Laminate Structure

Their main applications have been in heat-resistant structural laminates, electrical laminates resistant to solder baths, chemical-resistant filament-wound pipe and high-temperature adhesives. 

Classical lamination theory consists of a coiiection of mechanics-of-materials type of stress and deformation hypotheses that are described in this section. By use of this theory, we can consistentiy proceed directiy from the basic building block, the lamina, to the end result, a structural laminate. The whole process is one of finding effective and reasonably accurate simplifying assumptions that enable us to reduce our attention from a complicated three-dimensional elasticity problem to a SQlvable two-dimensinnal merbanics of deformable bodies problem. 

For thick epoxy laminates processed in the autoclave, voids once formed and stabilized can only be removed by dissolution or by resin flow. Furthermore, resin gradients are deleterious to structural laminates. These two key phenomena make an understanding of resin transport vital to the development of any processing model. 

Integrity of Glue Joint in Structural Laminated Wood Products for Exterior Use, Test for D 1101... 

D 2559 Specification for Adhesive for Structural Laminated Wood Products for Use... 

D 3024 Specification for Protein Base Adhesive for Structural Laminated Wood... 

The fabrication of composite laminates having a thermosetting resin matrix is a complex process. It involves simultaneous heal, mass, and momentum transfer along with chemical reaction in a multiphase system with time-dependent material properties and boundary conditions. Two critical problems, which arise during production of thick structural laminates, are the occurrence of severely detrimental voids and gradients in resin concentration. In order to efficiently manufacture quality parts, on-line control and process optimization are necessary, which in turn require a realistic model of the entire process. In this article we review current progress toward developing accurate void and resin flow portions of this overall process model. 

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. 

Other linear polymers suitable for high-temperature structural laminates are obtained by the reaction of bis(furfuryl) imide via Diels-Adler reactions (56,57). Stability in air up to 500 °C has been reported for these polymers. The prepolymers have pendent phenyl substituents and are soluble in organic solvents, an important processing improvement for hetero-aromatic polymers. 

Epon HPT . [Shell] Epoxy matrix resin used for advanced composites with glass, carbon, aramid or b n fibers, high-performance structural laminates and adhesives, preptegs. 

It is now possible to design materials possessing permittivities which have low variation with the frequency (e"a(w ) or high (e"ao) ) directly correlated to the intrinsic conductivity of the polymer. To obtain the best performance (large bandwidth) these materials have to be associated in multilayer structures. Moreover, the use of structural laminates allows the integration of two functions (stealth and mechanical). 

Recently Haggis [30] and later Hipchen [31] reported on methods to prepare polyisocyanurate structural laminates. Recent reviews on the subject of isocyanurate foams are worth consulting for additional references [32, 32a]. 

Fracture toughness tests for isotropic materials normally use edge-notched flexure beams and compact tension specimens. These methods are. as for the impact tests, only suitable for the injected or compression molded materials, which do not have a strongly laminated structure. Laminated composite materials have their primary failure path between the layers, and a new set of test geometries has been developed. 

ASTM D-1101, Standard Test Method for Integrity of Glue Joints in Structural Laminated Wood Products for Exterior Use. Two methods are outlined in this standard for using an autoclave vessel to expose the joint alternately to water at... 

Next to tubes and fibers, tbin ceramic sheets are also a very interesting subject for the development of thermoplastic ceramic extrusion systems. It has been shown that it is feasible to produce ceramic sheets and films with thicknesses under 200 pm. Figure 8 shows a picture of a ceramic sheet made of silicon dioxide nanoparticles. This technique could, for example, be used for the fabrication of multilayer ceramic bodies (e.g. multilayer capacitors, structural laminates) which currently are produced using the tape casting process. Big advantages relative to this conventional process would be the recycleability of the thermoplastic feedstocks and the higher achievable powder loading. 

DAP and DAIP glass laminates have high-temperature electrical properties superior to those of most other structural laminates. Cure cycles are shorter and little or no post cure is required to provide usable strength up to 482°F (250°C). 

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. 

Birley and co-workers [44,45] suggested that the stress at the gelcoat backing (structural laminate) resin interface was the most important factor in the initiation of blistering. Chen and Birley [46] classified blisters according to their origins ... 

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. 

---