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ASTM standard provides testing for interlaminar fracture toughness

News International-French

27 Nov 2014

This standard is about test method for determination of the mode II interlaminar fracture toughness of unidirectional fiber-reinforced polymer matrix composites using the end-notched flexure (ENF) test.

Laminated composite materials are everywhere and interlaminar cracks can cause serious damage to many types of structures and products, from sports equipment to spacecraft:

  • Sporting goods, including tennis rackets, golf clubs and skis
  • Electronics, including many circuit boards
  • Civil infrastructure, including bridge decking, gas pipelines and beams and columns in buildings
  • Automotive structure, body panels and interiors
  • Airplanes, helicopters and spacecraft

While fracture toughness tests exist for mode I and mixed-mode, no test currently exists for mode II.

The mode II test described in ASTM D7905/D7905M will be used by industry and government for qualitatively comparing composite materials as well as determining values to be used in design, analysis and acceptance/rejection criteria.

That delaminations can occur in several different ways: during manufacture, from damage during usage, from unexpected overloads of a structure or simply from normal service loadings over extended periods of time.

“Delamination growth represents a critical failure mode in structures fabricated from fiber reinforced polymer matrix composites, so there is a concerted effort in the community to develop the tools and techniques to make sure that this does not occur,” says ASTM member Barry D. Davidson. Determining a material’s resistance to delamination growth is a key component to this work.

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