Surface structure laminated

One of the most often used production procedures for fabricating a high-performance structural laminate is the Autoclave/Vacuum Degassing (AC/VD) laminating process. In this process, individual prepreg plies are laid up in a prescribed orientation to form a laminate. The laminate is laid against a smooth tool surface and covered with successive layers of glass bleeder fabric, Mylar or Teflon sheets, and finally a vacuum... 

In order to establish control values for the adhesives formulated using tannins, the initial work was done with phenol-resorcinol-formaldehyde (PRF) or resorcinol-formaldehyde (RF) resins on both surfaces, but modified for the honeymoon principle. The PRF resin chosen for this work was Borden s resin LT-75 with Borden s hardener FM-260. The RF resin used for a comparison was Chembond s RF-900. These resins have been used for wood gluing in the United States for more than two decades, especially for the manufacture of structural laminated timbers. 

Emoto, K. Nagasaki, Y. Kataoka, K. A coreshell structured hydrogel thin layer on surfaces by lamination of a poly(ethylene glycol)-b-(D,L-lactic acid) micelle and polyallylamine. Langmuir 2000, 16, 5738-5742. 

As the trapped solution becomes more dilute, it increases in volume and creates a hydraulic pressure within the laminate. This process can take many years, and in well manufactured structures it may never result in visible damage. But the internal pressure built up in the laminate may eventually manifest itself as blisters on the surface of the structure, usually echoing delaminations between the gelcoat and the structural laminate. This problem is of especial concern to the yachting fraternity, which has a signiflcant remedial treatment industry. Repairs can be expensive and unless the root cause is eliminated, remedial work will not completely solve the problem. 

To maintain the resin content gradient through the laminate thickness and to avoid unwanted resin flow between the layers, the corrosion barrier is allowed to gel before the structural laminate is applied. After the gelling of the corrosion barrier another CSM is applied before either filament winding commences or WR is applied. The resin in the corrosion barrier is allowed to gel but not to cure completely. If it is completely cured it will be difficult to obtain good adhesion between the two layers and grinding of the outer surface of the corrosion barrier will be required prior to commencing the buildup of the structural layer. 

Composites, as distinct from metals, are heat insulators. This means that if the vessel has no outer wall insulation, then despite the inner surface of the composite laminate being at a higher temperature than the resin HDT, the full thickness of the structural wall is often at a substantially lower temperature. When analysing the structural integrity of a vessel, it is the temperature that the structural laminate is likely to experience which is most important. 

The attenuated reflectance technique presents an excellent example of how radiation at sample surface can enhance signal-to-noise ratio. Details of general optics and reflectance techniques can be found in the classic text (10). This technique is used extensively to determine differences between the structure of polymers in surface and bulk phases. Commercial accessories make these spectroscopic experiments easy to perform, although quantitative analysis of the data remains difficult. Examples of ATR applications include chemical composition analysis of polymers, surface orientation resulting from various processing methods, and chemical or thermal degradation of polymers. For samples such as powders or poorly defined surfaces, the diffuse reflectance technique can be used (11). In addition, the photoacoustic technique has been used to probe surface structure and multilayer structure commonly found in polymer laminates (17). In all these cases, optical effects can complicate analysis of infrared spectra. Nevertheless, these data have proven very useful in analytical applications. 

Prerequisite for the successful use of these technologies is the selection of a suitable surface treatment process. Here, in addition to the specifications (e.g., mold steel, surface structure, used molding compound, and geometry), the adverse effects of the individual laminates are considered as well. 

Pure UP or VE resins exhibit notably better resistance than corresponding glass fiber reinforced composites. This fact has led to the introduction of resinous surface coatings for all glass fiber-reinforced molded parts under medial loads - so-called gel coats. With the intensive utilization of UP and VE resins in corrosive environments, the composition of the protective coating as a chemical protective layer for the structure laminate is described in DIN 18820 [8] part 3. 

The topcoat needs to completely encapsulate the CFRP system with no fiber strands exposed and needs to be applied within the manufacturer-specified application time window to ensure appropriate adhesion to the reinforcing fabric and to prevent amine blush. If conditions prevent the application of the topcoat within the manufacturer s specified application window, a solvent wipe, as recommended by the manufacturer, is to be apphed to the surface of the structural laminate to remove all amine blush. Localized and small blisters are to be removed and sanded, and the topcoat material reapplied as per the manufacturer s recommendations. The topcoat is to be inspected periodically and maintained as specified by the manufacturer to ensure its effectiveness. 

A laminate is a bonded stack of laminae with various orientations of principal material directions in the laminae as in Figure 1-9. Note that the fiber orientation of the layers in Figure 1-9 is not symmetric about the middle surface of the laminate. The layers of a laminate are usually bonded together by the same matrix material that is used in the individual laminae. That is, some of the matrix material in a lamina coats the surfaces of a lamina and is used to bond the lamina to its adjacent laminae without the addition of more matrix material. Laminates can be composed of plates of different materials or, in the present context, layers of fiber-reinforced laminae. A laminated circular cylindrical shell can be constructed by winding resin-coated fibers on a removable core structure called a mandrel first with one orientation to the shell axis, then another, and so on until the desired thickness is achieved. 

Developments in glued laminated structures and panel products such as plywood and chipboard raises the question of the durability of adhesives as well as wood. Urea-formaldehyde adhesives are most commonly used for indoor components. For exterior use, resorcinol adhesives are used for assembly work, whilst phenolic, tannin and melamine/urea adhesives are used for manufactured wood products. Urea and casein adhesives can give good outdoor service if protected with well-maintained surface finishes. Assembly failures of adhesives caused by exudates from some timber species can be avoided by freshly sanding the surfaces before glue application. 

A surface is that part of an object which is in direct contact with its environment and hence, is most affected by it. The surface properties of solid organic polymers have a strong impact on many, if not most, of their apphcations. The properties and structure of these surfaces are, therefore, of utmost importance. The chemical stmcture and thermodynamic state of polymer surfaces are important factors that determine many of their practical characteristics. Examples of properties affected by polymer surface stmcture include adhesion, wettability, friction, coatability, permeability, dyeabil-ity, gloss, corrosion, surface electrostatic charging, cellular recognition, and biocompatibility. Interfacial characteristics of polymer systems control the domain size and the stability of polymer-polymer dispersions, adhesive strength of laminates and composites, cohesive strength of polymer blends, mechanical properties of adhesive joints, etc. 

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