Optimum adhesive thickness in structural adhesives joints using statistical techniques base on Weibull distribution

The geometrical factors defining an adhesive joint are of great importance as its design greatly conditions the performance of the bonding. One of the most relevant geometrical factors is the thickness of the adhesive as it decisively influences the mechanical properties of the bonding and has a clear economic impact on the manufacturing processes or long runs. The traditional mechanical joints (riveting, welding, etc.) are characterised by a predictable performance, and are very reliable in service conditions. Thus, structural adhesive joints will only be selected in industrial applications demanding mechanical requirements and adverse environmental conditions if the suitable reliability (the same or higher than the mechanical joints) is guaranteed. For this purpose, the objective of this paper is to analyse the influence of the adhesive thickness on the mechanical behaviour of the joint and, by means of a statistical analysis based on Weibull distribution, propose the optimum thickness for the adhesive combining the best mechanical performance and high reliability. This procedure, which is applicable without a great deal of difficulty to other joints and adhesives, provides a general use for a more reliable use of adhesive bondings and, therefore, for a better and wider use in the industrial manufacturing processes

Modelo de estimación de costes para tolerancias de diseño en la ingeniería de los procesos de producción

La disponibilidad los valores coste-tolerancia de un proceso de producción es un aspecto de interés desde el punto de vista de la Ingeniería de Proyectos en general y de la Ingeniería de Procesos de Producción en particular. Tanto en la fase de planificación de un proyecto como en las etapas de diseño de cada uno de los procesos de producción que posibilitarán su ejecución, las especificaciones del producto deben estar contenidas en un intervalo de tolerancia cuyo coste de obtención es tanto mayor cuanto menor es el margen de variación admisible. Por este motivo, el conocimiento del coste asociado a cada tolerancia es una herramienta de gran utilidad para el ingeniero de proyectos. A pesar de su interés, las curvas de coste-tolerancia se manejan con menor profusión de la que sería deseable, dada la gran interdependencia existente entre ellas y la localización espacio-temporal de los recursos a las que se asignan. El presente trabajo propone un método que permite establecer una relación coste-tolerancia a los procesos de producción de la Ingeniería de Proyectos, basada de la variabilidad derivada de los recursos de cada proceso

Multi-criteria selection of structural adhesives to bond ABS parts obtained by rapid prototyping

One of the most used methods in rapidprototyping is Fused Deposition Modeling (FDM), which provides components with a reasonable strength in plastic materials such as ABS and has a low environmental impact. However, the FDM process exhibits low levels of surface finishing, difficulty in getting complex and/or small geometries and low consistency in “slim” elements of the parts. Furthermore, “cantilever” elements need large material structures to be supported. The solution of these deficiencies requires a comprehensive review of the three-dimensional part design to enhance advantages and performances of FDM and reduce their constraints. As a key feature of this redesign a novel method of construction by assembling parts with structuraladhesive joints is proposed. These adhesive joints should be designed specifically to fit the plastic substrate and the FDM manufacturing technology. To achieve this, the most suitable structuraladhesiveselection is firstly required. Therefore, the present work analyzes five different families of adhesives (cyanoacrylate, polyurethane, epoxy, acrylic and silicone), and, by means of the application of technical multi-criteria decision analysis based on the analytic hierarchy process (AHP), to select the structuraladhesive that better conjugates mechanical benefits and adaptation to the FDM manufacturing proces

Influencia de la modificación de la estructura cristalina superficial de un aluminio en el valor de su energía superficial, al ser atacado con diferentes tratamientos mecano-químicos

En el trabajo se analizaron las modificaciones que diferentes ataques superficiales empleados para modificar la topografía superficial inducían en la estructura cristalina del sustrato y sus consecuencias en las características termodinámicas de la superficie con vistas a la adhesión. Se consideraron cuatro tipos diferentes de ataques superficiales y se analizaron los efectos que habían producido sobre la energía superficial del sustrato de aluminio. Se comprobó mediante XRD la modificación inducida por los distintos tratamientos en la estructura cristalina del aluminio utilizado como sustrato

Influencia de las características superficiales de un sustrato en la resistencia de una unión adhesiva

