Accelerated Determination of the S-N Curve for Fiber-reinforced Composites Using a Quasistatic Tri-modal Tensile Test System

Abstract

Fatigue is one of the dominant modes of structural failure in materials across a wide spectrum of applications, from renewable-energy systems, transportation, and medical implants to the emerging category of flexible electronic devices. Yet, structural design for fatigue safety still lacks a reliable alternative for the conventional fatigue test, which demands numerous specimens and a vast number of loading cycles, making it very time- and cost-intensive, as well as resource-inefficient. In this study, we introduce a multiphysics material testing system, named the Tri-modal tensile test (T³) system, capable of estimating the S-N curve of fiber-reinforced composites with just a single uniaxial tensile test. This testing system is built upon a uniaxial tensile test of Carbon nanotube-doped Glass fiber reinforced polymer (GFRP), during which changes in the internal damage state for the entire stress-strain levels are closely monitored through infrared thermography and electrical resistance measurements. The multiphysics signals obtained from the T³ system are analyzed using damage and fatigue-related theories to derive a reliable estimation of the S-N curve. Then, we validate the proposed system by comparing the S-N curves estimated with the T³ system to actual data points obtained from conventional fatigue tests, across three composite configurations featuring different laminate sequences: quasi-isotropic, angle-ply, and unidirectional. Results showed that the S-N curves estimated with our T³ system align closely with the actual fatigue test results, highlighting the potential of the T³ system as an accelerated and reliable method for evaluating the S-N curve of composite materials.