FRP laminates

Using a combination of unidirectional and/or biaxial fabrics, the laminates provide strength in both longitudinal and transverse directions. The range of the tensile strength of PipeMedic laminates is 60—155 ksi (415—1070 MPa). 

The laminates are much thinner than conventional laminate strips with a thickness as small as 0.01 in (0.25 mm), they can be easily coiled to fit a pipe with a diameter of 3 in (75 mm). 

The laminates are manufactured in plants under high-quality control standards, which improves the quality of the finished construction. 

The strength of the laminates can be tested prior to installation in contrast, when the wet layup method is used, samples are made daily in the field for future testing and any defective material will not be revealed for several days until the samples are tested this makes remedial measures difficult to implement. 

The number and pattern of the layers of fabrics in PipeMedic laminates can be adjusted to produce an endless array of customized products that can significantly save construction time and money. 

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As described earlier, there are many resin types that can be used in making an FRP laminate. The choice of resin will depend on many factors, including... 

Time, temperature, viscosity models are another useful element in understanding the science of thermoset resin processing. They perform a number of valuable functions such as defining the proper point for consolidation pressure application in FRP lamin-... 

Comparison of Interlaminar Fracture Toughness between CFRP andAI.FRP Laminates... 

Trigonal . [Akzo Akzo Chem. BV] Kettmes or benzoin ethers uv inidatoi/ sensitizer for printing inks, paper coatings, curing polyester and FRP laminates. 

Dual Laminate (Fluoropolymer-lined FRP) Same as Adhesive-bonded Fabricate liner first on a mandrel (hand and machine welding) and build FRP laminate over the liner. Use carbon cloth for spark testing Shop and Field Pressure OK (RTP-1 Dual lam) Vacuum OK for FRP/fluoropolymer bond. Design FRP for vacuum 33 dia max Visual Spark AE CRBBD Possible Testing recommended... 

The cylindrical section of the vessel is fabricated using fusion welding followed by carbon cloth and FRP laminating. 

Methods of producing FRP laminates with polyesters have been described in Chapter 2. The major process today is the hand layup technique in which the resin is brushed or rolled into the glass mat (or cloth) by hand (see Figure 2.44). Since unsaturated polyesters are susceptible to polymerization inhibition by air, surfaces of the hand layup laminates may remain under-cured, soft, and, in some cases, tacky if freely exposed to air during the curing. A common way of avoiding this difiiculty is to blend a small amount of paraffin wax (or other incompatible material) in with the resin. This blooms out on the surface and forms a protective layer over the resin during cure. 

Puck A, Schurmann H. Failure analysis of FRP laminates by means of physically based phenomenological models. Compos Sci Technol 2002 62 1633-62. 

Davila C, Camanho PP, Rose CA. Failure criteria for FRP laminates. J Compos Mater 2005 39 323-45. 

Process variability during manufacture of FRP laminates can affect delamination resistance, for example by variation of the forming temperature of CFRP thermoplastic (IM6/PEEK) laminates [71]. Lower forming temperature (-1-360 °C) yielded lower mode I and mode II delamination resistance than -1-380 °C (the recommended manufacturer value), whereas higher temperatures (-1-400 °C to 4-440 °C) resulted in improved interfacial strength with corresponding improvements in mode II delamination resistance. 

Although off-angle and some multidirectionally reinforced FRP laminates may still have fibres aligned in one single direction or orientation in each ply (and just have different fibre orientations from ply to ply), there are more complex fibre arrangements that also need to be considered. 

Currently available data indicate that 3D reinforcements typically result in high values of Gc compared with the unidirectional laminate made from the same fibre and matrix. Whether the high delamination resistance of 3D FRP laminates does represent material values or apparent values, for example depending on specific test and specimen parameters, is still debated (see e.g. Ref. [92]). More generally, the applicability of linear elastic fracture mechanics to through-thickness reinforced FRP composites is questionable [98]. 

Mechanical deterioration of FRP laminates after sea water exposure... 

