Numerical prediction of the stress state in CFRP induced by installing a blind rivet nut

The present paper offers a FE modeling strategy to predict the stress state in carbon fiber reinforced plastic (CFRP) plate material after installing a Blind Rivet Nut (BRN). In industry, a BRN is a permanent mechanical fastener used to equip plate material with a threaded part. Analogue to the installing process of the more common blind rivet, the BRN deforms plastically in such a way a counter head is formed on the underside of the plate. Simultaneously, the upper side of the deformation chamber expands in the radial direction creating an interference fit. The interference fit together with the counter head units the nut to the plate. However, the high contact forces between the BRN and the plate often cause damage in the CFRP material compromising the integrity of the joint. The latter observation implies that while setting a BRN in CFRP, the detrimental contact forces must be controlled to guarantee a qualitative joint. The necessary understanding of the stress distribution in the plate material is numerically investigated in two steps. In the first step, a computational efficient axisymmetric model is used to reveal the contract pressure between the BRN and the plate during the setting process. In the second step, the contact pressures are transferred to a 3D model of the plate. In this stage, the orthotropic properties of the composite are assigned to the plate material and an adequate failure criterion is adopted. The result is compared to a full 3D model using the Tsai – Wu failure criterion.

Conventional Selection of Mechanical Fasteners for Flat Belts

Due to the variety of materials used for flat belts of belt conveyors and the further development of material engineering in relation to these belts, the methods of their connection become an increasingly problematic issue. The belts can be connected mainly in three ways: vulcanized (weldable or heat-weldable), glued or mechanically. The latter method is one of the simplest and most universal in terms of the material variety of belts; however, there are many design variations of mechanical fasteners, and each of them has a certain advantage in a narrow group of properties, e.g., the thickness spectrum of a conveyor belt, the minimum diameter of a drive roller or the range of transferable longitudinal loads. The objective of this paper is to analyze the design solutions of commercial mechanical fasteners used mainly for flat rubber-fabric, composite or plastic belts. To fulfill this goal, a preliminary analysis of the stress distribution for an exemplary solid mechanical fastener was carried out in two cases: during ramp-up and during circulating around the roll, followed by a detailed review of commercial solutions available on the market. In addition to determining the current state of knowledge and technology and determining the state of ignorance, special algorithm and design maps have been created, thanks to which the process of selecting the right mechanical fastening will be easier. The overview includes several tables with detailed information on individual connection properties. Additionally, several design aspects were derived, within which individual mechanical connections may differ. This is to enable the generation of customized solutions in the future by proposing an appropriate mathematical model, on the basis of which it will be possible to generate optimal design properties for a given application.

Performance of Withdrawal Capacity for Mengkulang Glulam Perpendicular to the Glue Line for 14mm and 20mm Bolt Diameter

Withdrawal capacity is defined as the amount of resistance to withdrawal force in a plane normal to the surface panel. It is caused by density and internal bonding of the panel. Withdrawal capacity is one of the factors that affect the load carrying capacity of the timber connection apart from embedment strength and fastener yield moment. The European Yield Model (EYM) theory is used to predict the load capacity of the timber connection under lateral load. The sample panel is made of Glued Laminated Timber (Glulam) using Mengkulang timber species. Although Mengkulang Glulam has a good weight to strength ratio as compared to typical concrete material but it is still not widely used in Malaysia. This is mainly due to a very limited exposure on the Mengkulang Glulam usage. Withdrawal capacity is determined according to the ASTM D1761-12 using one-hole test method. Also, the ASTM D1761-12, EC5:2008 is used to determine the withdrawal capacity output. In this experiment a mechanical fastener, bolt; 14mm and 20mm were used to fix the sample panels onto the test jig. The bolt diameter influenced the withdrawal capacity. It was observed that the withdrawal capacity of 20mm bolt diameter was better than the 14mm diameter with an increment of 48.6%.

Failure Evaluation of Hybrid Joints using Taguchi Method

The structural joints for various applications like automobile, aero planes, ships etc. used mechanical fasteners or adhesives for joining purpose. The mechanical fastener increases the weight of the joints and the adhesives have a catastrophic failure nature. So to reduce the overall weight of the joint and avoid the catastrophic failure of the joint, Hybrid Joint, which is the combination of the two methods (Bolts and adhesives) is used. The Analytical Hierarchal process (AHP) is used to select the parameters that affect the performance of the joint. The selected parameters were bolt size, tightening torque, bolt hole clearance, adhesive type, adhesive thickness, overlap length and joint material and the response variables were failure load and displacement The optimum parameters were selected by using Taguchi analysis with L27 orthogonal array experimental design. The significant parameters were found to be Adhesive type, Adhesive thickness and Joint Material.

An approach of steel plate hybrid bonding technique to externally bonded fibre-reinforced polymer strengthening system

The strengthening efficiency of externally bonded fibre-reinforced polymer to concrete structure is usually limited owing to the unexpected debonding of fibre-reinforced polymer laminates. In this study, a new steel plate hybrid bonding technique was developed to supply additional anchorage for traditional externally bonded fibre-reinforced polymer strengthening system. With this approach, the fibre-reinforced polymer debonding can be effectively prevented. Moreover, the stress concentration, which probably results in a premature fracture of fibre-reinforced polymer laminates as that performed for available hybrid bonding anchorage techniques, can be eliminated by introducing a steel plate between the mechanical fasteners and fibre-reinforced polymer strips. To verify the effect of this new method, 21 carbon fibre–reinforced polymer–strengthened beams were studied on the flexural behaviours. Test results showed that, compared to available hybrid bonding anchorage techniques, steel plate hybrid bonding is more capable of making the full use of fibre-reinforced polymer laminates and further enhance the ultimate capacity and ductility of externally bonded fibre-reinforced polymer–strengthened beams. Based on the experimental results, the effect of interfacial treatment, ply of carbon fibre–reinforced polymer and mechanical fastener spacing on the failure mode and ultimate load ratio were discussed. Eventually, a simplified analytical procedure was proposed and verified to estimate the flexural resistance of steel plate hybrid bonding – fibre-reinforced polymer–strengthened beam.