A Digital Twin Approach to a Quantitative Microstructure-Property Study of Carbon Fibers through HRTEM Characterization and Multiscale FEA

Abstract

Microstructures of typical carbon fibers (CFs) from polyacrylonitrile (PAN) and pitch-based precursors were studied using a novel digital twin approach with individual carbon fibers for a local crystal scale model. The transmission electron microscopy (TEM) samples were prepared using a focused-ion beam (FIB) for both longitudinal and transverse directions of carbon fibers. Measurements of the crystal size and orientation were estimated from X-ray scattering. TEM imaging of graphitic packing facilitated further comprehension of associations between processing and final material properties, which could enable customization of microstructures for property targets. Then the detailed microstructural information and their X-ray scattering properties were incorporated into the simulation model of an individual carbon fiber. Assuming that graphene properties are the same among different forms of carbon fiber, a reasonable physics-based explanation for such a drastic decrease in strength is the dislocations between the graphitic units. The model reveals critical defects and uncertainty of carbon fiber microstructures, including skin/core alignment differences and propagating fracture before ultimate failure. The models are the first to quantify microstructures at the crystal scale with micromechanics and to estimate tensile and compressive mechanical properties of carbon fiber materials, as well as potentially develop new fundamental understandings for tailoring carbon fiber and composites properties.

Advances in Insight of Radial Heterogeneous Microstructure and Its Relevance to Mechanical Properties of Polyacrylonitrile‐Based Carbon Fibers

“…In particular, the regularity of the skin and core regions showed a larger effect on the tensile properties. [ 48 ] Furthermore, the heterogeneous structure of PAN‐based CFs inevitably leads to an inhomogeneous stress distribution. This uneven stress distribution should give an explanation for the fracture rightfully.…”

“…[ 21 ] Combining HRTEM and multiscale finite element simulation, Sweat et al quantitatively analyzed the relationship between carbon fiber microstructure and properties from the crystal scale. [ 48 ] It was proposed that different regularities between the skin and core parts, different crystal sizes, dislocations, pores, and other defects are related to the mechanical properties of CFs. This finding suggests a relationship between the heterogeneous structure and the mechanical properties of carbon fibers.…”

Effect of ambient atmosphere on the formation and evolution of conjugated structure of pre-oxidized polyacrylonitrile

“…Polyacrylonitrile (PAN) based carbon fiber is an important reinforcement material to prepare the advanced fiber reinforced polymer composites and applied in different fields, such as aerospace, automation, rail transportation, marine structures and underground oil production engineering [1][2][3]. The excellent performance of carbon fiber largely depends on the pseudo graphite sheet structure generated during the graphitization process [4][5][6]. How to control the growth degree of pseudo graphite structure has become an important method to improve the mechanical and thermal properties of carbon fiber.…”