Fracture Mechanics


The fracture mechanics assumes that the breakage of a component and, therefore, of a material occurs as a result of the propagation of cracks. It investigates the conditions of crack propagations and makes it possible to establish quantitative correlations between the outer load, i.e. the nominal stress acting in specimens or components, the size or geometry of the initial cracks as well as the resistance of the material against crack propagation.

Depending on whether the material behaviour is linear-elastic or is subject to flowing, appropriate concepts and methods for the fracture-mechanical evaluation of the crack propagation behaviour have to be chosen. For polymer materials, the linear-elastic fracture mechanics (LEFM) with small-scale yielding, the elastic-plastic fracture mechanics (EPFM) and the fracture mechanics at large plastic deformations (Post Yield Fracture Mechanics (PYFM)) are of particular importance.

The loading rate for evaluation of the crack growth behaviour can be quasi-static or dynamic. For determining the geometry-independent fracture-mechanical material parameters, we offer to you many material tests under quasi-static and impact load.

The crack growth behaviour of polymer materials is very sensitive towards structural changes in the material and therefore allows for instance an evaluation of material modifications, fibre-matrix coupling, impact modifications or ageing.

The fracture-mechanical material values characterise for polymers the resistance against unstable crack propagation or stable crack initiation and crack propagation (R-curves).

The determination of fracture-mechanical values as a function of the temperature enables the evaluation of the brittle-to-tough transition of a polymer.

We are happy to advise you on the choice of the appropriate method and standard for your material and your questions.


Quasi-static Loading

  • Method of the Essential Work of Fracture (EWF) for the determination of the significant and non-significant fracture work in films and thin specimens
  • Determination of the critical stress intensity factor or the energy release rate under 

    • bending load
    • tensile load
  • Determination of fracture-mechanical material parameters under Mode I, Mode II or Mixed Mode

    Impact Load

    • With the instrumented Charpy impact test (ICIT)
    • With the instrumented tensile impact test (ITIT)

    Methods for the Evaluation of the Resistance against Unstable Crack Propagation

    • Instrumented Charpy impact test (ICIT)
    • Determination

      • of the critical stress intensity factor (fracture toughness) Kc, Kd
      • of the critical crack opening displacement δc, δd
      • of the critical J integral Jc and Jd respectively, for example with the evaluation method of Sumpter and Turner or Merkle and Corten
      • of the critical energy release rate Gc
    • Determination of the fracture-mechanical material values under Mode I, Mode II or Mixed Mode
    • Application of the Vu-Kanh method

    Methods for the Evaluation of the Resistance against Stable Crack Initiation and Propagation (R-curves)

    • With the instrumented Charpy impact test (ICIT)
    • On Single-Edge-Notched Bend specimen (SENB specimen)
    • On Compact Tension specimen (CT specimen)
    • Determination
      • of the J-integral at the physical and technical crack initiation point
      • of the Tearing Modulus TJ as a value for the crack propagation resistance
      • of the crack-tip-opening displacement (impact)
      • Application of the EWF method for determination of the significant and non-significant fracture work in films and thin specimens

      Accredited Standards and Test Procedures

      • MPK-Procedure MPK-ICIT:
        Testing of Plastics – Instrumented Charpy Impact Test (ICIT) – Procedure for Determining the Crack Resistance Behaviour Using the Instrumented Impact Test Part
        • Part I: Determination of Characteristic Fracture Mechanics Parameters for Resistance against Unstable Crack Propagation
        • Part II: Determination of Characteristic Fracture Mechanics Parameters for Resistance against Stable Crack Propagation
      • MPK-Procedure MPK-ITIT:
        Testing of Plastics – Instrumented Tensile-Impact Test (ITIT) – Procedure for Determining the Crack Resistance Behaviour Using the Instrumented Tensile-Impact Test
      • ISO 13586:
        Plastics – Determination of Fracture Toughness (GIC and KIC) – Linear Elastic Fracture Mechanics (LEFM) Approach
      • ISO 13586 AMD 1:
        Plastics – Determination of Fracture Toughness (GIC and KIC) – Linear Elastic Fracture Mechanics (LEFM) Approach – Amendment 1: Guidelines for the Testing of Injection-Moulded Plastics Containing Discontinous Reinforcing Fibres
      • ASTM D 6068:
        Standard Test Method for Determining J-R Curves of Plastic Materials
      • Standard Draft ESIS TC4:
        A Testing Protocol for Conducting J-Crack Growth Resistance Curve Tests on Plastics

      Other Standards and Test Procedures

      • ISO 15114:
        Fibre-reinforced Plastic Composites – Determination of the Mode II Fracture Resistance for Unidirectionally Reinforced Materials using the Calibrated End-loaded Split (C-ELS) Test and an Effective Crack Length Approach
      • ISO 17281:
        Plastics – Determination of Fracture Toughness (GIC and KIC) at Moderately High Loading Rates (1 m/s)
      • ISO 15024:
        Fibre-reinforced Plastic Composites – Determination of Mode I Interlaminar Fracture Toughness, GIC, for Unidirectionally Reinforced Materials
      • ASTM D 7905/D 7905M:
        Standard Test Method for Determination of the Mode II Interlaminar Fracture Toughness of Unidirectional Fiber-Reinforced Polymer Matrix Composites
      • ASTM D 5045:
        Standard Test Methods for Plane-Strain Fracture Toughness and Strain Energy Release Rate of Plastic Materials
      • ASTM D 6671/D 6671M:
        Standard Test Method for Mixed Mode I-Mode II Interlaminar Fracture Toughness of Unidirectional Fiber Reinforced Polymer Matrix Composites
      • ASTM D 5528:
        Standard Test Method for Mode I Interlaminar Fracture Toughness of Unidirectional Fiber-Reinforced Polymer Matrix Composites
      • ASTM E 1922:
        Standard Test Method for Translaminar Fracture Toughness of Laminated and Pultruded Polymer Matrix Composite Materials
      • JIS K 7086:
        Testing Methods for Interlaminar Fracture Toughness of Carbon Fibre Reinforced Plastic

      Contact

      Dr. Ralf Lach
      Telefon: +49 (0)3461 30889-67
      ralf.lach@psm-merseburg.de

      Prof. Dr. Ines Kotter
      Telefon: +49 (0)3461 30889-70
      ines.kotter@psm-merseburg.de

      Standards

      • ISO 15114
      • ISO 13586
      • ISO 13586 AMD 1
      • ISO 17281
      • ISO 15024
      • ASTM D 7905/D 7905M
      • ASTM D 5045
      • ASTM D 6671/D 6671M
      • ASTM D 5528
      • ASTM D 6068
      • ASTM E 1922
      • JIS K 7086
      • Standard Draft ESIS TC4
      • MPK-Procedure MPK-ICIT Part I + II
      • MPK-Procedure MPK-ITIT