Abstract
Experimental work is described which examines the applicability of plane-strain fracture toughness testing techniques to several polymers. The fracture behaviour of five polymers was studied using pre-notched test specimens and was characterized by the linear elastic fracture parameter,K c. Two test geometries and loading modes were used; SEN tension and three-point bending have been investigated by varying both thickness and width. It has been established that the ASTM criterion for plane-strain conditions ofB>2.5 (K c1/σ y)2 is sufficient for SEN bending but not for tension where an extrapolation method is needed. For width effects the BCS model was shown to describe the observations and this with a limiting nominal stress analysis gave quite close agreement with the ASTM criterionW>5 (K c1/σ y)2. This value was shown to be a good estimate of the practical minimum width. There is some evidence that PP, which gives substantial crazing and whitening, can give satisfactory values at sizes about half these limiting values.
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Abbreviations
- a :
-
crack length
- B :
-
specimen thickness
- B min :
-
minimum specimen thickness
- G c :
-
strain energy release rate
- ė :
-
strain rate
- K :
-
stress intensity factor
- K c :
-
critical stress intensity factor
- K c1 :
-
plane-strain fracture toughness
- K c2 :
-
plane-stress fracture toughness
- M :
-
bending moment
- P :
-
fracture load
- r p :
-
plastic zone size
- r p2 :
-
plastic zone size in plane-stress
- S :
-
span
- T :
-
temperature
- W :
-
specimen width
- W min :
-
minimum specimen width
- \(\dot x\) :
-
cross-head speed
- y :
-
finite width correction factor
- σ :
-
stress
- σ c :
-
fracture stress
- σ N :
-
net section stress
- σ pc :
-
gross stress at plastic collapse
- σ y :
-
yield stress
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Hashemi, S., Williams, J.G. Size and loading mode effects in fracture toughness testing of polymers. J Mater Sci 19, 3746–3759 (1984). https://doi.org/10.1007/PL00020112
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DOI: https://doi.org/10.1007/PL00020112