Effect of nylon fabric reinforcement on the mechanical performance of adhesive joints made between glass and GFRP

The use of reinforcements in adhesive joints makes the stress distribution more uniform, improving their mechanical performance and adhesion. The present paper aims to verify the effectiveness and efficiency of the insertion of nylon 6 fabric in the adhesive layer, to study their applicability and functionality in building components. The increase in stiffness achieved by applying nylon 6 fabric in the adhesive layer between glass and GFRP pultruded profiles and steel laminates applied to GFRP beams is investigated. Three different epoxy adhesives and one epoxy resin are used and compared. Three different types of tests are carried out in order to study the different properties of the reinforcement system: tensile tests on GFRP/GFRP single-lap adhesive joints, with and without nylon fabric reinforcement; tensile tests on double-lap adhesive joints between float glass and pultruded GFRP profiles reinforced with nylon fabric according to four configurations (in the middle plane of the adhesive layer, on the glass surfaces, on the GFRP surfaces, on both GFRP and glass configurations) to verify the influence of its position; three-point bending tests on long GFRP tubular profiles reinforced with steel plates and nylon fabric in different configurations, to study resistance to bending loads. The results from the experimental campaign show the effectiveness of the reinforcement system using nylon fabric 6. In general, both a reduction in ultimate strength and an increase in joint stiffness compared to unreinforced configurations are observed

Experimental investigation on timber-glass double-lap adhesive joints

Recent advances in research in the field of structural adhesives have led to the development of new hybrid multi-material structures. In this type of application, different components are combined to create high performance structural elements characterized by low weight and ease of installation. In this experimental study, a series of shear tests were conducted on double-lap adhesive joints, in which float glass was adhesively bonded with mahogany and pine adherends. In particular, the effects resulting from the use of two types of selected epoxy adhesives and different surface treatment methods for timber adherends (i.e. dipping and varnishing treatments) were analysed. This experimental campaign aims to verify the compatibility of the adhesive joint between the mentioned adherends, with particular reference to its application in the field of civil engineering. The results obtained show that the epoxy EPX1 adhesive provides the best performance in terms of stiffness and strength for the substrate combination with untreated mahogany and float glass. In fact, this configuration leads to the stiffest type of joint while achieving high load values. EPX2 adhesive achieves higher ultimate strength values in all other combinations of adhesives analysed and exhibits greater ductility. The results demonstrate an excellent compatibility between the materials considered and the effectiveness of the adhesive joint for the intended applications

Experimental investigation on timber-glass double-lap adhesive joints reinforced with nylon fabric

Adhesive technology is widely used and studied in different fields. This joining method allows to join different materials, assembling lightweight and solid structures. However, joints are usually the most vulnerable part of a structural system. A method of reinforcing adhesive joints is the insertion of elements inside the adhesive layer, to improve the mechanical performance of the joint both in terms of ultimate strength and stress distribution. In this paper, the effect of nylon fabric reinforcement inside the adhesive layer of timber-glass adhesive joints, according to different positions, is studied and discussed. Two different epoxy adhesives have been used in double-lap adhesive joints between treated and untreated timber (i.e. mahogany) and float glass adherends. Shear tests carried out on both reinforced and unreinforced joints showed a generalised increase in terms of ductility of the reinforced configuration accompanied by a decrease in ultimate strength

Preservation of Historical Stone Surfaces by TiO2 Nanocoatings

We proposed the application of titanium dioxide (TiO2) for the preservation of historical (architectural, monumental, archaeological) stone surfaces. Solar light can activate the photocatalytic effect of TiO2 nanoparticles: heterogeneous photocatalysis is the key factor for the development of self-cleaning, depolluting and biocidal treatments able to photochemically degrade external damaging materials and prolong the durability of treated substrates, maintaining their original aspect and limiting ordinary cleaning activities. In this study, TiO2 nanoparticles dispersed in an aqueous colloidal suspension were applied directly on travertine, a light-colored limestone, by spray-coating in order to obtain a nanometric film on stone samples. To assess the feasibility of use of TiO2, we studied the characteristics of the nanocoating-stone system by monitoring the microscopic features of the coatings, the aesthetical changes induced to coated surfaces and the self-cleaning efficiency. We also monitored the self-cleaning ability over time during an accelerated ageing process to evaluate the durability of TiO2-based treatments. We confirmed both compatibility and effectiveness of TiO2 coating in the short term, anyway its efficiency decreased after artificial ageing. Further studies are necessary to better evaluate and eventually improve the stability of self-cleaning efficiency over prolonged time for outdoor stone surfaces