Mechanical properties of a reversible adhesive used to separate adhesive joints

In this work, the mechanical characterization of adhesive joints made with athermoplastic adhesive, modified and not modified, has been presentedtogether with the separation tests that are possible by the use of metalnanoparticles embedded within the adhesive. A polyolefin adhesive has beenmodified with two weight concentrations (5% and 10%) of iron oxidenanoparticles. These particles increase their temperature under electromag-netic field; in this way, they are able to melt the adhesive and, therefore,separate the adhesive joints. The mechanical properties of single lap joints(SLJs) prepared with the neat and modified adhesives have been performed byusing different overlap lengths and thicknesses. SLJs prepared with thenanomodified adhesive present higher loads compared with the neat one.Separation tests have been carried out on SLJ specimens to measure the timesneeded to disassemble the adhesive joints. Scanning electron microscopeanalysis has been carried out to study the distribution of the particles

mechanical characterization and separation tests of a thermoplastic reinforced adhesive used for automotive applications

Abstract In the last decades, the use of structural and no structural adhesive has been increasing a lot in the automotive sector due to the advantages they can offer compared to traditional fasteners. Although they present many advantages, the impossibility to dismantle easily adhesive joints in order to substitute, recycle, reuse vehicle components or avoid waste for bonding errors is a factor that can limit their use. Furthermore, in Europe, the need to separate vehicle components for reuse and recycling is constrained by two Directives, 2000/53/EC and 2000/64/EC. These Directives set the objectives of reuse and recyclability for automotive vehicles, which are 95% and 85% respectively by an average weight per vehicle. For these reasons, it is very important to find a feasible solution to these problems. A promising technology for the separation of plastic joints, bonded with thermoplastic adhesives, uses nanomodified thermoplastic adhesives that are sensitive to electromagnetic fields. In this work, the mechanical behavior of adhesive joints made with a polyolefin adhesive, used in the automotive industry for bonding plastic components, have been studied. In particular, the adhesive has been modified with three different weight concentrations (3%, 5% and 10%) of iron oxide nanoparticles in order to make it sensitive to electromagnetic fields. These nanoparticles heat when are under the effect of an electromagnetic field and consequently they can melt the thermoplastic adhesive allowing for the joint separation. The mechanical properties of the joints prepared with the pristine and nanomodified particles have been studied by means of SLJ specimen with different overlap length and thicknesses. The adhesive joints prepared with the modified adhesives present a slightly higher load and a larger ductility compared to the ones prepared with the pristine one. Furthermore, separation tests have been performed in order to assess the times to disassemble these adhesive joints. Scanning electron microscope analysis has been used to assess the dispersion of the particles

Thermoplastic Adhesive for Automotive Applications

The objective of this study is to give a general overview on the thermoplastic adhesives used in the automotive sector. Some of the main applications in which the hot-melt adhesives (HMAs) are used in automotive industries are indicated, together with the adhesive characteristics that explain the reasons for their adoption. The chemical and mechanical behavior of these adhesives and the generally used experimental characterization methods are presented and opportunely criticized. In this study, some of the main properties of thermoplastic adhesives are reviewed together with the standard tests used for their characterization. For what concerns the structural performance, single lap joint test is used to determine the shear strength of the adhesive joint. Thermogravimetric analysis and Fourier transform infrared spectroscopy are used to characterize the chemical properties of the adhesive. This study clarifies what are the potentialities of a thermoplastic adhesive in car industries compared to other adhesives

Physics based data driven method for the crashworthiness design of origami composite tubes

A novel method based on a physics informed data driven model is developed to design an origami composite crash tube. The structure consists of two axially stacked basic components, called modules. Each module presents lower and upper square sections with an octagonal section in the middle. The parameters of the octagonal cross-section and the height of each module are optimized to maximize the energy absorption of the tube when subjected to an axial impact. In contrast to standard surrogate modelling techniques, whose accuracy only depends on the amount of available data, a Physics-informed Neural Network (PINN) scheme is adopted to correlate the crushing response of the single modules to that of the whole origami tube, constraining the data driven method to physically consistent predictions. The PINN is first trained on the results obtained with an experimentally validated Finite Element model and then used to optimize the structure. Results show that the PINN can accurately predict the crushing response of the origami tube, while consistently reducing the computational effort required to explore the whole design domain. Also, the comparison with a standard Feed Forward Neural Network (FFNN) shows that the PINN scheme leads to more accurate results

Regorafenib in combination with silybin as a novel potential strategy for the treatment of metastatic colorectal cancer

Regorafenib, an oral multikinase inhibitor, has demonstrated survival benefit in metastatic colorectal cancer (mCRC) patients that have progressed after all standard therapies. However, novel strategies to improve tolerability and enhance anti-cancer efficacy are needed

Rationale and design of MILES-3 and MILES-4 studies: two randomized phase III trials comparing single-agent chemotherapy versus cisplatin-based doublets in elderly patients with advanced non-small cell lung cancer

