In materials science, fracture toughness (KIc) refers to the ability of a material containing a crack to resist fracture. Specifically, fracture toughness testing characterizes resistance to fracture in a neutral environment with a sharp crack, and is one of the most important properties of any material for virtually all design applications. 

Fracture mechanics testing derives a value that can be used in design work to ensure that the fabrication does not fail by brittle fracture. It can also be used to determine life (or remaining life) of a material in fatigue or corrosion testing. 

Because of the complex nature of cracking and fracture resistance, there are multiple physical properties that contribute to a material’s fracture toughness value. Element offers a suite of testing, so you can be certain of your material’s abilities and limitations. 

ASTM D3039 Composite Tensile Testing
Fracture Toughness

Testing for K1C

The KIC test (sometimes referred to as KIC, or K1C) is used to determine the fracture toughness of metallic materials. This test is in direct contrast with Charpy Impact Toughness, which can only be used to compare the notch toughness of materials or determine a metal’s compliance with a specification. Most often associated with ASTM E399, the Linear-Elastic Plane Strain Fracture Toughness test, or KIc value, can be used directly, across a range of temperatures, to determine design, life calculations and crack growth, or remaining life calculations.

Tensile Testing Laboratory
Fracture Toughness

Testing for CTOD

Crack Tip Opening Displacement, or CTOD, is a measure of the physical opening of the fatigue crack tip at the point of failure. Typically used to measure the toughness of materials that tear before failure, all tests can be carried out from -129ºC (-200ºF) to 200ºC ( 400ºF). 

Mechanical Testing Aerospace Product Lifecycle
Fracture Toughness

Testing for J1C and JR Values

Unlike K1C, a material’s J1C value is used to determine toughness using the energy required to fracture the sample. A related value, JR, uses one or more samples to determine the initial point of tearing. 

Element fracture toughness experts can assist in projects ranging from single materials to complex systems. For more information on brittleness and toughness testing, or to request a quote, contact an expert today.

Fracture Toughness

Standards We Test To

American Petroleum Institute

API 1104

American Society for Testing & Methods

ASTM E399, ASTM E1820, ASTM B645, ASTM B646, ASTM E561, ASTM E1304, ASTM D7905, ASTM D5528, ASTM D6671, ASTM E370

British Standards

BS 7448, BS 8571

Det Norske Veritas


International Standards Organization

ISO 12135, ISO 12737, ISO 15653


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