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A material is said to be frangible if through deformation it tends to break up into fragments, rather than deforming elastically and retaining its cohesion as a single object. Common crackers are examples of frangible materials, while fresh bread, which deforms plastically, is not frangible.
A structure is frangible if it breaks, distorts, or yields on impact so as to present a minimum hazard. A frangible structure is usually designed to be of minimum mass.
In order to develop international regulation for the frangibility of equipment or installations at airports, required for air navigation purposes (e.g., approach lighting towers, meteorological equipment, radio navigational aids) and their support structures,International Standards and Recommended Practices, Annex 14 (Vol. 1, section 9.9.4) to the Convention on International Civil Aviation the International Civil Aviation Organization (ICAO) initiated the "Frangible Aids Study Group" in 1981, with the task to define design requirements, design guidelines and test procedures. This work has resulted in part 6 of the Aerodrome Design Manual, dedicated to frangibility.ICAO, Aerodrome Design Manual, Part 6 - Frangibility, First Edition - 2006
An overview of the activities carried out to achieve these results is given in "Frangibility of Approach Lighting Structures at Airports".J.F.M. Wiggenraad, D.G. Zimcik, "Frangibility of Approach Lighting Structures at Airports", International Airport Review, Vol.5, No. 1 2001 The missing reference (17) in this article is in "Impact simulation of a frangible approach light structure by an aircraft wing section".J.F.M. Wiggenraad, A. de Boer, R.H.W.M. Frijns, "Impact simulation of a frangible approach light structure by an aircraft wing section", 3rd International KRASH users' Seminar, January 8–10, 2001, Arizona State University, (also available as NLR TP 2000-618) With the evolution of numerical methods suitable for impact analysis, a Chapter 6 was added to the Aerodrome Design Manual part 6, dedicated to "numerical simulation methods for evaluating frangibility". It states that numerical methods can be used to evaluate the frangibility of structures, but that the analytical models should still be verified through a series of representative field tests.
Of all equipment or installations at airports required for air navigation purposes, ICAO has not yet formulated frangibility criteria for the tower structure supporting the ILS glide path antenna, "considering its unique nature", basically: its size. A first publication on this subject is given in "Frangible design of instrument landing system/glide slope towers".M.H. van Houten, H. Gottschalk, C. Rooks, R. Miller, P. Tölke, "Frangible design of instrument landing system/glide slope towers", International Crashworthiness Conference, ICRASH2010, Leesburg, VA, USA, Sept. 22-24, 2010
Frangible bullets will disintegrate upon contact with a surface harder than the bullet itself. Frangible bullets are often used by shooters engaging in close quarter combat training to avoid ; targets are placed on steel backing plates that serve to completely fragment the bullet. Frangible bullets are typically made of non-toxic metals, and are frequently used on "green" ranges and outdoor ranges where lead abatement is a concern.
In 2024, Aspen Cooling Osberton International Horse Trials cross-country course started using frangible trakehner fences to allow the wooden fence to give way in order to prevent a horse from falling.
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