Loading...
15 results
Search Results
Now showing 1 - 10 of 15
- Compression molding of pultruded carbon reinforced thermoplastic compositesPublication . Novo, P. J.; Nunes, J. P.; Silva, João F.; Marques, A. T.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 Microscope (SEM), optical microscopy and calcination tests. The determination of the fiber volume fraction of all studied composite was obtained comparing the results of thermogravimetric analysis (TGA), SEM and calcination tests.
- Processo de aglomeração de cortiça, em formas complexas, sem recurso a aglutinantes, por compressão a quentePublication . Martins, Fábio Miguel Cardoso; Silva, João F.A presente invenção tem aplicação direta na indústria corticeira e refere-se a Um processo de aglomeração de granulados de cortiça, provenientes de falcas, sem Recurso à adição de aglutinantes. São obtidas formas complexas, em série, utilizando Moldes que permitem conceber a forma final sem necessidade de qualquer operação de Acabamento, ou procedimentos adicionais de desbaste.os seus campos de aplicação são Variados, considerando as diversas utilizações dos aglomerados de cortiça. Contudo, a Maior parcela deverá corresponder a:- decoração ¿ peças decorativas de formas Complexas; - isolamentos ¿ peças de pequena e média dimensão para automóveis, indústria Aeroespacial, mecanismos de refrigeração ou caldeiraria.tendo em conta que o estado da Arte atual caracteriza-se pela aglomeração prévia em formas simples com posterior Maquinação na forma final pretendida, a obtenção de peças complexas recorrendo a um Procedimento com menor número de etapas e sem geração de desperdício, constitui a Grande evolução deste processo.
- Delamination analysis of carbon fibre reinforced laminates: evaluation of a special step drillPublication . Marques, A. T.; Durão, Luís M.; Magalhães, A. G.; Silva, João F.; Tavares, João Manuel R. S.Drilling of carbon fibre/epoxy laminates is usually carried out using standard drills. However, it is necessary to adapt the processes and/or tooling as the risk of delamination, or other damages, is high. These problems can affect mechanical properties of produced parts, therefore, lower reliability. In this paper, four different drills – three commercial and a special step (prototype) – are compared in terms of thrust force during drilling and delamination. In order to evaluate damage, enhanced radiography is applied. The resulting images were then computational processed using a previously developed image processing and analysis platform. Results show that the prototype drill had encouraging results in terms of maximum thrust force and delamination reduction. Furthermore, it is possible to state that a correct choice of drill geometry, particularly the use of a pilot hole, a conservative cutting speed – 53 m/min – and a low feed rate – 0.025 mm/rev – can help to prevent delamination.
- Pultrusion of fibre reinforced thermoplastic pre-impregnated materialsPublication . Novo, P.J.; Silva, João F.; Nunes, J.P.; Marques, A.T.Fibre reinforced thermoplastic pre-impregnated materials produced continuously by diverse methods and processing conditions were used to produce composites using pultrusion. The processing windows used to produce these materials and composites profiles were optimized by using the Taguchi/DOE (Design of Experiments) methods. Those composites were then submitted to mechanical testing and microscopy analysis. The obtained results were compared with the expected theoretical ones predicted from the Rule Of Mixtures (ROM) and with those of similar engineering conventional available materials. The results obtained shown that produced composites have adequate properties for applications in common and structural engineering markets.
- Producing LFT composite parts for large consumption markets from thermoplastic powder-coated towpregsPublication . Nunes, J. P.; Rodrigues, F. M.; Novo, P. J.; Silva, João F.Thermoplastic matrix composites are receiving increasing interest in last years. This is due to several advantageous properties and speed of processing of these materials as compared to their thermoset counterparts. Among thermoplastic composites, Long Fibre Thermoplastics (LFTs) have seen the fastest growth, mainly due to developments in the automotive sector [0, 2]. LFTs combine the (semi-)structural material properties of long (>1 cm) fibres, with the ease and speed of thermoplastic processing. This paper reports a study of a novel low-cost LFT technology and resulting composites. A patented powder-coating machine [3, 4] able to produce continuously pre-impregnated materials directly from fibre rovings and polymer powders was used to process glass-fibre reinforced polypropylene (GF/PP) towpregs. Such pre-impregnated materials were then chopped and used to make LFTs in a patented low-cost piston-blender developed by the Centre of Lightweight Structures, TUD-TNO, the Netherlands [5, 6]. The work allowed studying the most relevant towpreg production parameters and establishing the processing window needed to obtain a good quality GF/PP powder coated material. Finally, the processing window that allows producing LFTs of good quality in the piston-blender and the mechanical properties of final stamped GF/PP composite parts were also determined.
