FRP composites

The lack of homogeneity and the friable nature of FRP composite structures dictate that caution be followed in mechanical design, vendor selection, inspection, shipment, installation, and use. 

Myriad FRP products are available for either the repair or the outright replacement of existing structures. In addition to chemical-process pipes and tanks, FRP composite products include structural shapes, bridge systems, grating, handrail ladders, etc. 

FIGURE 20.9 Comparison of measured and modeled (FDS5) HRR forrail carmockup. (Adapted from Coles, A. et al., Using computer fire modeling to reproduce and predict FRP composite fire performance, in Composites Polycon 2009, American Composites Manufacturers Association, Tampa, FL, January 15-17, 2009.)... 

Stevens, M., How does laminate construction affect fire performance of FRP composites, Proceedings of Composites and Polycon, Tampa, FL, October, 2007. 

Fibre reinforced plastic (FRP) composites are gaining a wide reeognition as an alternative to the traditional metallic materials in a variety of applieations. As a result a reasonable step is to understand the mechanics of composites and provide the designers and industry with the knowledge based on reliable data stemmed from extensive researeh. 

Brunner A.J., Nordstrom, R.A., Fliieler, P., (1997), Fracture Phenomena Characterization in FRP-Composites by Acoustic Emission , Proceedings European Conference on Macromolecular Physics Surfaces and Interfaces in Polymers and Composites, EPS Vol. 21B, pp. 83-84, European Physical Society. 

Fracmre mechanics tests that quantify the delamination resistance of FRP composites determine the rate of change in strain energy per unit area of delamination (i.e. the... 

Strain energy release rate, which is the driving force for delamination propagation and denoted by the symbol G) [1,4]. Assessment of the long-term performance of FRP composites for aerospace apphcations requires consideration of the effects on their delamination resistance of both service loads and environmental exposure. 

This chapter will first discuss fracture mechanics applications to polymer composites in aerospace, and then compile the different test methods by type of load. The industiy-specific fracture mechanics test procedures for FRP composites, such as the Airbus Industries Test Method (AITM) or Boeing Support Specification (BSS), are essentially based on test procedures developed by national or international standardization agencies. This will be followed by a section with literature data to highlight selected effects of processing and material layup and type. Further sections will discuss non-unidirectional reinforcement and testing under environmental conditions that are relevant to aerospace applications, and the chapter concludes with an outlook on materials and test development trends. 

Applications of fracture mechanics of fibre-reinforced polymer-matrix (FRP) composites in aerospace... 

Use of fracture mechanics test methods for failure analysis of FRP composite elements is feasible, but to the best knowledge of the author, no examples of this have been published. The challenge here is mainly the preparation of suitable test specimens from structural elements and the creation of the starter cracks. ISO 15024 does provide some information on mode I starter crack preparation for nonstandard specimens in an informative appendix (B.8, Guidelines for wedge precracking ), and that procedure can be adapted for other specimen geometries. 

A summary of quasi-static delamination test methods for continuous-fibre, unidirectional FRP composites is given in Table 8.1. For mode 1, several standard test methods exist, namely, JIS K7086 ( Testing methods for interlaminar fracture toughness of carbon fibre reinforced plastics , 1993) this also includes a quasi-static mode 11 standard test, ASTM... 

Table 8.1 Quasi-static fracture mechanics test methods for FRP composites...

The literature published on fracture mechanics testing of FRPs in the last 40 years comprises a large database on delamination resistance or fracture toughness of different types of FRPs. An early review [51] compiled the data available at that time. Selected data from quasi-static mode I and mode II tests on FRPs were compared by O Brien [52], and quasi-static mode I test data from carbon—fibre epoxy and poly-ether-ether-ketone (PEEK) by Brunner [53]. Mechanical properties of FRP composites are compiled in the Composite Materials Handbook version F (2002) [9—11], but this does not comprise fracture mechanics data. Hence, there is no comprehensive and up-to-date database on the available data or literature. 

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