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Experimental study of two-way FRP composite slab
Published in Peter J. Moss, Rajesh P. Dhakal, Progress in Mechanics of Structures and Materials, 2020
D. Huang, G.M. Van Erp, T.J. Heldt, C.L. Cattell
A prototype of the composite slab (2020 mm × 1620 mm) was constructed for the experimental study. A total of eight layers of unidirectional laminates with stacking sequence [0°/90°]4 were laminated on both sides of the 120 mm core resulting in an overall thickness of 129 mm. In this study, E-glass and vinyl ester resin were used to construct the prototype testing slab. Vinyl ester resin has advantages such as excellent chemical resistance, low viscosity, fast curing, and a good balance between mechanical properties and cost. However, the volumetric shrinkage of vinyl ester resin is in the range of 5–10%, which can cause cracking during the manufacturing process if the volume of PFR core is large. A modular manufacturing approach was adopted to overcome this exotherm problem (Huang et al. 2002). In this manufacturing approach, the shrinkage is controlled by first fabricating small element (modules) which are later combined into large assemblies. Due to the smaller volume of material involved in the modules, shrinkage is restricted to an acceptable level and does not result in cracking. In addition to the efficient control of the exotherm and shrinkage, the advantages of this modular approach also include cost effectiveness, flexibility of section shapes and suitability for both small and large structures (Huang 2004).
Pipeline Operations, Monitoring, Maintenance, and Rehabilitation
Published in Henry Liu, Pipeline Engineering, 2017
This method involves using a flexible fabric tube that can be folded (deflated) and inserted into a leaking old pipe to form a lining. By pulling the folded flexible tube into the pipe with a winch, or inverting it under fluid pressure, the tube can advance deeply into the buried pipe. Fluid pressure is used to cause the tube to inflate and attach firmly to the pipe wall. The tube, containing a thermosetting resin and a catalyst, can then be inflated by a heated fluid, such as hot water or steam. The heat causes the resin to set, forming a strong lining to protect the old leaky pipe. As it is the case with most other trenchless rehabilitation methods such as slip-lining, the pipe interior must be thoroughly cleaned and dried before inserting the fabric liner into the pipe. Types of thermosetting resin used in such linings include polyester, vinylester, and epoxy. Polyester is the most commonly used, and it has higher resistance to acids than epoxy resins do. Epoxy resins are adhesive to pipe and resistant to fluids having high pH values. Vinylester has superior corrosion resistance at high temperature. With such a lining, the pipe diameter is slightly reduced.
Matrix Materials
Published in P. K. Mallick, Processing of Polymer Matrix Composites, 2017
Vinyl ester molecules are produced by the chemical reaction of an unsaturated carboxylic acid, such as acrylic acid and methacrylic acid, and an epoxy resin (Figure 3.13). The C=C double bonds (unsaturation points) occur only at the ends of a vinyl ester molecule, and therefore, cross-linking can take place only at the ends, as shown schematically in Figure 3.13. Because of fewer cross-links, a cured vinyl ester polymer is more flexible and has a higher fracture toughness than a cured polyester resin which has a larger number of cross-links in its molecule. The presence of ester groups in vinyl ester and polyester molecules makes them susceptible to hydrolysis in the presence of water. However, since vinyl ester molecules contain fewer ester groups than polyester molecules, they have a higher resistance to degradation from water exposure. Another unique characteristic of a vinyl ester molecule is that it contains a number of OH (hydroxyl) groups along its length (Figure 3.14). These OH groups can form hydrogen bonds with similar groups on the glass fiber surface resulting in excellent wet-out and good adhesion with glass fibers.
Composite materials, technologies and manufacturing: current scenario of European Union shipyards
Published in Ships and Offshore Structures, 2023
Montserrat Dolz, Xavier Martinez, Daniel Sá, João Silva, Alfonso Jurado
The responses to the surveys and interviews have shown that almost all the shipyards use composite materials, mainly polyester, epoxy and vinylester resins, which are reinforced with fibreglass and carbon fibre. The study has also shown the percentage of implementation of each of these materials and the type of boat in which they are used. The good acceptance of these materials by shipyards allows stating that their strong impact on the shipbuilding industry will grow in the coming years as improvements in new materials and processes are brought to the market, are consolidated in it, and their price becomes more competitive. The use of these materials in shipyards will facilitate the implementation of technologies and processes to optimise manufacturing and improve the final product in the coming years.
Experimental and numerical investigation of humid ageing effects on CFRP laminates crashworthiness behaviours
Published in International Journal of Crashworthiness, 2021
Haris Ahmad Israr, King Jye Wong, Samuel Rivallant
For example, the humid ageing phenomenon can affect the laminate strength and stiffness of CFRP composite due to the plasticisation of the matrix and the degradation of the fibre/matrix interface [7–11]. Muthirakkal et al. [12] have found a clear drop of mechanical properties of carbon/epoxy materials such as 21% in flexural strength, 48% in ultimate tensile strength and 18% in inter-laminar shear strength when it absorbed moisture under humidity environment (95% RH and 70 °C) and tested in high-temperature condition. They also found the same influence of humid ageing on glass/epoxy, glass/vinylester and carbon/vinylester composites. Besides that, Cunha et al. [7] also added that the plasticisation of the matrix reduces residual stresses and increases viscoelasticity. The degradation of these material properties will influence the durability of composite materials.
Evaluation of the mechanical properties of carbon fiber/polymer resin interfaces by molecular simulation
Published in Advanced Composite Materials, 2019
Jun Koyanagi, Norie Itano, Michihiro Yamamoto, Kazuki Mori, Yuichi Ishida, Timur Bazhirov
We considered factors that underlying the difference described above. The experimentally determined interfacial strength and interfacial energy determined by MD increased in the order of vinyl ester, epoxy, and polyimide. When comparing these molecular structures, the percentage of planar sections in polyimide is the largest among these three. The planar sections likely exhibit π-π interaction [36] with the surface of the graphene which facilitates strong adsorption. In the absence of covalent bonds through interface, it is likely that π-π interactions play an important role in the interfacial interactions. Let us compare molecular structures of epoxy and vinylester. Both of them have two benzene rings and their molecular structures are similar. We surmise that a flexibility of vinylester is less significant due to lots of double bonds and epoxy has greater flexibility than that. This causes the results that molecular density near graphene of epoxy is higher than that of vinylester. Please note that this presumption is not supported by any evidence but this is one of interesting aspects which should be clarified in near future.