A request of material change when performing repairs on composite parts of SAABs JAS 39 Gripen has lead to the initiation of this project. The aim is to create a quicker and more robust repair method. The requested method of repair is to use a direct-cured repair patch made of CFRP fabric instead of CFRP tape and to mount the patch with a scarf joint, see Figure 1.1. The fabric patch should then provide a robust quasi-isotropic repair, where the operator not is dependent of complete design data such as ply-directions etc. Today tape repairs are made on tape laminate and fabric repairs made on fabric laminate. The new method is to repair tape laminate with a fabric patch. This project will evaluate the possibility of implementing this method. The work started with a literature study to find out how repairs in composite parts of the airframe are being performed today. SAABs in-house analytical tools were then used to try to predict the results and examine some of the details in the questions at issue. Finite element models were then constructed to simulate a previous physical test program conducted to validate a repair method using a step joint and a direct-cured repair patch. If the FE models could show similar results as the physical tests the results from the FE models then can be assumed to be credible. The results of this project indicate that the change from fabric to tape in the repair patch can be done without disturbing the load path of a quasi isotropic composite laminate. Fabric repairs in orthotropic composite plates results in a knock-down of about 40%. The use of a scarf joint instead of a step joint should also work well as the repair patches show similar strains in the centre of the patches. The difference between step joint and scarf joint is the strain near the edge of the patch. It increases with scarf joint and it may lead to an earlier fibre failure in the repair patch. Results from the analysis of the bonded joint indicate that a scarf joint yields in a lower and more evenly distributed shear stress than the step joint. This indicates that the bonded joint in the step joint will reach failure earlier then the scarf joint.

Microplasmas são plasmas gerados em espaços com dimensões reduzidas, tipicamente, de dezenas a centenas de micrômetros. Apresentam como principal vantagem a possibilidade de se obter plasmas frios com densidades elevadas com baixo consumo de energia em pressões maiores do que em reatores convencionais, reduzindo sensivelmente o custo do equipamento. Um gerador de microplasma inédito foi desenvolvido neste trabalho, utilizando a tecnologia LTCC. O dispositivo é constituído por dois eletrodos paralelos de prata-paládio perfurados por centenas de microfuros, formando microcanais. O microplasma é gerado na região entre os eletrodos e é conduzido para fora do gerador através dos microcanais, constituindo um plasma remoto que pode interagir com a superfície de um material a ser processado. Os microfuros formam a estrutura de um microcatodo oco. Na fabricação, as camadas de cerâmica verde foram usinadas com uma máquina de CNC e os eletrodos foram obtidos por serigrafia. O método de pós-sinterização utilizando a cerâmica de transferência mostrou ser bastante reprodutível e produziu eletrodos totalmente planos, sem arqueamento. O gerador de microplasma foi instalado dentro de um reator RIE convencional e o microplasma foi gerado em DC e RF. A caracterização dos microplasmas de Ar, O2, N2 e He foi realizada por meio de curvas VxI, sonda dupla de Langmuir e espectroscopia de emissão óptica. Para descargas DC, em condições de baixa vazão de gás e elevada pressão, as curvas VxI mostraram três modos de descarga: catodo oco, normal e anormal. O efeito catodo oco foi evidenciado também pelos espectros de emissão óptica que mostraram raias na faixa de 300 a 450 nm, que indicam a presença de elétrons de alta energia. Essas raias foram mais fortemente evidenciadas em descargas RF. Temperaturas de elétrons elevadas, na faixa de 10 a 30 eV, foram obtidas através de medidas com a sonda dupla de Langmuir, nas condições em que o efeito catodo oco foi observado. A aplicabilidade do gerador de microplasma foi testada com foco no tratamento de superfície de polietileno e os resultados mostraram alta capacidade de redução do ângulo de contato e aumento da molhabilidade superficial, demonstrando, conseqüentemente, substancial modificação da energia de superfície do material, através desse processo a microplasma. / Microplasmas are plasmas generated in spaces with reduced dimensions, typically ranging from tens to hundreds of microns. The major advantage of a microplasma generator is the possibility of glow discharge generation with high plasma density and low power consumption at pressures higher than usually observed in conventional plasma reactors, reducing considerably the equipment cost. A novel structure of microplasma generator was developed in this work, using the LTCC technology. The device is composed of two silver-palladium parallel electrodes perforated by hundreds of microholes, constituting microchannels. The microplasma itself is formed between the electrodes and the plasma species are carried through the microchannels to reach the processing chamber, where they can interact with the samples to be treated. The presence of microholes can promote microhollow cathode effect. In the fabrication process, green tapes were micromachined by using a CNC and the electrodes were obtained by screen printing. The post-fire method using transfer tapes has demonstrated to be very reproducible and produced very flat electrodes. The microplasma generator was mounted into a conventional homemade reactive ion etching (RIE) reactor and driven by DC and RF power supply. Characterization of Ar, O2, N2 and He microplasmas was performed by means of VxI characteristics, double Langmuir probe and optical emission spectroscopy. For DC discharges, the VxI characteristics revealed three distinct regions: microhollow cathode mode, normal glow and abnormal glow, for low gas flow rate and high pressure conditions. The microhollow cathode effect was evidenced by optical emission that presented lines in wavelengths between 300 and 450 nm, indicating the presence of high energy electrons. These emission lines have shown to be more intense in RF discharges. Double Langmuir probe diagnostic showed high electron temperatures ranging from 10 and 30 eV, under the microhollow cathode effect conditions. The microplasma generator applicability was tested focusing on the surface treatment of polyethylene film. The results showed high efficiency of this process in reducing water contact angle and thus substantially increasing the polyethylene wettability, thus demonstrating effective modification of surface energy of the material. One can conclude that among other potential applications for material processing, the microplasma generator has already shown to be a reliable tool to modify the surface energy of materials.

Objectives: To compare postoperative urinary retention and pain control when bupivacaine versus saline for hydrodissection is used while placing tension-free vaginal tape midurethral slings. Methods: A prospective, randomized, double-blind trial was performed after institutional review board approval. Sixty women were randomized to receive bupivacaine or saline for hydrodissection. Subjects and research team were blinded to subject assignments. Group characteristics were compared using the Student t test, the χ2 test, and the Mann-Whitney U test. Proportions of subjects with a successful postoperative voiding trial along with measurements of postoperative pain and analgesic use were compared using similar appropriate tests. The study was powered to detect differences in voiding trial success from an estimated 58% to greater than 90% with P < 0.05 and 0.8 power using 25 subjects per group. Results: Thirty patients were allocated to each group. One subject in the saline-only group was excluded. Group characteristics were not different. After surgery, pain medication use (20/30 vs 25/29 for bupivacaine vs saline only; P = 0.08), pain scores (36 ± 22 vs 31 ± 24; P = 0.49), and successful voiding trials did not differ (14/30 vs 19/29; P = 0.14), whereas postvoid residuals did differ (225 ± 180 mL vs 140 ± 147 mL; P = 0.043). Conclusions: Bupivacaine was not seen to improve immediate postoperative pain after placement of a tension-free vaginal tape. It did not increase the risk of failing a postoperative voiding trial. Without an obvious benefit, the use of an additional medicine is not supported. We suggest saline alone be used for hydrodissection.