Mixed-mode fracture in a quasi-brittle material: R-curve and fracture criterion – Application to wood

Published Date
Engineering Fracture Mechanics
May 2016, Vol.156:96–113, doi:10.1016/j.engfracmech.2016.02.006

• Author 

• Ngoc Anh Phan
• Stéphane Morel ^,
• Myriam Chaplain

• Université de Bordeaux, UMR 5295, Institut de Mécanique et d’Ingénierie – Bordeaux (I2M), Dépt. Génie Civil et Environnemental (GCE), Bordeaux F-33000, France

Received 2 July 2015. Revised 1 February 2016. Accepted 2 February 2016. Available online 8 February 2016. 

Abstract

Mixed-Mode Bending tests are performed on spruce specimens for several mixed mode ratios and are completed by pure mode I (DCB) and pure mode II (ENF) fracture tests. For each test, the mixed mode resistance to crack growth and those relative to its mode I and mode II components are estimated. The separation of the fracture modes is estimated from an analytical formulation and verified from the invariant  -integral method. A mixed mode fracture criterion applicable to the overall R-curve (i.e., rising part and plateau regime) is then proposed and allows describing the mixed mode resistance with a reasonable accuracy.

Keywords

Mixed-Mode Bending

Equivalent LEFM

R-curve

Fracture criteria

-integral

Wood

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Nomenclature

a

Eq. LEFM crack length

initial notch length

Eq. LEFM crack length increment

mixed mode specimen compliance

mixed mode energy release rate

mode I component of the mixed mode energy release rate

mode II component of the mixed mode energy release rate

mixed mode resistance to crack growth

mode I component of the mixed mode resistance to crack growth

mode II component of the mixed mode resistance to crack growth

plateau resistance of the mode I component of the mixed mode resistance to crack growth

plateau resistance of the mode II component of the mixed mode resistance to crack growth

mode I resistance to crack growth

mode II resistance to crack growth

Eq. LEFM length of the FPZ (onset of the plateau resistance regime)

c

loading lever

multiplicative correction factor

Fig. 1.

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 Table 1

Table 1.

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 Table 2

Table 2.

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Fig. 9.

 Table 3

Table 3.

 Table 4

Table 4.

Fig. 10.

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Fig. 14.

• ⁎ 
  Corresponding author.
  
  

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