- Fracture toughness determination of adhesive and co-cured joints in natural fibre compositesPublication . Campilho, Raul; Moura, Daniel; Gonçalves, Daniel J. S.; Silva, João; Banea, Mariana D.; Silva, Lucas F. M. daAdhesive bonding has become more efficient in the last few decades due to the adhesives developments, granting higher strength and ductility. On the other hand, natural fibre composites have recently gained interest due to the low cost and density. It is therefore essential to predict the fracture behavior of joints between these materials, to assess the feasibility of joining or repairing with adhesives. In this work, the tensile fracture toughness (Gc n) of adhesive joints between natural fibre composites is studied, by bonding with a ductile adhesive and co-curing. Conventional methods to obtain Gc n are used for the co-cured specimens, while for the adhesive within the bonded joint, the J-integral is considered. For the J-integral calculation, an optical measurement method is developed for the evaluation of the crack tip opening and adherends rotation at the crack tip during the test, supported by a Matlab sub-routine for the automated extraction of these quantities. As output of this work, an optical method that allows an easier and quicker extraction of the parameters to obtain Gc n than the available methods is proposed (by the J-integral technique), and the fracture behaviour in tension of bonded and co-cured joints in jute-reinforced natural fibre composites is also provided for the subsequent strength prediction. Additionally, for the adhesively- bonded joints, the tensile cohesive law of the adhesive is derived by the direct method.
- Processing of carbon reinforced thermoplastic pre-impregnated materialsPublication . Novo, P. J.; Nunes, J. P.; Silva, João F.; Marques, A. T.The aim of this work is to produce and optimize the processing of carbon fibres thermoplastic matrix pre-impregnated materials (towpregs and PCT´s). Pultrusion and heated compression moulding were the selected manufacturing methods for processing all carbon fibres thermoplastic matrix pre-impregnated materials into composite parts. 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 method of Taguchi / DOE (Design of Experiments) was used to achieve this aim as it allowed making more rational choices of processing windows. The composite relevant mechanical properties were determined and studied. The final composites were also submitted to SEM microscopy analysis.
- Advanced Thermoplastic Carbon Fibre Reinforced Pultruded CompositesPublication . Novo, P. J.; Silva, João; Nunes, J. P.; Marques, A. T.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.
- Advances in thermoplastic pultruded compositesPublication . Novo, P. J.; Silva, João F.; Nunes, J. P.; Marques, A. T.Pultrusion is a versatile continuous high speed production technology allowing the production of fibre reinforced complex profiles. Thermosetting resins are normally used as matrices in the production of structural constant cross section profiles. Although only recently thermoplastic matrices have been used in long and continuous fibre reinforced composites replacing with success thermosetting matrices, the number of their applications is increasing due to their better ecological and mechanical performance. Composites with thermoplastic matrices offers increased fracture toughness, higher impact tolerance, short processing cycle time and excellent environmental stability. They are recyclable, post-formable and can be joined by welding. The use of long/continuous fibre reinforced thermoplastic matrix composites involves, however, great technological and scientific challenges since thermoplastics present much higher viscosity than thermosettings, which makes much difficult and complex the impregnation of reinforcements and consolidation tasks. [1] In this work continuous fibres reinforced thermoplastic matrix towpregs were produced using equipment developed by the Institute for Polymers and Composites (IPC). The processing of the towpregs was made by pultrusion, in a developed prototype equipment existing in the Engineering School of the Polytechnic Institute of Porto (ISEP). Different thermoplastic matrices and fibres raw-materials were used in this study to manufacture pultruded composites for commercial applications (glass and carbon fibre/ polypropylene) and for advanced markets (carbon fibre/Primospire®). To improve the temperature distribution profile in heating die, different modifications were performed. In order to optimize both processes, towpregs production and pultruded composites profiles were analysed to determine the influence of the most relevant processing parameters in the final properties. The final pultruded composite profiles were submitted to mechanical tests to obtain the relevant properties.
