In this investigation, we assess the use of pine resin and flax fibre as raw materials for the formulation of a biocomposite material to determine its applicability and demonstrate the hidden potential that may presently be underexploited... more
In this investigation, we assess the use of pine resin and flax fibre as raw materials for the formulation of a biocomposite material to determine its applicability and demonstrate the hidden potential that may presently be underexploited with these two resources. The formulated biocomposite was subjected to bending tests, comparing reinforced and non-reinforced matrices with flax fibre. Different additives of natural and synthetic origin were used to improve the fragility of the rosin, with EVA (ethylene vinyl acetate) being the material that presented greater potential, in the proportion of 30%. This formulation was used to manufacture innovative products. The results obtained are very promising and opens the opportunity to design and manufacture new sustainable products that can be used in different industrial areas, like furniture and lighting. The products hereby introduced envision to contribute for the rehabilitation of the rosin industry and revive the flax culture in Portugal.
Research Interests:
Reinforced thermoplastic and thermosetting matrix pipes, produced by filament winding or centrifugal casting, may be subjected to different types of loading conditions as well as different environmental conditions. However, they may... more
Reinforced thermoplastic and thermosetting matrix pipes, produced by filament winding or centrifugal casting, may be subjected to different types of loading conditions as well as different environmental conditions. However, they may suffer damage due to unexpected working conditions (low velocity impact, such as stones, tools, etc). This paper describes a methodology based upon fracture mechanics to evaluate possible pipe damages. It reports a set of tests made to characterize materials and pipes. Fracture Mechanics tests were made in filament wound flat samples and tubular specimens were also subjected to low velocity impact tests. The study of damage evolution was done by using the ESPI (Electronic Speckle Pattern Interferometry) technique in order to determine the delamination area.
Research Interests: Materials Engineering, Materials Science, Materials, Image Processing and Analysis, Fiber Reinforced Plastic, and 11 moreInterest Groups, Damage, Manufacturing Engineering, Drilling, Delamination, Composite Material, Glass Fiber, New materials and manufacturing processes for aero engines, Carbon Fiber, Thrust Force, and Linear elastic fracture mechanics
Research Interests:
Research Interests:
Research Interests:
It has been difficult to improve the intramedullary nail technique because of the lack of consistency in the procedures used to evaluate the bone-implant stiffness. The goal of this study was to develop a simple methodology for... more
It has been difficult to improve the intramedullary nail technique because of the lack of consistency in the procedures used to evaluate the bone-implant stiffness. The goal of this study was to develop a simple methodology for determining the stiffness of a bone implant that considers the physiological loads and bone orientation, and allows a finite element analysis and its validation using mechanical experimentation. Finite element models for a composite tibia before and after an intramedullary nail was implanted were created and validated using the results of a set of mechanical experiments, in which the stiffness values of the model were measured and compared under axial compression, 4-point bending, shear, and torsional loads considering the patient’s condition in the early healing phase. Grips with personalized bone interfaces were developed to guarantee the physiological loads and bone orientation. In the 4-point bending, torsional, and shear loading modes, the developed bone-implant finite element model showed a satisfactory level of predictive potential in relation to the experimental observations, with a percentage variation of less than 35%. This study also demonstrated that despite the high stiffness of the bone-implant construct, motion was always generated at the interfragmentary site during the early healing phase. In addition, during this stage, the nail supported most of the load applied to the lower limb (up to 85%). This strategy could contribute to the future determination of the ideal mechanical environment at a fracture site and how this environment evolves throughout the healing process.
Research Interests:
Cost-effective glass-reinforced thermoplastic matrix towpregs produced by a powder coating line were used to manufacture composite pipes by filament winding. A conventional 6 axes filament-winding equipment was adapted for processing such... more
Cost-effective glass-reinforced thermoplastic matrix towpregs produced by a powder coating line were used to manufacture composite pipes by filament winding. A conventional 6 axes filament-winding equipment was adapted for processing such structures. The influence of the filament winding speed and mandrel temperature on the composite final properties was studied in the present work. An optimized processing window was established by comparing the composite theoretical expected mechanical properties with the experimentally obtained ones. The final properties determined on the produced pipes and structures and the technological changes introduced to the conventional filament-winding equipment will be presented and discussed. Besides the processing description and conditions, it will be presented the relationship between processing conditions and mechanical properties.