BACKGROUND: Platinum-based chemotherapy is the cornerstone of treatment of advanced non-small-cell lung cancer (NSCLC) patients, but the efficacy of adding cisplatin to single-agent chemotherapy remains to be demonstrated in prospective phase III trials dedicated to elderly patients. Furthermore, the superiority of cisplatin/pemetrexed over cisplatin/gemcitabine in non-squamous NSCLC has not been confirmed prospectively. We present the rationale and design of two open-label, multicenter, randomized phase III trials for elderly patients with advanced NSCLC∶ Multicenter Italian Lung cancer in the Elderly Study (MILES)-3 and MILES-4. The aim is to evaluate the efficacy of adding cisplatin to single-agent chemotherapy (both trials) and the efficacy of pemetrexed versus gemcitabine in non-squamous tumors (MILES-4). PATIENTS AND METHODS: Both trials are dedicated to first-line therapy of patients older than 70 years with advanced NSCLC, ECOG performance status 0-1. In the MILES-3 trial, patients are randomized in a 1∶1 ratio to gemcitabine or cisplatin/gemcitabine. In the MILES-4 study patients with non-squamous histology are randomized, in a factorial design with 1∶1∶1∶1 ratio, to four arms: gemcitabine (A), cisplatin/gemcitabine (B), pemetrexed (C), cisplatin/pemetrexed (D). Two comparisons are planned∶ A+C vs B+D to test the role of cisplatin; A+B vs C+D to test the role of pemetrexed. Primary endpoint of both trials is overall survival. Secondary and exploratory endpoints include progression-free survival, response rate, toxicity, and quality of life. CONCLUSIONS: MILES-3 and MILES-4 results will add important evidence about the role of cisplatin-based doublets and pemetrexed in the first-line therapy of elderly patients with advanced NSCLC

Functionalization of adhesives and composite matrix by micro and nanoparticle addition

The use of nano and microfillers in research and industrial areas have been increasing in recent decades. In material industry especially, the combination of specific nano and microparticles properties has been studying since they can offer a great contribution to the resolution of tough issues. One of these issues is the possibility to disassemble components for repairing, recycling or avoiding waste when errors occur in manufacturing processes. The disassembly of mechanical component is still an open issue and there are many technical problems that are involved in this process. For example, the possibility to have a clean surface of the separated component after the disassembly or the possibility to introduce damages to other linked components. This dissertation investigates the possibility to disassemble a hot-melt adhesive, used in automotive industries to join plastic components, by embedding iron nanoparticles, Fe3O4, that are sensitive to electromagnetic induction. This peculiarity makes the modified adhesives able to melt when an electromagnetic field is oriented on it and so the joint separation is possible. The mechanical and physical properties of these nanomodified adhesives, with different particles concentrations of iron oxide, were studied and compared with the pristine adhesive. This correlation was necessary in order to assess the possibility to use these modified adhesives in the vehicle assemblies since the pristine adhesive is already used by some car manufacturers for internal and external components. Separation tests of plastic joints were evaluated and the most sensitive factors were stated and analysed. The shape of the inductor coil, the diameter of the pipe coil, the frequency of the applied magnetic field and the applied current were found to be influencing factors of the induction heating process. The possibility to use cheaper particles, iron microparticles coupled with electromagnetic induction, together with the possibility to bond composite, glass fibre-reinforced plastics (GFRP), substrates were assessed as well. Composite components have been replacing many structural and non-structural components in automotive design in order to reduce the vehicle weight. The opportunity to disassemble adhesive with graphene nanoparticles embedded in the same hot-melt adhesive and coupled with microwave was assessed as well. The heating of this particles is possible by means of the π electron mechanism In recent decades, researchers and industries have been also investigating the possibility to make a material electrically conductive. In this PhD dissertation, the possibility to make a structural epoxy resin electrically conductive have been discussed as well. In order to make the material electrically conductive, different coatings of glass spheres with conductive GnPs were tried, as well, but in these cases, the coating results was not satisfactory. For these reasons the chosen filler concentration for these tests was set at 1% (volume fraction) for the conductive filler and 30% (volume fraction) for the hollow glass spheres. These were the maximum concentration that it was possible to embed in the epoxy matrix in order to obtain an easy processability of the material. The modified epoxy resins were not conductive they showed interesting mechanical properties especially under compressive load

Experimental Study on the Effect of Bonding Area Dimensions on the Mechanical Behavior of Composite Single-Lap Joint with Epoxy and Polyurethane Adhesives

The effects of joint geometry parameters, such as adherend thickness (1.76, 3.52 mm), joint width (10, 20, 30 mm), and overlap length (10, 20 mm), on the behavior of single-lap joints (SLJs) under tensile loading are investigated in this study. Peak force, joint stiffness, shear stress, and normal stress are the investigated properties. SLJs are manufactured with carbon fiber composite adherends and two different types of adhesives, polyurethane and epoxy, which present a flexible and rigid mechanical response. The results showed that increasing all 3 geometric parameters (L, W, T) leads to a significant increase in the load capacity of polyurethane joints (on average, 88.4, 101.5, and 16.9%, respectively). For epoxy joints, these increases were 47.7, 100, and 46%, respectively. According to these results, W is the parameter with the most influence on the load capacity of the joints. However, it was observed that an increase in joint width has no significant effect on adhesive shear and a substrate’s normal stresses. Epoxy SLJs behave approximately elastically until failure, while polyurethane SLJ load-displacement curves include an initial linear elastic part followed by a more ductile behavior before the failure. Joint stiffness is affected by all the parameters for both adhesive types, except for overlap length, which led to a negligible effect on epoxy joints. Moreover, the damage surfaces for both types of joints are analyzed and the internal stresses (shear and peel) are assessed by using the analytical model of Bigwood and Crocomb