Evaluation of delamination damages on composite plates using techniques of image processing and analysis and a backpropagation artificial neural network

Nowadays, drilling of carbon/epoxy laminates is extremely frequent in manufacturing and assembling processes and is normally carried through using standard drills, like twist or Brad drills. However, it is always necessary to have in mind the need to adapt properly the drilling operations and/or the drilling tools used as the risk of delamination occurrence in the laminates involved, or other kind of damages, is very high. Moreover, delamination can be critical because the mechanical properties of the produced parts can be severely affected. Thus, the production of higher quality holes, with damage minimization, is a key challenge to everyone related with composites industry to develop adequate methodologies to delamination characterization and assessment. In this paper, the delamination caused on laminates by drilling machining operations is analytically evaluated by processing and analyzing enhanced conventional radiography images of the laminates involved. In resume, in order to evaluate the delamination damage in laminates plates caused by drilling operations, the radiography images acquired are processed using a computational methodology that uses techniques of image processing and analysis and a backpropagation artificial neural network. Experimental results show that the proposed methodology can be successfully used to measure and characterize the delaminated area. Hence, using our methodology, the damage evaluation on laminates can become more accurate, efficient and simple

Effect of plug-filling, Testing velocity and temperature on the tensile strength of strap repairs on aluminium structures

In this work, an experimental study was performed on the influence of plug-filling, loading rate and temperature on the tensile strength of single-strap (SS) and double-strap (DS) repairs on aluminium structures. Whilst the main purpose of this work was to evaluate the feasibility of plug-filling for the strength improvement of these repairs, a parallel study was carried out to assess the sensitivity of the adhesive to external features that can affect the repairs performance, such as the rate of loading and environmental temperature. The experimental programme included repairs with different values of overlap length (L O = 10, 20 and 30 mm), and with and without plug-filling, whose results were interpreted in light of experimental evidence of the fracture modes and typical stress distributions for bonded repairs. The influence of the testing speed on the repairs strength was also addressed (considering 0.5, 5 and 25 mm/min). Accounting for the temperature effects, tests were carried out at room temperature (≈23°C), 50 and 80°C. This permitted a comparative evaluation of the adhesive tested below and above the glass transition temperature (T g), established by the manufacturer as 67°C. The combined influence of these two parameters on the repairs strength was also analysed. According to the results obtained from this work, design guidelines for repairing aluminium structures wer

Avaliação de ferramentas na furação de laminados compósitos

Drilling of polymeric matrix composite structuresThe development of cutting tools becomes a challenge to the industry of composite materials to obtain high quality holes, minimizing damage. This work aims to examine the influence of various parameters such as feed rate and tool geometry on thrust forces developed during drilling operations and on the extent of damage. In this work, a comparative study of tool geometry with the aim of reducing the associated damage during drilling process is presented. In the end a good combination of tool geometry and drilling parameters based on experimental work will be presented.O desenvolvimento de ferramentas de corte torna-se um desafio à indústria de materiais compósitos, na obtenção de furos de elevada qualidade, minimizando o dano. Este trabalho visa analisar a influência de vários parâmetros, tais como o avanço e a geometria de ferramenta, nas forças desenvolvidas durante a furação e na extensão do dano. Neste artigo é apresentado um estudo comparativo de geometrias de broca com o objectivo de reduzir o dano associado à furação, que permitirá determinar qual a melhor selecção de parâmetros de furação, atendendo às diferentes geometrias de ferramenta

Drilling of carbon fibre reinforced laminates : a study

The distinguishing characteristics of carbon fibre reinforced laminates, like low weight, high strength or stiffness, had resulted in an increase of their use during the last decades. Although parts are normally produced to near-net shape, machining operations like drilling are still needed. In result of composites non-homogeneity, this operation can lead to delamination, considered the most serious kind of damage as it can reduce the load carrying capacity of the joint. 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 adequate drill geometry can reduce thrust forces, thus delamination damage

Damage Assessment in Composite Laminates - A Fractal Approach

This work focuses on the assessment of the damaged area originated by drilling of composite laminates. A batch of carbon/epoxy plates was cut into test coupons and drilled under different conditions regarding feed rate and spindle speed. The use of enhanced radiography allowed the determination and assessment of the damaged area. Besides the damage assessment, other mathematical functions were used, like fractals, to characterize the damaged area. Finally the plates were mechanically tested for correlation of results

Modelação por elementos finitos do processo de furação em laminados de carbono/epóxido

Neste trabalho apresentam-se os resultados obtidos em simulações numéricas dafuração de laminados de carbono/epóxido usando elementos sólidos tridimensionais dosoftware ABAQUS® Explicit. O início e propagação do dano são simulados recorrendo ainstruções específicas do programa, bem como a remoção dos elementos ao longo doprocesso. Os resultados obtidos numericamente são comparados com resultadosexperimentais obtidos previamente pelos autores. Verifica-se uma boa concordância entre osresultados numéricos e os experimentais, confirmando a validade do modelo proposto

LeishVet update and recommendations on feline leishmaniosis

Limited data is available on feline leishmaniosis (FeL) caused by Leishmania infantum worldwide. The LeishVet group presents in this report a review of the current knowledge on FeL, the epidemiological role of the cat in L. infantum infection, clinical manifestations, and recommendations on diagnosis, treatment and monitoring, prognosis and prevention of infection, in order to standardize the management of this disease in cats. The consensus of opinions and recommendations was formulated by combining a comprehensive review of evidence-based studies and case reports, clinical experience and critical consensus discussions. While subclinical feline infections are common in areas endemic for canine leishmaniosis, clinical illness due to L. infantum in cats is rare. The prevalence rates of feline infection with L. infantum in serological or molecular-based surveys range from 0 % to more than 60 %. Cats are able to infect sand flies and, therefore, they may act as a secondary reservoir, with dogs being the primary natural reservoir. The most common clinical signs and clinicopathological abnormalities compatible with FeL include lymph node enlargement and skin lesions such as ulcerative, exfoliative, crusting or nodular dermatitis (mainly on the head or distal limbs), ocular lesions (mainly uveitis), feline chronic gingivostomatitis syndrome, mucocutaneous ulcerative or nodular lesions, hypergammaglobulinaemia and mild normocytic normochromic anaemia. Clinical illness is frequently associated with impaired immunocompetence, as in case of retroviral coinfections or immunosuppressive therapy. Diagnosis is based on serology, polymerase chain reaction (PCR), cytology, histology, immunohistochemistry (IHC) or culture. If serological testing is negative or low positive in a cat with clinical signs compatible with FeL, the diagnosis of leishmaniosis should not be excluded and additional diagnostic methods (cytology, histology with IHC, PCR, culture) should be employed. The most common treatment used is allopurinol. Meglumine antimoniate has been administered in very few reported cases. Both drugs are administered alone and most cats recover clinically after therapy. Follow-up of treated cats with routine laboratory tests, serology and PCR is essential for prevention of clinical relapses. Specific preventative measures for this infection in cats are currently not available

Drilling of fibre reinforced plastic laminates

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 delamination extent after drilling. A bearing test is performed to evaluate tool influence on the load carrying capacity of the plate. Results consider the influence of drill geometry on delamination. A correlation linking plate damage to bearing test results is presented