The impact behavior of composite materials has been extensively studied but interest has been cen... more The impact behavior of composite materials has been extensively studied but interest has been centered on flat plates. For underwater applications, thick composite cylinders are employed and several questions must be addressed concerning the influence of accidental impact. The aim of this work is to study the dynamic response of tubular structures. Such structures find many applications but the damage upon impact is not taken into account during their dimensioning. However, at the time of their handling or in service the damage introduced by accidental impact can compromise their capacity to fulfill their function. The cylinders are thick and consist of epoxy matrix and glass fiber reinforcement. After having observed the nature of the damage related to the static and dynamic loading, the scale and size effects on dynamic response and damage are examined. The studies reveal that the dynamic responses show a satisfactory correlation with predictions based on rules of similitude.
This paper presents experimental and analytical investigation on drilling of carbon fibre reinfor... more This paper presents experimental and analytical investigation on drilling of carbon fibre reinforced plastic and aluminium stacks. The experimental results conducted as per full factorial experimental design reveal that drill diameter and feed rate have significant effects in reducing thrust force and torque while spindle speed has the least effect. The analytical study is based on artificial neural network (ANN) training using feed-forward back propagation network. The correlations obtained by multi-variable regression analysis and ANN, indicate that ANN is more effective than regression analysis.
Ligação à página Inicial, This Page in English Saltar para: Menu Principal, Conteúdo, Opções, Log... more Ligação à página Inicial, This Page in English Saltar para: Menu Principal, Conteúdo, Opções, Login, Atalhos. Ajuda Contextual, Autenticar-se. FEUP Mobility Network. Você está em: Início > Investigação e Desenvolvimento > Publicações > Visualização. ...
A technological specimen, representative of industrial structural elements, was developed in orde... more A technological specimen, representative of industrial structural elements, was developed in order to analyze the material properties existing within the structure [1]. The specimen is of beam type and presents design singularities such as important thicknesses, ply drop off zones and a reinforced zone. The present study concerns the central reinforced zone of the specimen where several optical fiber Bragg grating sensors (FBG) have been embedded and spread through-the-thickness. The first step concerns the autoclave cure monitoring of the carbonepoxy (Hexply M21 T700GC) technological specimen obtained thanks to the FBG's [2, 3, 4]. In a second step, the technological specimen is submitted to 3 and 4-point bending tests in order to estimate strain distribution during solicitations obtained with both FBG [5] and 3D digital image correlation (3D-DIC). A test-calculation dialogue is then developed [6].
Drilling of multimaterails is a challenge to manufacturing engineers. Many combinations of multim... more Drilling of multimaterails is a challenge to manufacturing engineers. Many combinations of multimaterial stacks are possible, they are CFRP/Ti, CFRP/Al, CFRP/Ti/Al etc. The thrust force and surface roughness measured during drilling using plain carbide drill (K20) with drill parameters in drilling carbon fibre reinforced plastic (CFRP) laminate/aluminium (Grade 2024) stack and CFRP/Ti were experimentally investigated in this study.
In this paper, the Multi-Instrumented Technological Evaluator (MITE) is presented as an alternati... more In this paper, the Multi-Instrumented Technological Evaluator (MITE) is presented as an alternative approach to study the mechanical performance of composite structures. The goal is to have an enrichment of the calculus-testing dialogue by means of the interaction of four complementary divisions: the composite structure, the multi-axial testing machine, the numerical models and the multi-sensor instrumentation. As a first proposition, the MITE suggests the testing of a M10CHS300 carbon-epoxy composite plate with two drop-offs under combined loads. The study of drop-offs zones concerns several industries, such as aeronautics, maritime and automotive. A multi-axial testing machine, of four degrees of freedom was designed in order to recreate at the best, multiple load configurations which are more realistic than the conventional mechanics tests.The load configuration to be applied to the composite plate is torsion-bending. The kinematics of the testing machine and the proper load-mome...
Regardless of the high ‘strength to mass’ ratio, specially for parts made of carbon fiber reinfor... more Regardless of the high ‘strength to mass’ ratio, specially for parts made of carbon fiber reinforcements, the reduction in terms of mass as well as in terms of cost of a composite aircraft structure are below than those expected. One of the challenges that restrain the optimal use of composites in an aircraft structures is the difficulty to deal with the inherent variability of composite materials, in particular in the structural features (structural singularity). Since the structural elements are fabricated using complex multi-step processing, each one of these steps add their own set of variabilities towards the final composite structure. The treatment of these variabilities is still not very well included into the analytical prediction of the behavior of a composite structure. The main goal of this work is to expand a material’s property database, which includes these variabilities, to be used in conjunction with the hypothesis made in the analytical prediction of the structural ...
Abstract In this paper, the Multi-Instrumented Technological Evaluator (MITE) is presented as an ... more Abstract In this paper, the Multi-Instrumented Technological Evaluator (MITE) is presented as an alternative approach to study the mechanical performance of composite structures with singularity details. The goal is to have an enrichment of the calculation/test correlation by means of the interaction of four complementary aspects: the composite structure, the multi-axial testing machine, the numerical models and the multi-sensor instrumentation. As a first plan, the MITE suggests the testing of a carbon–epoxy composite plate with two drop-offs under combined loads. By means of Finite Element models (FE-models), the kinematics of the testing machine is applied to the composite plate to have a first numerical approach of its behaviour. Then, the experimental campaign is accomplished with multi-instrumentation devices and techniques such as strain gauges and Digital Image Correlation (DIC). The strain values calculated by FE-model and the experimental strain data acquired by gauges and DIC are confronted in order to understand the main fracture mechanisms acting on the drop-off zones, to determine the accuracy of the measurements techniques and to assure that a correct calculation/test correlation is achieved.
