Mechanical Characterisation of Pneumatically-Spliced Carbon Fibre Yarns as Reinforcements for Polymer Composites

An investigation into the mechanical response of pneumatically-spliced carbon fibre yarns as a potential reinforcing material for polymer composites is presented. High strength mechanical connections between carbon fibre yarns are produced by joining short discontinuous tows into longer lengths via fibre entanglement. The effect of altering the number of high-pressure air pulses fired by a commercially available (Airbond 701H) splicing machine, to form the tow-tow connection, on load bearing capacity and linear stiffness is first evaluated on splices between virgin T700SC-24K-50C carbon fibre tows. The best performing spliced configuration is subsequently utilised in reinforcing unidirectional epoxy laminates, which are mechanically characterised, and their properties compared to those of various continuous fibre and chopped strand mat panels. Results presented in this study demonstrate that pneumatic splicing provides a high strength and sustainable solution for reinforcing polymers with discontinuous (approx. >50 mm in length) virgin, off-cut or waste carbon fibre yarns. It is speculated that with further research, quasi-continuous yarns remanufactured by splicing waste fibres could provide a novel material for weaving, braiding, non-crimp fabrics, or use in 3D printing applications

Oxygen consumption and rate of perceived exertion at different rhythms in water aerobics

O objetivo do estudo foi correlacionar o consumo de oxigênio (VO2) e o percentual do VO2 máximo (%VO2máx) com o índice de esforço percebido (IEP) e comparar essas variáveis entre exercícios de hidroginástica executados no meio aquático em diferentes ritmos de execução. Seis mulheres realizaram quatro sessões de testes, uma no meio terrestre (teste de esforço máximo) e três no meio aquático, cada uma com a execução de um exercício de hidroginástica: corrida estacionária, deslize lateral e chute frontal até 45. Cada exercício aquático foi realizado em três ritmos de execução, 80, 100 e 120bpm, durante 6 min (intervalo de 30 min). Para todas as variáveis, não foram observadas diferenças significativas entre os três exercícios, todavia, as mesmas apresentaram diferenças significativas entre os ritmos, indicando que com o aumento do ritmo, o esforço para executar os exercícios foi intensificado. Correlações significativas foram observadas entre VO2 e IEP e entre %VO2máx e IEP. Logo, baseado nessas associações, sugere-se que a prescrição da intensidade dos exercícios analisados possa ser feita através do IEP durante aulas de hidroginástica.The purpose of the study was to correlate the oxygen consumption (VO2) and the percentage of maximal VO2 (%VO2max) with the rate of perceived exertion (RPE) and to compare these variable between water aerobic exercises performed in aquatic environment at different rhythms. Six women performed four test sessions, one on dry land environment (maximal effort test) and three in aquatic environment, each one with the performance of a water aerobic exercise: stationary running, jumping jacks and frontal kick up to 45. Each aquatic exercise was performed at three rhythms of execution, 80, 100 and 120 bpm, during 6 min (interval of 30 min). For all variables, no significant differences were observed between three exercises, however, significant differences were found between rhythms of execution for all of them, indicating that with the increase of the rhythm, the effort to perform the exercises was intensified. Significant correlations were observed between VO2 and RPE, and between %VO2max and RPE. Therefore, based on this association it is suggested that the prescription of intensity of the exercises analyzed can be done by RPE during water aerobic classes

Comparação das cargas internas impostas à coluna vertebral com diferentes intensidades de carga no exercício de força stiff

Introdução: na área da biomecânica, diversos estudos demonstram a importância de entender as forças e momentos internos que ocorrem no corpo humano durante a prática das atividades da vida diária (AVDs) e a prática esportiva como em exercícios de força. Objetivo: comparar forças musculares (FM) e articulares (FA) impostas em três segmentos da coluna vertebral, por meio do macromodelo biomecânico tridimensional (MM3D), durante a realização do exercício stiff, com diferentes intensidades de carga. Metodologia: cinco indivíduos saudáveis, com 21,6±1.5anos, 173.1±7.8cm e 68±7,3kg realizaram 5 repetições dos exercícios stiff, com 25%1RM, 50%1RM e 75%1RM. Durante a coleta de dados foram adquiridos dados de cinemetria 3D, utilizados como variáveis de entrada juntamente com os parâmetros antropométricos no MM3D, o qual baseado nas técnicas da dinâmica inversa e de otimização fornece as forças articular e muscular resultantes em três regiões da coluna vertebral: tronco superior (C7/T1), tronco médio (T8/T9) e tronco inferior (L5/S1). Resultados: não foram encontradas diferenças entre as três cargas selecionadas para os valores de FM e FA nos três níveis da coluna. Em adição, FM e FA normalizados em relação à carga externa apresentaram diferenças significativas entre as cargas 25%1RM e 75%1RM, nos troncos médio e inferior. Conclusão: Os resultados demonstraram que, à medida que a carga externa aumenta, nem sempre FM e FA impostas nos segmentos da coluna vertebral aumentam. Entretanto, para uma mesma carga, quanto mais baixo o nível do tronco, maiores os valores de FM e FA.Introduction: in biomechanics, several studies demonstrate the importance of understanding the internal forces and moments during Activities of daily Living (ADL) or in sports, as well as resistance exercises, were found. Objective: The purpose of this study was to compare muscle and joint forces imposed by three segments of the trunk with a tridimensional biomechanical macromodel of the spine (MM3D) during stiff, a resistance exercise, at different intensities. Methodology: five healthy subjects, 21,6±1.5years old, 173.1±7.8cm e 68±7,3kg, performed five repetitions of stiff in 25%1MR, 50%1MR and 75%1MR. Kinematic 3D data and were collected during the session, which were used as input with anthropometric parameters on MM3D. This model provides resultant muscle and joint forces through inverse dynamic and optimization techniques. MM3D provide data about three lands of spine: superior (C7/T1), medium (T8/T9) and inferior (L5/S1). Results: There were not found significant differences on absolut values of resultant muscle and joint forces between three intensities performed. In addition, there were found significant differences between 25%1MR and 75%1MR, on medium and inferior trunk, when the muscle and joint forces were normalized by the intensity of the exercise. Conclusion: The results showed that muscle and joint forces didn’t have a relation direct with the intensity of the exercise. Whoever, at the same intensity, as less as the level of the trunk, it’s bigger the values of muscle and joint forces

