Influence of Hysteresis on Tensile and Fatigue Failure in Rubbers

1972 ◽  
Vol 45 (4) ◽  
pp. 1043-1050 ◽  
Author(s):  
A. R. Payne ◽  
R. E. Whittaker
Keyword(s):  
Fatigue Failure ◽  
Failure Criterion ◽  
Energy Input ◽  
Flaw Size ◽  
Fatigue Properties ◽  
Growth Constant ◽  
Fine Particulate ◽  
Growth Properties ◽  
Tearing Energy ◽  
Energy Theory

Abstract The failure criterion developed by Harwood et al. between energy input to break and hysteresis at break for amorphous rubbers has been related to the fatigue and cut growth properties of the rubber which are based on the tearing energy theory. It is found that the constant K in the hysteresis failure criterion is a function of the cut growth constant G and the inherent flaw size C0. The effect of adding fine particulate fillers to amorphous rubbers on the hysteresis and fatigue properties is considered and shown to be in agreement with the theory.

Effect of Crosslink Density on the Critical Flaw Size of a Simple Elastomer

1983 ◽  
Vol 56 (1) ◽  
pp. 244-251 ◽  
Author(s):  
G. R. Hamed
Keyword(s):  
Crosslink Density ◽  
Unit Volume ◽  
Crack Tip ◽  
Flaw Size ◽  
Critical Flaw ◽  
Tearing Energy ◽  
Energy Theory ◽  
Crosslink Densities

Abstract Tensile experiments have been carried out on a gum, amorphous EPDM elastomer. Samples with various crosslink densities and containing precuts of different lengths were tested. The energy, Wb, per unit volume, to fracture a specimen varied inversely with the length of the precut as predicted by simple tearing energy theory. Values of the inherent flaw size, Co, of the samples were determined by extrapolation of Wb to that value obtained when no intentional precut was present. Values of Co decreased with increasing crosslink density. This illustrates the decreasing ability of an elastomer network to blunt the crack tip of a stress-raising flaw as crosslinking is increased. It is suggested that this phenomenon is at least partly responsible for low values of Wb at high crosslink densities.

Cut Growth and Fatigue of Rubbers. II. Experiments on A Noncrystallizing Rubber

1965 ◽  
Vol 38 (2) ◽  
pp. 301-313 ◽  
Author(s):  
G. J. Lake ◽  
P. B. Lindley
Keyword(s):  
Natural Rubber ◽  
Fatigue Failure ◽  
Fatigue Behavior ◽  
Time Dependent ◽  
Fourth Power ◽  
Dynamic Conditions ◽  
Tensile Fatigue ◽  
Different Temperatures ◽  
Tearing Energy ◽  
Energy Theory

Abstract Tensile fatigue failure of a gum vulcanizate of noncrystallizing SBR can be accounted for by the growth of small flaws initially present in the rubber. Fatigue of crystallizing natural rubber was shown in Part I to be attributable to the same cause. Cut growth results are interpreted in terms of the tearing energy theory of Rivlin and Thomas. SBR exhibits cut growth under both static and dynamic conditions; in each case the rate is approximately proportional to the fourth power of the tearing energy. Variation of the dynamic cut growth rate with frequency can be explained by the summation of a time-dependent static component of growth and a cyclic component not dissimilar to that occurring in natural rubber. Fatigue failure, under both static and dynamic conditions, is predicted from the cut growth results. These predictions are found to account quantitatively for experimentally observed fatigue lives when a suitable value is assumed for the initial flaw size. Fatigue lives at different temperatures correlate well with cut growth results obtained by Greensmith and Thomas over the same temperature range. The results are compared to those obtained previously for natural rubber, and possible reasons for the differences in fatigue behavior of crystallizing and non-crystallizing rubbers are discussed.

A Note on the Shear Stress Criterion for Fatigue Failure under Combined Stress

1969 ◽  
Vol 20 (1) ◽  
pp. 57-60 ◽  
Author(s):  
R. E. Little
Keyword(s):  
Shear Stress ◽  
Fatigue Limit ◽  
Fatigue Failure ◽  
Failure Criterion ◽  
Basic Problem ◽  
Failure Criteria ◽  
Test Methods ◽  
Combined Stress ◽  
Stress Criterion

SummaryNishihara’s combined bending and torsion out-of-phase fatigue limit data are analysed. The Tresca shear stress failure criterion predicts strengths up to 30 per cent higher than observed. It thus appears that renewed attention should be given to the basic problem of developing reliable combined stress failure criteria. It is suggested that new test methods will be required for this purpose.

scholarly journals Investigation of creep and fatigue in high temperature polymer matrix composites using a micromechanical approach

2021 ◽  
Author(s):  
Alireza Sayyidmousavi
Keyword(s):  
High Temperature ◽  
Fatigue Failure ◽  
Polymer Matrix ◽  
Failure Criterion ◽  
Failure Modes ◽  
Polymer Matrix Composites ◽  
Matrix Composites ◽  
Difficult Situation ◽  
Strain Evolution ◽  
Micromechanical Approach

Polymer matrix composites (PMC’s) are widely used in critical aerospace structures due to their numerous advantageous mechanical properties. Recently, PMC’s have been considered for high temperature applications where viscoelasticity arising from the time dependent nature of the polymer matrix becomes an important consideration. This inherent viscoelasticity can significantly influence deformation, strength and failure response of these materials under different loading modes and environmental factors. With a potentially large number of plies of different fiber directions and perhaps material properties, determining a fatigue failure criterion of any degree of generality through experiments only, may seem to be an unrealistic task. This difficult situation may be mitigated through the development of suitable theoretical micro or macro mechanical models that are founded on considering the fatigue failure of the constituting laminas. The micro‐approach provides a detailed examination of the individual failure modes in each of the constituent materials i.e. fiber, matrix. In this work, a micromechanical approach is used to study the role of viscoelasticity on the fatigue behavior of polymer matrix composites. In particular, the study examines the interaction of fatigue and creep in polymer matrix composites. The matrix phase is modeled as a vicoelastic material using Schapery’s single integral constitutive equation. Taking viscoelsticity into account allows the study of creep strain evolution during the fatigue loading. The fatigue failure criterion is expressed in terms of the fatigue failure functions of the constituent materials. The micromechanical model is also used to calculate these fatigue failure functions from the knowledge of the S‐N diagrams of the composite material in longitudinal, transverse and shear loadings thus eliminating the need for any further experimentation. Unlike the previous works, the present study can distinguish between the strain evolution due to fatigue and creep. The results can clearly show the contribution made by the effect of viscoelasticity to the total strain evolution during the fatigue life of the specimen. Although the effect of viscoelsticity is found to increase with temperature, its contribution to strain development during fatigue is compromised by the shorter life of the specimen when compared to lower temperatures.

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