Composites joining/welding

A selection of these techniques is also applicable to polymer composites (see Fibre composites - joining). However, since composites gain their superior properties from the reinforcement, the weld is inevitably the weak point in the system as the fibre will be discontinuous across the joint interface. All the welding processes are governed by the parameters time, temperature and pressure. In order to achieve high-quality welds, careful optimization of the welding parameters is required for each application. 

Plastics and Composites Joining Laboratory, Welding Engineering Program, Department of Materials Science and Engineering, Ohio State University, Columbus, OH, United States... 

Abbass Mokhtarzadeh and Avraham Benatar Plastics and Composites Joining Laboratory Department of Industrial, Welding and Systems Engineering The Ohio State University Columbus, Ohio 43221... 

Transition joints are used to join dissimilar metals where flanged, screwed, or threaded connections are not practical. They are used when fusion welding of two dissimilar metals forms interfaces that are deficient in mechanical strength and the ability to keep the system leak-tight. Transition joints consist of a bimetallic composite, a stainless steel, and a particular kind of aluminum bonded together by some proprietary process. Some of the types in use throughout the cryogenic industry are friction- or inertia-welded bond, roll-bonded joint, explosion-bonded joint, and braze-bonded joint. 

Lee and coworkers (Ref 49) have reported on a study of FSW on pure titanium. Although no details were given on the composition of material, it was similar to some type of CP titanium alloy. Plates of CP titanium, 5.6 mm (0.22 in.) in thickness, were joined by FSW using a sintered TiC tool with a water-cooling system. Welds were produced at 1100 rpm at a welding speed of 500 mm/min (20 in./min). 

The chassis structure of the hybrid low-floor COBRA tram consists of a frame and a floor module, made of welded aluminum (hollow extrusions [3]) (Fig. 32.9). The composite sandwich roof panel is glued with elastic adhesives to the aluminum roof cant rail. All heavy aggregates are positioned on top of the composite roof panel. Due to the foam core, the loads had to be introduced by additional profiles (connected to the roof cant rail) to smoothen any local peaks. The GRP sidewall panels are joined to the aluminum pillars and the major longitudinal extrusions by long running layers of the elastic adhesive Sikaflex -254 Booster. The structural analysis of this tram vehicle proved the structural integrity of the new design for the load history specified. The stiffness of the structure has been sufficient to fulfill all the deformation criteria (Fig. 32.10). Based on these results, the preproduction series of the first six COBRA trams was produced and is in normal service operation an additional 68 trams will have followed by 2010. 

Efforts to join liquid chromatographs (LCs) and IMSs at ambient pressure and with full flow of conventional columns has not been developed since stable response and high-quality spectra can be obtained at flow rates up to about 2 pL/min. Mobility spectrometers with direct flux of ESI spray into the drift tube become inoperable with liquid flows larger than 10 pL/min or liquid compositions with 50% or more water, even with a desolvation region. An interface was described to accept full liquid flow from an LC directly into the drift tube and consisted of three stainless steel rings in a Teflon housing with a stainless steel mesh welded on the third ring. 

Because of their favourable cost-performance ratio, polyvinyl chloride (PVC) coated polyester (PET) fabric is the most common basic material used. It can be applied over the whole spectrum from small temporary to wide-span structures. With a top-coat that protects the PVC from soiling and early ageing, a life-span of up to 20-25 years can be obtained. PVC-PET composites are joined by high-frequency or hot wedge welding. With flame-retardant additives to the PVC coating, fire class B1 can be achieved. 

Modern technology involves new types of materials that cannot be joined by means of traditional mechanical methods such as welds, rivets, screws, and bolts. These materials include different types of ceramics, glass ceramics, alloys, composites, etc. 

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