Comparação das cargas internas impostas à coluna vertebral com diferentes intensidades de carga no exercício de força stiff

Introdução: na área da biomecânica, diversos estudos demonstram a importância de entender as forças e momentos internos que ocorrem no corpo humano durante a prática das atividades da vida diária (AVDs) e a prática esportiva como em exercícios de força. Objetivo: comparar forças musculares (FM) e articulares (FA) impostas em três segmentos da coluna vertebral, por meio do macromodelo biomecânico tridimensional (MM3D), durante a realização do exercício stiff, com diferentes intensidades de carga. Metodologia: cinco indivíduos saudáveis, com 21,6±1.5anos, 173.1±7.8cm e 68±7,3kg realizaram 5 repetições dos exercícios stiff, com 25%1RM, 50%1RM e 75%1RM. Durante a coleta de dados foram adquiridos dados de cinemetria 3D, utilizados como variáveis de entrada juntamente com os parâmetros antropométricos no MM3D, o qual baseado nas técnicas da dinâmica inversa e de otimização fornece as forças articular e muscular resultantes em três regiões da coluna vertebral: tronco superior (C7/T1), tronco médio (T8/T9) e tronco inferior (L5/S1). Resultados: não foram encontradas diferenças entre as três cargas selecionadas para os valores de FM e FA nos três níveis da coluna. Em adição, FM e FA normalizados em relação à carga externa apresentaram diferenças significativas entre as cargas 25%1RM e 75%1RM, nos troncos médio e inferior. Conclusão: Os resultados demonstraram que, à medida que a carga externa aumenta, nem sempre FM e FA impostas nos segmentos da coluna vertebral aumentam. Entretanto, para uma mesma carga, quanto mais baixo o nível do tronco, maiores os valores de FM e FA.Introduction: in biomechanics, several studies demonstrate the importance of understanding the internal forces and moments during Activities of daily Living (ADL) or in sports, as well as resistance exercises, were found. Objective: The purpose of this study was to compare muscle and joint forces imposed by three segments of the trunk with a tridimensional biomechanical macromodel of the spine (MM3D) during stiff, a resistance exercise, at different intensities. Methodology: five healthy subjects, 21,6±1.5years old, 173.1±7.8cm e 68±7,3kg, performed five repetitions of stiff in 25%1MR, 50%1MR and 75%1MR. Kinematic 3D data and were collected during the session, which were used as input with anthropometric parameters on MM3D. This model provides resultant muscle and joint forces through inverse dynamic and optimization techniques. MM3D provide data about three lands of spine: superior (C7/T1), medium (T8/T9) and inferior (L5/S1). Results: There were not found significant differences on absolut values of resultant muscle and joint forces between three intensities performed. In addition, there were found significant differences between 25%1MR and 75%1MR, on medium and inferior trunk, when the muscle and joint forces were normalized by the intensity of the exercise. Conclusion: The results showed that muscle and joint forces didn’t have a relation direct with the intensity of the exercise. Whoever, at the same intensity, as less as the level of the trunk, it’s bigger the values of muscle and joint forces

Oxygen consumption and rate of perceived exertion at different rhythms in water aerobics

O objetivo do estudo foi correlacionar o consumo de oxigênio (VO2) e o percentual do VO2 máximo (%VO2máx) com o índice de esforço percebido (IEP) e comparar essas variáveis entre exercícios de hidroginástica executados no meio aquático em diferentes ritmos de execução. Seis mulheres realizaram quatro sessões de testes, uma no meio terrestre (teste de esforço máximo) e três no meio aquático, cada uma com a execução de um exercício de hidroginástica: corrida estacionária, deslize lateral e chute frontal até 45. Cada exercício aquático foi realizado em três ritmos de execução, 80, 100 e 120bpm, durante 6 min (intervalo de 30 min). Para todas as variáveis, não foram observadas diferenças significativas entre os três exercícios, todavia, as mesmas apresentaram diferenças significativas entre os ritmos, indicando que com o aumento do ritmo, o esforço para executar os exercícios foi intensificado. Correlações significativas foram observadas entre VO2 e IEP e entre %VO2máx e IEP. Logo, baseado nessas associações, sugere-se que a prescrição da intensidade dos exercícios analisados possa ser feita através do IEP durante aulas de hidroginástica.The purpose of the study was to correlate the oxygen consumption (VO2) and the percentage of maximal VO2 (%VO2max) with the rate of perceived exertion (RPE) and to compare these variable between water aerobic exercises performed in aquatic environment at different rhythms. Six women performed four test sessions, one on dry land environment (maximal effort test) and three in aquatic environment, each one with the performance of a water aerobic exercise: stationary running, jumping jacks and frontal kick up to 45. Each aquatic exercise was performed at three rhythms of execution, 80, 100 and 120 bpm, during 6 min (interval of 30 min). For all variables, no significant differences were observed between three exercises, however, significant differences were found between rhythms of execution for all of them, indicating that with the increase of the rhythm, the effort to perform the exercises was intensified. Significant correlations were observed between VO2 and RPE, and between %VO2max and RPE. Therefore, based on this association it is suggested that the prescription of intensity of the exercises analyzed can be done by RPE during water aerobic classes