Thermoset fiber reinforced composites, widely used in current structural applications, have complex repair procedures and generates significant amounts of scrap due to its recycling difficulties, which does not comply with the most recent environmental restrictions. These disadvantages may be overcome by using a thermoplastic matrix phase, which is very suitable to be joined and repaired by local melting, making the composite material fully recyclable. This work presents a literature review on the joining methods applicable to thermoplastic based composites and their potential applications to be used as repair procedures in structural elements. The effectiveness of selected adhesive and fusion bonding techniques for several thermoplastic composite systems is evaluated by a comparative study based on the joints’ strength and toughness results available in the literature. This work focuses on the three most promising fusion bonding techniques: Resistance welding, induction welding, and ultrasonic welding. The advantages and drawbacks for each one of these processes are discussed, as well as their suitability for several specific structural applications. In addition, several discordant aspects for each welding technique are identified and the corresponding recommendations are discussed. A compilation of analytical models for the mechanisms of heat generation and transient heat transfer modelling is also presented for each fusion bonding process in order to promote their application in numerical modelling.

No abstract

No abstract

No abstract

No abstract

Introduction All-ceramic restorations currently dominate the market of indirect restorative materials due to their biocompatibility, longevity and superior aesthetics [ 1 ]. Silica-based ceramics, such as leucite, carry the advantage of being receptive to surface treatments, making them bondable to tooth substrates [ 2 ]. However, a standardised application protocol regarding silane coupling agents is lacking. Such step is critical to ensure durability of the restoration placed in situ . Post-etch cleaning and silane application have been proven to increase bond strength, however, this step varies for each material [ 3 ]. The aim of this research was to assess the influence of different types of silane coupling agents and respective application times on the bond strength of the ceramic-resin interface. Materials and methods Ten leucite reinforced glass ceramic blocks (IPS Empress CAD LT BL4/C 14) were divided into equal halves. Of the samples obtained, 6 were randomly divided into three groups according to the silane used: G1 BIS-Silane (Bisco, Schaumburg, IL, USA); G2 ESPE Sil Silane Coupling Agent (3 M ESPE AG, Seefeld, Germany); G3 Monobond Plus (Ivoclar-Vivadent, Schaan, Liechtenstein). Each was then divided into two subgroups, according to the surface conditioning time: T1 (1 min.) or T2 (5 min.). Each block was acid etched (HF 9.5% − 1 min), post-etching cleaned (OPA 37.5% − 1 min; ultrasonication − 2 min.) and silanized. Heat treatment was carried out at 100 °C (1 min.). Then a thin layer of Optibond FL (Kerr) adhesive was applied and each block was adhered to pre-heated resin at 55 °C. The samples were light cured for 40 s on each side (1200 mW/cm 2 ). Samples were sectioned into microspecimens (1 ± 0.2 mm 2 ) that were subjected to aging (10,000 thermocycles − 5 and 55 °C). The microspecimens were tested in tension at a crosshead speed of 0.5 mm/min, until they debonded. Data analysis was carried out by a two-way ANOVA, at a significance level of 5%. Results The group featuring BIS-Silane with longer application time (G1T2) presented a mean µTBS value (32.4 ± 19.6 MPa) significantly higher to all other groups ( p < .001). Monobond Plus registered the lowest mean µTBS value (G3T1 − 18.5 ± 7.3 MPa) and (G3T2 − 17.3 ± 5.8 MPa). The type of silane coupling agent has shown to have a significant influence on the microtensile bond strength ( p = .001; η 2 =0.16). Discussion and conclusions Some authors have previously suggested that silanization could benefit from longer application times, but seldom re...

ResumoA avaliação das propriedades reológicas de suspensões é uma parte importante no desenvolvimento de massas cerâmicas. Em processamento via úmida, o fator reológico pode ser limitante ao emprego tanto de determinada matéria-prima quanto do agente defloculante. Nesse sentido, a abordagem integrada da formulação de massas cerâmicas triaxiais juntamente com o auxílio do delineamento de misturas visa a diminuição do número de experimentos necessários para determinação de propriedades ótimas do sistema em estudo, sejam essas propriedades físicas ou reológicas. O presente trabalho tem como objetivo estudar a defloculação de massas cerâmicas triaxiais (argila/feldspato/quartzo) obtidas a partir do delineamento de misturas, através da obtenção de um modelo matemático que represente a concentração ideal de defloculante apresentada por cada composição cerâmica do diagrama triaxial. Para tanto, foram preparadas suspensões aquosas (55% de sólidos), utilizando silicato de sódio anidro (razão molar SiO 2 : Na 2 O igual a 1.3) como agente defloculante. Curvas de defloculação foram obtidas com o objetivo de determinar a concentração ideal de defloculante. Os resultados mostraram que o aumento na fração argilosa das composições estudadas conduziu a um aumento no consumo de defloculante. Palavras-chave: processamento cerâmico, silicato de sódio e delineamento de misturas. Abstract The evaluation of the rheological properties of suspensions is an important step in the ceramic slurries development. Mainly in wet processing, the rheological factor can be a limitation to the employment of determined raw material as well as the deflocculant agent. In this sense, the integrated approach of triaxial ceramics formulation and the mixture design come as an important aid to decrease the number of experiments necessary to determine the optimum properties of a system, which can be physical or rheological properties. The present work is directed towards to study the deflocculation of triaxial ceramic slurries (clay/feldspar/ quartz) obtained from the mixture design, through the determination of a mathematical model that represents the ideal deflocculant

An optimum amount of deflocculant was determined for three-component suspensions, based on a mixture design approach. Three raw materials were used, characterized as clay, feldspar and quartz. Ten compositions were prepared using the mixture design approach. Deflocculation curves were measured for suspensions with 40 wt.% of solids, adding sodium silicate as dispersant. The optimum deflocculant amount (ODA) was determined for each suspension, corresponding to the lowest value of apparent viscosity considering two nearest experimental points. It was observed that ODA increases linearly with the increase of the clay fraction in the mixture. A response surface and polynomial regression could be used to identify the composition range that satisfies usual conditions in wet ceramics processing.