Analysis of Defects in Poly(ethylene terephthalate) Fibers (original) (raw)
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Generalized Stress Intensity Factor at the Corner of Debonded Fiber Ends
Journal of the Society of Materials Science, Japan, 2008
This paper deals with intensity of singular stress field at the corner of debonded ends of an elastic cylindrical inclusion in an infinite body under tension. The problem is formulated as a system of singular integral equations, where unknown functions are densities of body forces distributed in infinite bodies having the same elastic constants as those of matrix and inclusion. In the numerical analysis, the unknown function of the body force densities are expressed as a linear combination of two types of fundamental density function and power series, where the fundamental density functions are chosen to express the symmetric stress singularity of the from r λ1−1 and the skew-symmetrics stress singularity of the from r λ2−1. Then, generalized stress intensity factors, which control the singular stress fields at the end of the cylindrical inclusion are discussed with varying the fiber lengths and elastic modulus ratio. The effect of debonding length on the generalized stress intensity factors is also discussed in comparison with the results of a cylindrical cavity. The results are also compared with ones for a rectangular inclusion.
Nihon Reoroji Gakkaishi, 2014
We studied the dependencies of material properties on several types of average molecular weight for a recycled high density polyethylene that was obtained from PET-bottle caps. We discussed the correlations of the average molecular weights with the density, melt index, high load melt index, yield stress, and elongation at break. We concluded that these material properties of the recycled HDPE are similar to those of the virgin HDPE with the identical average molecular weight.
2022
Carbon fiber is a brittle material and its tensile strength is strongly influenced by defects, which are often assessed by the shape parameter of the Weibull distribution. Therefore, the shorter the gauge length is, the higher the tensile strength is. The usual tensile test is conducted with a gauge length of 25 mm and the tensile strength at short gauge is derived using Weibull distribution. However, it is reported that the shape parameter changes when the gauge length is less than 1mm. The objective of this work is to attempt to evaluate the short gauge tensile strength of carbon fiber in tests under optical microscope observation. The shorter the gauge length was, the more test results of fiber separation from adhesive or fiber breakage in adhesive were observed. It is found that the test of short gauge of 0.2 mm requires careful specimen preparation to avoid shear stress due to misalignment of fiber and loading axes. Weibull shape parameters of the tensile strengths at the gauges from 50mm to 1mm were almost the same as the usual tensile test. However, the values for the 0.5 mm and 0.2 mm gauges were higher than those for the longer gauges.
Dependencies of Material Properties on Molecular Weight Distribution of Industrial Polyethylenes
Nihon Reoroji Gakkaishi, 2008
We studied the dependence of material properties on molecular weight distribution (MWD) of polymers using highdensity-polyethylenes (without short branch chain) with a wide range of molecular weights and known MWD. We discussed the correlations of harmonic-, the arithmetic-, and geometric-mean of MWD with each material properties of melt index, high load melt index, elongation at break, failure point, density, Charpy impact residence, and yield stress. The former four properties were governed by the arithmetic mean of MWD whereas the latter three properties were controlled by the geometric mean of MWD.