National Academies Press: OpenBook

Use of Fiber-Reinforced Polymers in Highway Infrastructure (2017)

Chapter: Chapter Three - Manufacturing Techniques

« Previous: Chapter Two - Fiber-Reinforced Polymer Materials
Page 12
Suggested Citation:"Chapter Three - Manufacturing Techniques." National Academies of Sciences, Engineering, and Medicine. 2017. Use of Fiber-Reinforced Polymers in Highway Infrastructure. Washington, DC: The National Academies Press. doi: 10.17226/24888.
×
Page 12
Page 13
Suggested Citation:"Chapter Three - Manufacturing Techniques." National Academies of Sciences, Engineering, and Medicine. 2017. Use of Fiber-Reinforced Polymers in Highway Infrastructure. Washington, DC: The National Academies Press. doi: 10.17226/24888.
×
Page 13

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

12 chapter three Manufacturing techniques Several manufacturing techniques are available to produce FRP composites for highway infrastruc- ture, although a number of other methods exist for mechanical or aerospace industries (Figure 2). A brief discussion is provided to describe FRP manufacturing, and further details are available in other sources dedicated to composites manufacturing such as Mazumdar (2001) and Strong (2007). • Pultrusion: the word pultrusion is derived from a combination of “pull” and “extrusion,” which can represent the process of pulling continuous fibers impregnated in a polymeric resin to form a composite shape. Because of an automated manufacturing process, pultrusion is a suitable method for the mass production of FRP profiles having constant cross-sectional dimensions at minimal costs. The size of FRP sections or bars is determined by the configuration of a preheated pultrusion die, through which the resin-impregnated fibers are pulled and cured. By adjusting the shape of the die, virtually all types of structural sections can be produced from open to closed profiles (e.g., C-channels and hollow beams) without any restriction on their length. However, it can be noted that straight products are manufactured, and curved geometries in the pulling direction may not be achievable. • Wet lay-up: the in situ impregnation of dry fiber fabrics with a resin matrix to form composite laminates or sheets is called the wet lay-up method. The fiber fabrics are mostly unidirectional (i.e., often called a 0° fiber angle), whereas multidirectional fabrics can also be employed. This approach, exclusively used to strengthen existing structural members, is a convenient means to manufacture FRP products without the use of special equipment or facilities. The wet FRP sheet is then bonded to the substrate of a structural member using an adhesive and cured at ambient temperature to increase the capacity of the member. It is important that the wet lay-up applica- tion be completed within a specific workable period prior to the hardening of the bonding agent. Either a single ply or multiple plies of FRP sheet may be used, depending on the amount of external reinforcement required to address the deficient structural capacity. Quality control is an important factor influencing the performance of strengthened members (e.g., proper bonding without entrapped air bubbles between the bonded FRP and substrate, surface preparation of the substrate, and curing conditions). • Filament winding: this manufacturing technique produces FRP tubes for structural application (e.g., concrete-filled FRP tubes as load-bearing members). Continuous fiber strands are pulled from spools, impregnated with a liquid resin matrix, and transversed along a rotating mandrel. After completing the automated filament-winding processes, the shaped impregnated fibers are cured and removed from the mandrel. This method can conveniently tailor the thickness and fiber angle of FRP composites to satisfy the requirements of various end-users. • Other techniques: although the foregoing three methods are predominantly utilized in manu- facturing FRP composites for structural applications, other approaches are available: vacuum- assisted resin transfer molding (VARTM), centrifugal casting, resin transfer molding, and compression molding. The VARTM technique can be used to manufacture FRP bridge decks. It requires open or closed molds with a vacuum bag where dry fibers are placed, and a liquid resin is gradually infused by a vacuum without air leakages. A visual inspection or vacuum pressure monitoring detects the presence of air bubbles or leakages. After squeezing out the residual resin, the impregnated fibers are cured to produce a structural composite.

13 FIGURE 2 Manufacturing process: (a) pultrusion (image courtesy of Strongwell); (b) wet lay-up [Yang et al. 2011 (used by permission from American Concrete Institute)]; (c) vacuum-assisted resin transfer molding (used by permission from Carbonbydesign). (a) (b) (c)

Next: Chapter Four - Codes, Standards, and Design Guidelines »
Use of Fiber-Reinforced Polymers in Highway Infrastructure Get This Book
×
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 512: Use of Fiber-Reinforced Polymers in Highway Infrastructure documents the current state of the practice in the use of fiber-reinforced polymers (FRPs) in highway infrastructure. The synthesis identifies FRP applications, current research, barriers to more widespread use, and research needs. The objectives of the study are to synthesize published literature on FRP materials in highway infrastructure and to establish the state of current practice of FRP applications in transportation agencies.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!