Uses Initiator used in UV light curing of polyester resins UV sensitizer for lacquers and FRP laminates... 

Plevris, N. and T. C. Triantafillou (1994). Time-dependent behaviour of RC members strengthened with FRP laminates. Journal of Structural Engineering 120(3) pp. 1016-1042. 

When subjected to a uniformly distributed fire on one side, the heat transfer through the thickness direction of a plate is dominant, as compared to that in the in-plane directions. Three main zones can be defined through the thickness of an FRP laminate during decomposition ... 

Fatigue strengths should, wherever possible, he determined on the basis of tests on samples of the FRP laminate made with similar resin and glass fibre reinforcement of similar type and proportions. The conditions of the test should be appropriate to the loading conditions of the component being designed, and to the environmental conditions. 

Flowever, should the elastic hmit be reached, the lack of an appreciable ductile range in the stress—strain curve for typical FRP laminates is likely to cause failure by direct rupture or tearing, particularly at locations of stress concentration or where free movement of the laminate is prevented, such as at joints or points of connection. In stmctures which rely on flexible dynamic response to attenuate the blast loading, joints should be designed ... 

P(8) Bolt shear failure (Figure 5.11 (d)) is caused by high shear stress in the fastener. Normally the glass FRP laminate failure occurs before fastener shear failure. 

Within the EUROCOMP Programme, data for three different glass FRP laminate configurations were generated from two different material systems. The data are listed in the EUROCOMP Handbook. 

Figure 5.21 Shear stress distribution (t xz) through the thickness of the glass FRP laminate due to a tension loaded stresses.

P(5) Holes for structural connections using bolts loaded in shear shall be formed so that each bolt is a close fit in the mating holes of the parts to be joined and so that no loads due to misaligned holes are imparted to either of the FRP laminates being joined. 

Meier U et al, Strengthening of structures with Carbon FRP laminates research and applications in Switzerland In Advanced Composite Materials in Bridges and Structures (Ed K W Neale and P Labossiere), Canadian Society for Civil Engineering, Montreal, Canada, 1992. 

Drop weight tests are mainly used for quality control of sheet materials. These tests can be applied to FRP laminates and are more appropriate than Izod and Charpy tests since they allow failure criteria other than ultimate failure to be specified. 

It follows that other mechanical properties of FRP laminates will degrade at these higher temperatures. However, the retention of the mechanical properties is substantially increased as the glass content is increased. 

Table 4.40 Influence of temperature on short term flexural strength retention of FRP laminates, fabricated from several types of polyester resin (typical).

ISO Standards covering the determination of the basic properties of the FRP laminate are listed below (other tests are listed in Appendix 7.1). These cover the elastic, short term properties and may either be used for the testing of a new product or as part of the compliance testing process described in 7.2. 

The resin is an isophthalic polyester resin. Its principal advantage, besides low cost, lies in its rapid and controllable cure chemistry and therefore in its ease of use within hand lay up fabrication processes. There are several types of polyester but isophthalic resins offer the most attractive combination of mechanical properties and environmental resistance (i.e. reduced corrosion and maintenance costs, and good resistance to attack by chemicals). Moreover, previous studies on effects of immersion and weathering (exposure to wind, rain, sun) show that the performance of glass FRP laminates are generally good, especially with isophthalic polyester resin. 

Failure of a laminate under compressive load acting in the fibre direction is likely to involve microscopic buckling of individual fibres, which act as cylindrical beam-columns on an elastic foundation provided by the surrounding matrix. Compressive failure of glass FRP laminates is strongly influenced by imperfections, including ... 

Theoretical methods of evaluating moduli for glass FRP laminates are difficult to verify experimentally, partly because accurate estimates of moduli for fibre and resin constituents are seldom available and partly because of the scatter of experimental data, attributable in part to inherent material variability but possibly also to inadequate testing techniques. While no final conclusions can be drawn regarding the accuracy of the theoretical methods used, it is evident that the computed results are broadly in agreement with measured data. 

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