forests globally, then a greater number of species may not always increase overall diversity and productivity of the system. Theoretical work and local empirical studies have shown that the effect of evenness on ecosystem functioning may be especially strong at high richness levels, yet the consistency of this remains untested at a global scale. 2. Here, we used a dataset of forests from across the globe, which includes composition, biomass accumulation and net primary productivity, to explore whether productivity correlates with community evenness and richness in a way that evenness appears to buffer the effect of richness. Specifically, we evaluated whether low levels of evenness in speciose communities correlate with the attenuation of the richness–productivity relationship. 3. We found that tree species richness and evenness are negatively correlated across forests globally, with highly speciose forests typically comprising a few dominant and many rare species. Furthermore, we found that the correlation between diversity and productivity changes with evenness: at low richness, uneven communities are more productive, while at high richness, even communities are more productive. 4. Synthesis. Collectively, these results demonstrate that evenness is an integral component of the relationship between biodiversity and productivity, and that the attenuating effect of richness on forest productivity might be partly explained by low evenness in speciose communities. Productivity generally increases with species richness, until reduced evenness limits the overall increases in community diversity. Our research suggests that evenness is a fundamental component of biodiversity–ecosystem function relationships, and is of critical importance for guiding conservation and sustainable ecosystem management decisions