Research Interests:
The aim of this work is to optimize the production of new continuous carbon fibers reinforced thermoplastic matrix pre-impregnated materials (towpregs) continuously processed by dry deposition of polymer powders in a new equipment... more
The aim of this work is to optimize the production of new continuous carbon fibers reinforced thermoplastic matrix pre-impregnated materials (towpregs) continuously processed by dry deposition of polymer powders in a new equipment developed by the Institute for Polymers and Composites (IPC). The processing of the produced towpregs by pultrusion, in a developed prototype equipment existing in the Engineering School of the Polytechnic Institute of Porto (ISEP), was also optimized. Two different thermoplastic matrices were studied: one for commercial applications (polypropylene) and another for advanced markets (Primospire®). The optimization was made by studying the influence of the most relevant processing parameters in the final properties of the produced towpregs and composites. The final pultruded composite profiles were submitted to mechanical tests in order to obtain relevant properties.
Research Interests:
Historically, thermoset resins have dominated the composite industry but they start to be replaced by thermoplastics. In this study two different thermoplastic matrix carbon reinforced pre-impregnated materials were used, one produced in... more
Historically, thermoset resins have dominated the composite industry but they start to be replaced by thermoplastics. In this study two different thermoplastic matrix carbon reinforced pre-impregnated materials were used, one produced in our laboratories (towpreg) and another obtained from coextrusion process (PCT). Carbon fibre and two different thermoplastic matrices (polypropylene and PRIMOSPIRE) were selected for the production of the pre-impregnated materials. Heated compression moulding and pultrusion were the two manufacturing technologies used to obtain composite plates and profiles for study. The optimization of those processes was made by studying the influence of the most relevant processing parameters in the final properties of the produced carbon fibres thermoplastic matrix pre-impregnated materials and composites. The composite relevant mechanical properties were determined and the final composites were submitted to Dynamic Mechanical Analysis (DMA), Scanning Electron ...
Research Interests:
In this work, the stress and strain levels of composite overwrapped pressure vessels and composite tube were evaluated, through an accurate numerical modelling based on finite element method (FEM). It was developed the models of the COPV... more
In this work, the stress and strain levels of composite overwrapped pressure vessels and composite tube were evaluated, through an accurate numerical modelling based on finite element method (FEM). It was developed the models of the COPV and tubes with three aluminum liner thickness. Initially, the stress and displacement of the composite layers overwrapping the liner was analyzed and graphically represented. The parametric modelling for study the structural relationship between COPV and pipes were made by three new concepts developed in this work, liner stress and liner strain share fraction and thickness ratio. The results showed representative results at lower pressures, e.g. at 70 bar, where a composite tube can parametrically represent a COPV.
Research Interests:
Towpregs based on different fibres and thermoplastic matrices were processed for highly demanding and more commercial applications by different composite processing technologies. In the technologies used, compression moulding and... more
Towpregs based on different fibres and thermoplastic matrices were processed for highly demanding and more commercial applications by different composite processing technologies. In the technologies used, compression moulding and pultrusion, the final composite processing parameters were studied in order to obtain composites with adequate properties at industrial compatible production rates. The produced towpregs were tested to verify its polymer content and degree of impregnation. The obtained results have shown that the coating line enabled to produce, with efficiency and industrial scale speed rates, thermoplastic matrix towpregs that may be used to manufacture composites for advanced and larger volume commercial markets.
Research Interests:
Research Interests:
Abstract: This chapter presents the main processing techniques used with organic matrices fibrous materials reinforced composites, for civil engineering applications. After a brief introduction, followed by the characterization of the... more
Abstract: This chapter presents the main processing techniques used with organic matrices fibrous materials reinforced composites, for civil engineering applications. After a brief introduction, followed by the characterization of the main matrices, thermosets and thermoplastics used in these composites, the different techniques applied in various civil engineering applications are presented and discussed: pultrusion, braiding, RTM, filament winding, hot plate press and, finally, hand lay-up.