Uno de los objetivos que se plantean cuando se realiza una unión adhesiva es que su resistencia sea lo más elevada posible para los esfuerzos a los que va a estar solicitada. Además de las propias características del adhesivo empleado, está la resistencia que se genera en la interfase. En trabajos anteriores se ha caracterizado la topografía de la superficie del sustrato. En este trabajo se han realizado ensayos de resistencia de la unión adhesiva sometida a ensayos de tracción pura, buscando la relación con las características de las superficies tratadas con diferentes tratamientos mecánicos y químicos. Se ha comprobado que el valor de la rugosidad influye en la resistencia, pero condicionado por el tratamiento aplicado

Degradation in seawater of structural adhesives for hybrid fibre-metal laminated materials

The adhesives used for applications in marine environments are subject to particular chemical conditions, which are mainly characterised by an elevated chlorine ion content and intermittent wetting/drying cycles, among others.These conditions can limit the use of adhesives due to the degradation processes that they experience. In this work, the chemical degradation of two different polymers, polyurethane and vinylester, was studied in natural seawater under immersion for different periods of time.The diffusion coefficients and concentration profiles of water throughout the thickness of the adhesiveswere obtained.Microstructural changes in the polymer due to the action of water were observed by SEM, and the chemical degradation of the polymer was monitored with the Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The degradation of the mechanical properties of the adhesive was determined by creep tests withMixed Cantilever Beam (MCB) specimens at different temperatures. After 180 days of immersion of the specimens, it was concluded that the J-integral value (depending on the strain) implies a loss of stiffness of 51% and a decrease in the failure load of 59% for the adhesive tested

Influence of surface treatment on the surface energy of an aluminium substrate

The mechanisms by which adhesion occurs are known. In all cases, the search for an adequate surface condition is decisive in achieving a good adhesion. For this reason, the researches usually work on modifying the surface roughness or improving the thermodynamic characteristics of the surface. The objective on this work is to analyse influence of different attack types (chemical, mechanic, with laser...) which are used to improve surface finish, roughness and surface energy. We have analysed the effects that have produced in the contact angle, measuring the surface energy by the Zisman method. The results revealed that the method of attack has more influence on the value of surface energy than the values of roughness obtained, which can make rethink the type of surface treatment to improve adhesion

Analysis of E-Scooter Vibrations Risks for Riding Comfort Based on Real Measurements

Means of transport should be able to fulfil their main function safely and comfortably for travellers and drivers. The effects of vibrations on ride comfort are in the frequency range of 0.5 to 80 Hz and can be analysed using the UNE-2631 standard. This type of analysis has been conducted for several means of transport (bicycles, motorcycles, cars, trucks, etc.), but the literature on e-scooter comfort is very scarce. Existing research describes methodologies, simulation models, and a few measurements related to e-scooter comfort. This paper presents, for the first time, a comfort analysis using an Arduino-based data acquisition system at a sampling frequency of 200 Hz (higher than that in previous studies). Acceleration and speed measurements were obtained by sensorising an e-scooter with inflated wheels without any additional damping systems, which is one of the commonly used e-scooter types. In this study, the comfort for two different speeds (20 and 28 km/h), two types of pavements (pavers and asphalt), and two drivers with different weights was investigated. The results indicate the lowest comfort values for higher velocities and paver pavement. Furthermore, the comfort values were extremely low for all scenarios. In addition, the results demonstrate the necessity of using a sampling rate of at least 80 Hz for this e-scooter model

Analysis of the Behavior of Fiberglass Composite Panels in Contact with Water Subjected to Repeated Impacts

One of the most common applications of glass fiber composite materials (GFRP) is the manufacturing of the hulls of high-speed boats. During navigation, the hull of these boats is subjected to repetitive impacts against the free surface of the water (slamming effect), which can cause severe damage to the material. To better understand the behavior of the composite material under this effect, in the present work, an experimental test has been carried out to reproduce the slamming phenomenon in GFRP panels by means of a novel device that allows this cyclic impact to be obtained while the panels are always in contact with water. By means of non-destructive ultrasound inspection in immersion, it has been possible to establish the evolution of the damage according to the number of impacts received by each panel. Destructive tests in the affected zone, specifically shear tests (Iosipescu test), allow determination of the loss of mechanical properties experienced by the material after receiving a high number of impacts in the presence of water (up to 900,000 impact cycles in some panels). The behavior of the material was found to be very different in wet and dry conditions. Under dry conditions, the material loses stiffness as the damage density increases and its shear strength also decreases, as does displacement at maximum load. For wet conditions, the material shows higher displacements at maximum load, while the shear strength decreases with increasing stiffness