Stress-Rupture of S-Glass Epoxy Multifilament Strands

Abstract

The stress-rupture behavior of filamentary composites is of great concern in many long-term applications. We have begun a program to collect reliable stress-rupture data on very simple composites such as various fiber strands impregnated with an epoxy matrix. We de veloped a tensile test method for fibers, designed a stress-rupture test apparatus and verified its performance, and installed 400 test apparatuses in a controlled-environment building. This paper dis cusses the data collected to date on single-end S-glass/epoxy strands at three load levels: 83.8, 74.5, and 65.2% (based on the average breaking load). Using at least 100 specimens at each load level, we found that the time-to-break values consistently varied by a factor of 1000. The data clearly indicate a shorter life at higher loads. We are collecting data at three lower load levels: 50, 40, 33%. We are attempting to characterize the distribution function of the stress- rupture life but are not yet able to draw any conclusions.

A new phenomenological creep residual strength model for the life prediction of the laminated composites

“…Glaser et al and Chiao and Moore 46,48 tested Kevlar/ epoxy and S-glass/epoxy strands at each sustained stress to the rupture time. Figure 10, known as the S-t diagram, shows the creep life experimental data of Kevlar/epoxy and S-glass/epoxy composite strands provided by Chiao et al 46,48 In Figure 10, the markers represent the scale parameter of Weibull distribution of rupture time data, and the bars show a 5-95% probability of failure. The nature of lifetime data is statistical, so the Weibull distribution function was commonly used by researchers 46,48,57,58 to describe lifetime data.…”

“…It is shown that the normalization method is capable of accumulating the residual strength data of tested T300/L20 carbon/epoxy unidirectional laminates under arbitrary stress states and sustained times in a limited area, which is successfully predicted with a single power-law equation. In addition, model predictions for different material systems are evaluated by comparing the available experimental data reported by Chiao et al for Kevlar/epoxy 45,46 and S-glass/ epoxy 47,48 strands.…”

Designing for impact resistance with unidirectional fiber composites

“…For the transverse ranking equation (6) w a s used in conjuncIt is interesting to note in table VI that one of the hybrid composites had larger impact resistance than either of the two constituent composites. hybrid composite had m o r e delaminated surfaces.…”

Estimation of creep strain and creep failure of a glass reinforced plastic by semi-analytical methods and 3D numerical simulations

“…The model presented in this article has several limitations compared to other models in the literature. It has been mentioned that it does not account for the statistical variability of the strength of fibers [44,45] and the effect of moisture on the stress corrosion cracking of glass fibers [46,51] is ignored. Moreover, this model does not describe the progressive rupture of the fibers until the final rupture of the specimen: models have been designed to investigate damage phenomena [23,24], by including damage in the matrix or debonding.…”

“…A fiber is considered as brittle, and a maximum stress criterion is defined to describe its failure [24]. The large variability in strength found in brittle fibers [44] is well modeled by Weibull-Poisson statistics and is due to various random flaws on the fiber surface [45]. Moreover, the strength of glass fibers is a function of time when subject to permanent loads [46] : moisture ingress in glass fiber reinforced polymers increases stress corrosion cracking in the fibers [47,48,49,50,51] and thus shortening their lifetime in humid or alkali environments [52,53].…”