Research Interests:
Research Interests: Computer Science, Materials Science, Image Analysis, Image segmentation, Image Processing and Analysis, and 15 moreFiber Reinforced Plastic, Drilling, Key words, Epoxy, Delamination, Composite Material, Carrying Capacity, Bearing Capacity, Composite laminates, Radiografia, Análisis de imagen, Isotropy, Mechanical Property, Laminates, and Perforación
Given the unquestionable need of environmental preservation of discarded industrial residues, the scrape of tires, have been seen as a salutary alternative for addictive in concrete, asphalt production and of other composites materials.... more
Given the unquestionable need of environmental preservation of discarded industrial residues, the scrape of tires, have been seen as a salutary alternative for addictive in concrete, asphalt production and of other composites materials. In this work, grew a composite the base of scrape of tire as reinforcement and latex as matrix, to be used as insulating thermal…
Research Interests:
Research Interests:
Research Interests:
Research Interests:
The use of fibre reinforced plastics – FRP’s – in structures is under a considerable increase. Advantages of their use are related with their low weight, high strength and stiffness. The improvement of the dynamic characteristics has been... more
The use of fibre reinforced plastics – FRP’s – in structures is under a considerable increase. Advantages of their use are related with their low weight, high strength and stiffness. The improvement of the dynamic characteristics has been profitable for aeronautics, automobile, railway, naval and sporting goods industries. Drilling is a widely used machining technique as it is needed to assemble parts in a structure. This is a unique machining process, characterized by the existence of two different mechanisms: extrusion by the drill chisel edge and cutting by the rotating cutting lips. Drilling raises particular problems that can reduce mechanical and fatigue strength of the parts. In this work, quasi-isotropic hybrid laminates with 25% of carbon fibre reinforced plies and 4 mm thickness are produced, tested and drilled. Three different drill geometries are compared. Results considered are the interlaminar fracture toughness in Mode I – GIc –, thrust force during drilling and delam...
Research Interests:
The distinctive characteristics of carbon fibre reinforced plastics, like low weight or high specific strength, had broadened their use to new fields. Due to the need of assembly to structures, machining operations like drilling are... more
The distinctive characteristics of carbon fibre reinforced plastics, like low weight or high specific strength, had broadened their use to new fields. Due to the need of assembly to structures, machining operations like drilling are frequent. In result of composites inhomogeneity, this operation can lead to different damages that reduce mechanical strength of the parts in the connection area. From these damages, delamination is the most severe. A proper choice of tool and cutting parameters can reduce delamination substantially. In this work the results obtained with five different tool geometries are compared. Conclusions show that the choice of an adequate drill can reduce thrust forces, thus delamination damage.
Research Interests:
Research Interests:
The present work reports the development of new technologies to fabricate long and continuous-fiber-reinforced composite structures from low-cost thermoplastic matrix semiproducts. These semiproducts, thermoplastic matrix towpregs and... more
The present work reports the development of new technologies to fabricate long and continuous-fiber-reinforced composite structures from low-cost thermoplastic matrix semiproducts. These semiproducts, thermoplastic matrix towpregs and preconsolidated tapes (PCTs), were produced in a purposely-built prototype machine, by deposition of a thermoplastic polymer in powder form on continuous fibers. The work also presents the advances made in the processing of these materials into composites by conventional techniques, such as pultrusion, filament winding and compression molding. Finally, it describes the investigation of the optimal processing conditions that maximize the mechanical properties of the composites. These properties are good enough for the composites to be used as engineering materials in many structural applications.
