Determination of Fracture Resistance

BS 7448-4 (1997) Fracture Mechanics Toughness Tests - Part 4 Method for Determination of Fracture Resistance Curves and Initiation Values for Stable Crack Extension in Metallic Materials... 

Boccaccini, A.R., Kern, H., Dlouby, I. (2001), Determining the fracture resistance of fibre-reinforced glass matrix composites by means of the chevron-notch flexural technique , Nater, Sci. Eng., A308 (1/2), 111-117. 

Toughness assessment of ductile polymers is still a matter of debate. A sensitive way to characterise the mechanical performance of these materials, and to rank them, is to determine their ductile-brittle transitions. Test speed can thus be varied over several decades of test speed, while keeping the temperature constant, or a wide range of temperature can be scanned in controlled steps at given velocity. In the first case, the higher the speed at which the tough-to-brittle transition occurred, the better the grade in terms of fracture resistance. In the latter case, the lower the temperature at which the brittle-to-ductile transition occurred, the more suited the material for impact applications. 

Indeed, as obvious from both exemples given in Fig. 2, the transition could thus be determined accurately within 0.1-0.2 decades of test speeds with few samples in a relative short time frame. Moreover, as the apparent values (Kimax) are always lower than the effective parameters (Keff), none of the material descriptor would be overestimated. In addition, since Kjmax-values have been shown to provide a semi-quantitative evaluation (in terms of test speed or temperature) of fracture resistance parameters, a coherent material comparison would be possible over the whole investigated range. This remark remains true as long as the grades have similar rp. For iPP grades, it should be checked (and considered with more caution) when materials exhibit different particle and matrix melt flow rates, or different crystalline structures. It should also be investigated in detail when different polymer families (ABS versus HIPS or rubber modified iPP) are compared. 

The fracture resistance of a material depends on all of the properties which have been discussed including tensile strength, yield stress, elastic modulus, flexural strength, and impact resistance, all of which depend, in part, on fillers. Fillers, consequently, are important determinants of fracture resis-Only those phenomena which are related... 

The following Figures 5.8-5.10 contain further results of instrumented tensile-impact tests with the aim of determining the fracture resistance of elastomeric materials. In Figure 5.8, /d values of SBR/BR blends reinforced with various fillers and various filler contents are summarized. 

Some investigations [105-107] on micron-.size particle-filled composites demonstrated that fracture toughness is dramatically influenced by the particle shape, size, volimie fraction, and particle/matrix interfacial strength. Brunner et al. [108] reviewed the development of fracture mechanics test methods in determination of fracture toughness and delamination resistance of fiber-reinforced polymer composites. 

Plastics—Determination of the Fluidity of Plastics Using Capillary and Slit Die Rheometers Plastics—Determination of Fracture Toughness (Gc and Kq). Part 1 Linear Elastic Fracture Mechanics (LEFM) Approach Methods of Test for Volume Resistivity and Surface Resistivity of Solids Electrical Insulating Materials... 

H. Miyazaki, H. Hyuga, K. Hirao and T. Ohji, Comparison of Fracture Resistance Measured by IF MeAod and Fracture Toughness Determined by SEPB Technique Using Silicon Nitrides with Different Kficrostructures, J. Eur. Soc. Ceram., 27,2347-54 (200. ... 

Charalambides, P.G., Lund, J., Evans, A.G., McMeeking, R.M., 1989. A test specimen for determining the fracture resistance of biomaterial interfaces. J. Appl. Mech. 56, 77—82. 

Many amorphous thermoplastics are brittle, limiting their range of applications. Toughening with rubber is well known to enhance fracture resistance and toughness. Many major chemical industries are based on toughened plastics, such as ABS, HIPS and ionomers [30-34]. Important issues in the design of fracture resistant polymers are compatibility, deformation, toughening mechanisms and characterization. Particle size distribution and adhesion to the matrix must be determined by microscopy to develop structure-property relationships. 

Two major mechanisms prevail in determining the fracture resistance of polymeric materials (95). One primary contribution comes from the energy required to extend polymer chains, or some subsection thereof to the point of... 

In addition to pure modes I and II testing, there is considerable interest in determining the fracture resistance of joints subject to mixed-mode (I/n) loading as adhesive joints in engineering structures will frequently experience such mixed-mode conditions in service. There has also been a significant effort in the literature directed toward developing mixed-mode failure criteria for adhesively bonded joints, such that fracture resistance envelopes might be predicted if the resistance to the pure modes is known. 

P. G. Charalambides, J. Lund, A. G. Evans and R. M. McMeeking, A Test Specimen for Determining the Fracture Resistance of Bimaterial Interfaces, J. Appl. Mech., 56, 77- 2, 1989. "ABAQIIS User s Manuals, Version 6.11, Dassault Systemes SIMULIA Corp., Providence, Rl, 2011. 

Sulfur dioxide was the major volatile product and was used as a probe to correlate the radiation resistance with polymer structure. The use of biphenol in the polymer reduced G(SO ) by 60% compared with bisphenol A based systems (Bis-A PSF). Surprisingly, the isopro-pylidene group was shown to be remarkably radiation resistant. The ultimate tensile strain decreased with dose for all polysulfones investigated and the rate of decrease correlated well with the order of radiation resistance determined from volatile product measurements. The fracture toughness (K ) of Bis-A PSF also decreased with irradiation dose, but the biphenol based system maintained its original ductility. 

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