138 documents found, page 1 of 14
Low velocity impact study of vacuum bag infused bouligand inspired composites
Amorim, Luís Manuel Machado; Santos, Ana Raquel Ribeiro; Nunes, J. P.; Viana, J. C.This work proposes three Bouligand-inspired layups to enhance low velocity impact (LVI) damage resistance and tolerance of convectional aircraft composite laminates. Two Bouligand-like (HL and HL_S) and one hybrid design layup, merging conventional and Bouligand architecture (HYB), were produced by vacuum bag infusion. Their performance under LVI, at 13.5, 25 and40 (J), and compression after impact (CAI) tests ...
A novel strategical approach to mitigate low velocity impact damage in composit...
Amorim, Luís Manuel Machado; Santos, Ana Raquel Ribeiro; Nunes, J. P.; Dias, Gustavo R.; Viana, J. C.This paper describes a new interleaving methodology to improve composite laminates' low velocity impact (LVI) damage resistance. The approach relies on analyzing interlaminar stress in a conventional aircraft laminate to determine the appropriate interleaving strategy. A model was built to identify the larges interlaminar stress, and two interleaving strategies were defined, normal and shear stress. Four thin i...
Multilayer composites for application in bulletproof vests
Malheiro, Maurício José Aires; Nunes, J. P.The quest for lighter and more flexible body armour solutions demands for the development of new materials or the application of existing materials not traditionally used in this field. An example is Shear Thickening Fluids (STFs), which have been the subject of research for the past two decades, but despite the results obtained so far, considering the potential adoption of STF for ballistic strength enhancemen...
New embeddable layer concept for real-time monitoring on composite materials
Correia, J.; Rocha, Helena Cristina Lopes; Alves, R.; Nunes, J. P.; Viana, J. C.Nowadays, the broad application of composite materials in high profile engineering structures demands the use of real-time monitoring methods to ensure they are behaving in accordance with their mechanical design and in order to avoid any eventual unpredictable failure [1]. The current work presents new layer concepts to be embedded within composite laminate structures with the purpose of monitoring them in rea...
Processing and structural health monitoring of a composite overwrapped pressure...
Rocha, Helena Cristina Lopes; Antunes, Paulo; Lafont, Ugo; Nunes, J. P.A process and Structural Health Monitoring system was implemented on a Composite Overwrapped Pressure Vessel (COPV) for hydrogen storage at 350 bar to be used in a fuel-cell system of an Unmanned Aerial Vehicle. This work reports the embedment strategy of optical fibre Bragg grating (FBG) sensors to monitor the full life cycle of the vessel, consisting of an aluminium liner and a wound carbon fibre reinforced p...
Process and structural health monitoring of a composite overwrapped pressure ve...
Rocha, Helena Cristina Lopes; Antunes, P.; Lafont, U.; Nunes, J. P.Replacements for fossil fuels in the transportation industry are being explored, to restrain global warming. Hydrogen-powered fuel cell systems, with Composite Overwrapped Pressure Vessels (COPVs) for hydrogen storage, are regarded as a viable alternative energy solution. COPVs, which consist of a fibre reinforced polymer composite overwrap wound around a liner, are the most weight efficient pressure vessel sol...
New operational load monitoring approach using digital image correlation and im...
Mucha, W.; Kokot, G.; Viana, J. C.; Nunes, J. P.The following paper presents a novel approach that can be applied to Operational Load Monitoring and Structural Health Monitoring processes. The approach is based on artificial intelligence (AI) and digital image correlation (DIC) techniques. DIC is an optical method that allows measuring full-field structural displacements and strains. In the presented approach only a relatively small fragment of the material'...
Carbon nanotubes based multi-directional strain sensor
Santos, Ana Raquel Ribeiro; Amorim, L.; Nunes, J. P.; Silva, A. F.; Viana, J. C.In this work a new carbon nanotubes (CNT) based multi-directional strain sensor capable of quantifying and indicate strain direction is foreseen. This work investigates the electromechanical behavior of an aligned CNT sensing patch strained at 45◦ in order to validate its multi-directional sensing capability. Vertically aligned CNT forests are produced by chemical vapor deposition (CVD) and then mechanically kn...
Smart operational load monitoring using decision trees and artificial neural ne...
Mucha, W.; Viana, J. C.; Nunes, J. P.Operational Load Monitoring is an industrial process that allows to predict the remaining in-service life of a mechanical structure under variable loads. Data from sensors embedded or mounted on the structure is acquired and allows to estimate the number and amplitude of load cycles that the structure has withstood so far in its working environment. This process is especially important in the aerospace industry...
FBG sensors for process and structural health monitoring of a small type III co...
Rocha, Helena Cristina Lopes; Antunes, Paulo; Lafonte, Ugo; Nunes, J. P.In this work, fibre Bragg grating (FBG) sensors were embedded in a 1-litre type III composite overwrapped pressure vessel (COPV) for an unmanned aerial vehicle (UAV), during its manufacturing for process and structural health monitoring (SHM). A single optical fibre having eight FBG sensors was fixed around an aluminium liner to form a grid network. The carbon fibre/epoxy composite layers were wound on top of i...