Research Interests:
An interface finite element for three‐dimensional problems based on the penalty method is presented. The proposed element can model joints/interfaces between solid finite elements and also includes the propagation of damage in pure mode... more
An interface finite element for three‐dimensional problems based on the penalty method is presented. The proposed element can model joints/interfaces between solid finite elements and also includes the propagation of damage in pure mode I, pure mode II and mixed mode considering a softening relationship between the stresses and relative displacements. Two different contact conditions are considered: point‐to‐point constraint for closed points (not satisfying the failure criterion) and point‐to‐surface constraint for opened points. The performance of the element is tested under mode I, mode II and mixed mode loading conditions.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Low velocity impact damage can significantly reduce the residual strength of laminated composites. This kind of damage (mostly delaminations) is very dangerous for the structures because it is not apparent to the naked eye and, in some... more
Low velocity impact damage can significantly reduce the residual strength of laminated composites. This kind of damage (mostly delaminations) is very dangerous for the structures because it is not apparent to the naked eye and, in some cases, it can reduce the compressive residual strength up to 60%. In this work, a numerical model for predicting the compression failure of laminated composites containing delamination caused by low velocity impact was developed. An interface finite element, previously developed by the authors, was used. This element is compatible with twenty-seven node isoparametric hexahedral elements and enables modeling the behavior of the damaged interface, taking into account a three-dimensional stress state, the interpenetration constraint and the propagation of delamination. In order to verify the numerical model, some experimental work was done. The experimental work, performed on carbon-epoxy (04, 904)5 and (904, 04), laminates, included low velocity impact ...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
This paper reports an experimental study on the mode II interlaminar fracture of carbon/epoxy multidirectional laminates. A 3D finite element analysis was first performed to define appropriate stacking sequences for end-notched flexure... more
This paper reports an experimental study on the mode II interlaminar fracture of carbon/epoxy multidirectional laminates. A 3D finite element analysis was first performed to define appropriate stacking sequences for end-notched flexure (ENF) specimens with starter delaminations on θ/−θ and 0°/θ interfaces. The analysis concerned the shape of widthwise distributions of the mode II strain energy release rate, GII, the level of mode-mixity, the effect of residual stresses on GII and the applicability of data reduction schemes. The experimental GIIc values increased with the ply angle θ for both θ/−θ and 0°/θ specimens. These trends were found to be in agreement with an average interlaminar stress fracture criterion. However, this criterion proved to be of limited practical usefulness, as its predictions were dependent on a characteristic length. Therefore, GIIc measurements on multidirectional specimens remain essential for the application of accurate fracture mechanics based design cr...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
SUMMARY A framework composed of several building blocks that allows the simulation of the filament winding process is described. The physical and thermo-chemical phenomena interacting at the layer/laminate level together with analytical... more
SUMMARY A framework composed of several building blocks that allows the simulation of the filament winding process is described. The physical and thermo-chemical phenomena interacting at the layer/laminate level together with analytical description of the compaction and consolidation mechanisms were modelled and incorporated in finite element software. The filament winding process is a manufacturing technique in which a resin- impregnated
Research Interests:
ABSTRACT In this work, the load sharing ability of metallic liners in type III composite overwrapped pressure vessel (COPV) was investigated by means of accurate numerical models based on finite element method (FEM) in order to... more
ABSTRACT In this work, the load sharing ability of metallic liners in type III composite overwrapped pressure vessel (COPV) was investigated by means of accurate numerical models based on finite element method (FEM) in order to realistically represent the hybrid metal-composite structure. The varying thickness of the composite layers, as well as their angles throughout the dome surface, were accounted for in the model. The study focused on the influence of the material properties and the 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 COPV 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.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
... results for those speci-mens is somewhat questionable, as some nonlinear behaviour and small ... and Davies, P., 'Beam Analysis of Angle-ply Laminate End-notched Flexure Specimens', Composites ... Polaha, JJ, Davidson, BD,... more
... results for those speci-mens is somewhat questionable, as some nonlinear behaviour and small ... and Davies, P., 'Beam Analysis of Angle-ply Laminate End-notched Flexure Specimens', Composites ... Polaha, JJ, Davidson, BD, Hudson, RC, and Pieracci, A., 'Effects of Mode Ratio ...
Research Interests:
Research Interests:
The most popular and important biodegradable polymers are aliphatic polyesters, such as polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL), polyhydoxyalkanoates (PHA's) and polyethylene oxide... more
The most popular and important biodegradable polymers are aliphatic polyesters, such as polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL), polyhydoxyalkanoates (PHA's) and polyethylene oxide (PEO). However, each of these ...
Research Interests:
After a general discussion regarding different approaches towards sustainability with composite systems, several examples will be presented and discussed with respect to the design criteria for a given application. In fact, from the... more
After a general discussion regarding different approaches towards sustainability with composite systems, several examples will be presented and discussed with respect to the design criteria for a given application. In fact, from the mechanical characterization of PHA and PLA blends to the use of cork as a core in sandwich construction will aim for a larger incorporation of composite systems from renewable resources in structural applications and mass production.