The impact behavior of composite materials has been extensively studied but interest has been cen... more The impact behavior of composite materials has been extensively studied but interest has been centered on flat plates. For underwater applications, thick composite cylinders are employed and several questions must be addressed concerning the influence of accidental impact. The aim of this work is to study the dynamic response of tubular structures. Such structures find many applications but the damage upon impact is not taken into account during their dimensioning. However, at the time of their handling or in service the damage introduced by accidental impact can compromise their capacity to fulfill their function. The cylinders are thick and consist of epoxy matrix and glass fiber reinforcement. After having observed the nature of the damage related to the static and dynamic loading, the scale and size effects on dynamic response and damage are examined. The studies reveal that the dynamic responses show a satisfactory correlation with predictions based on rules of similitude.
This paper presents experimental and analytical investigation on drilling of carbon fibre reinfor... more This paper presents experimental and analytical investigation on drilling of carbon fibre reinforced plastic and aluminium stacks. The experimental results conducted as per full factorial experimental design reveal that drill diameter and feed rate have significant effects in reducing thrust force and torque while spindle speed has the least effect. The analytical study is based on artificial neural network (ANN) training using feed-forward back propagation network. The correlations obtained by multi-variable regression analysis and ANN, indicate that ANN is more effective than regression analysis.
Ligação à página Inicial, This Page in English Saltar para: Menu Principal, Conteúdo, Opções, Log... more Ligação à página Inicial, This Page in English Saltar para: Menu Principal, Conteúdo, Opções, Login, Atalhos. Ajuda Contextual, Autenticar-se. FEUP Mobility Network. Você está em: Início > Investigação e Desenvolvimento > Publicações > Visualização. ...
A technological specimen, representative of industrial structural elements, was developed in orde... more A technological specimen, representative of industrial structural elements, was developed in order to analyze the material properties existing within the structure [1]. The specimen is of beam type and presents design singularities such as important thicknesses, ply drop off zones and a reinforced zone. The present study concerns the central reinforced zone of the specimen where several optical fiber Bragg grating sensors (FBG) have been embedded and spread through-the-thickness. The first step concerns the autoclave cure monitoring of the carbonepoxy (Hexply M21 T700GC) technological specimen obtained thanks to the FBG's [2, 3, 4]. In a second step, the technological specimen is submitted to 3 and 4-point bending tests in order to estimate strain distribution during solicitations obtained with both FBG [5] and 3D digital image correlation (3D-DIC). A test-calculation dialogue is then developed [6].
Drilling of multimaterails is a challenge to manufacturing engineers. Many combinations of multim... more Drilling of multimaterails is a challenge to manufacturing engineers. Many combinations of multimaterial stacks are possible, they are CFRP/Ti, CFRP/Al, CFRP/Ti/Al etc. The thrust force and surface roughness measured during drilling using plain carbide drill (K20) with drill parameters in drilling carbon fibre reinforced plastic (CFRP) laminate/aluminium (Grade 2024) stack and CFRP/Ti were experimentally investigated in this study.
In this paper, the Multi-Instrumented Technological Evaluator (MITE) is presented as an alternati... more In this paper, the Multi-Instrumented Technological Evaluator (MITE) is presented as an alternative approach to study the mechanical performance of composite structures. The goal is to have an enrichment of the calculus-testing dialogue by means of the interaction of four complementary divisions: the composite structure, the multi-axial testing machine, the numerical models and the multi-sensor instrumentation. As a first proposition, the MITE suggests the testing of a M10CHS300 carbon-epoxy composite plate with two drop-offs under combined loads. The study of drop-offs zones concerns several industries, such as aeronautics, maritime and automotive. A multi-axial testing machine, of four degrees of freedom was designed in order to recreate at the best, multiple load configurations which are more realistic than the conventional mechanics tests.The load configuration to be applied to the composite plate is torsion-bending. The kinematics of the testing machine and the proper load-mome...
Regardless of the high ‘strength to mass’ ratio, specially for parts made of carbon fiber reinfor... more Regardless of the high ‘strength to mass’ ratio, specially for parts made of carbon fiber reinforcements, the reduction in terms of mass as well as in terms of cost of a composite aircraft structure are below than those expected. One of the challenges that restrain the optimal use of composites in an aircraft structures is the difficulty to deal with the inherent variability of composite materials, in particular in the structural features (structural singularity). Since the structural elements are fabricated using complex multi-step processing, each one of these steps add their own set of variabilities towards the final composite structure. The treatment of these variabilities is still not very well included into the analytical prediction of the behavior of a composite structure. The main goal of this work is to expand a material’s property database, which includes these variabilities, to be used in conjunction with the hypothesis made in the analytical prediction of the structural ...
Abstract In this paper, the Multi-Instrumented Technological Evaluator (MITE) is presented as an ... more Abstract In this paper, the Multi-Instrumented Technological Evaluator (MITE) is presented as an alternative approach to study the mechanical performance of composite structures with singularity details. The goal is to have an enrichment of the calculation/test correlation by means of the interaction of four complementary aspects: the composite structure, the multi-axial testing machine, the numerical models and the multi-sensor instrumentation. As a first plan, the MITE suggests the testing of a carbon–epoxy composite plate with two drop-offs under combined loads. By means of Finite Element models (FE-models), the kinematics of the testing machine is applied to the composite plate to have a first numerical approach of its behaviour. Then, the experimental campaign is accomplished with multi-instrumentation devices and techniques such as strain gauges and Digital Image Correlation (DIC). The strain values calculated by FE-model and the experimental strain data acquired by gauges and DIC are confronted in order to understand the main fracture mechanisms acting on the drop-off zones, to determine the accuracy of the measurements techniques and to assure that a correct calculation/test correlation is achieved.
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