- Atas das 8as Jornadas de Segurança aos Incêndios Urbanos e as 3as Jornadas de Proteção Civil (8JORNINC-3JORPROCIV)Publication . Fonseca, Elza M M; Lopes, Hernâni M. L; Campos, Armando; João, Ana Maria Raposo; Magalhães, António Gonçalves; Silva, João F.Este livro de ATAS contém os artigos apresentados às 8as Jornadas de Segurança aos Incêndios Urbanos e às 3as Jornadas de Proteção Civil (8JORNINC-3JORPROCIV), que decorreram no Porto, Portugal. Na presente edição das 8JORNINC-3JORPROCIV foram submetidos 50 trabalhos, tendo sido aceites 42. Os trabalhos foram distribuídos em 8 sessões paralelas temáticas, em adição a 2 sessões plenárias, apresentados no dia 2 de junho de 2023. O evento foi iniciado e promovido em Portugal, sob a organização do professor Doutor João Paulo Rodrigues, com as 1as Jornadas de Segurança aos Incêndios Urbanos, em 2005, na Universidade de Coimbra, bem como nos anos seguintes, as 2as Jornadas de Segurança aos Incêndios Urbanos em 2011 e as 3as Jornadas de Segurança aos Incêndios Urbanos em 2013, também na Universidade de Coimbra. As edições seguintes aconteceram em diferentes locais: as 4as Jornadas de Segurança aos Incêndios Urbanos em 2014, no Instituto Politécnico de Bragança; as 5as Jornadas de Segurança aos Incêndios Urbanos em 2016, no Laboratório Nacional de Engenharia Civil em Lisboa; as 6as Jornadas de Segurança aos Incêndios Urbanos e 1as Jornadas de Proteção Civil em 2018, na Universidade de Coimbra; e as 7as Jornadas de Segurança aos Incêndios Urbanos e 2as Jornadas de Proteção Civil, em 2021, no Instituto Politécnico de Castelo Branco. As 8JORNINC apresentam grande importância num contexto atual de vários e graves incêndios urbanos, florestais e de interface em Portugal. A pertinência do tema da segurança na prevenção e no combate a incêndios, quer pelas consequências emergentes deste tipo de acidentes, quer pela necessidade de redução das ocorrências, do número de vítimas mortais, feridos, prejuízos materiais, patrimoniais, ambientais e sociais, leva a que as Jornadas se destinem a um leque alargado de profissionais e público em geral. As 3JORPROCIV têm como objetivo promover conhecimentos nas áreas da prevenção civil, de riscos e planos de emergência. Pretendem assim, contribuir para a atualização dos conhecimentos técnicos e científicos da segurança e proteção civil, no âmbito do planeamento e prevenção perante cenários de crise e emergência. As Jornadas de Proteção Civil permitem partilhar um leque de conhecimentos multidisciplinares suscetíveis de impulsionar uma intervenção por parte de técnicos, especialistas e dos agentes da proteção civil. A visão interdisciplinar e integradora dos problemas e desafios que a proteção civil apresenta será refletida na prevenção e mitigação dos riscos inerentes a uma situação de acidente. Os trabalhos apresentados nesta edição, permitirão o avanço das 8JORNINC-3JORPROCIV, através da divulgação dos recentes desenvolvimentos e do conhecimento nos domínios da segurança ao incêndio e proteção civil. Por fim, a comissão organizadora das 8JORNINC-3JORPROCIV gostaria de agradecer: - o apoio dos patrocinadores e das instituições do Sistema Científico e Tecnológico; - a todos os autores que partilharam os seus excelentes trabalhos; - e aos elementos da Comissão Científica que auxiliaram no processo de revisão. Todos em conjunto, tornaram possível a realização destas Jornadas.