Hierarchical Mechanisms of Lateral Interactions in High-Performance Fibers

Abstract

The processing conditions used in the production of advanced polymer fibers facilitate the formation of an oriented fibrillar network that consists of structures spanning multiple length scales. The irregular nature of fiber tensile fracture surfaces suggests that their structural integrity is defined by the degree of lateral (interfacial) interactions that exist within the fiber microstructure. To date, experimental studies have quantified interfacial adhesion between nanoscale fibrils measuring 10−50 nm in width, and the global fracture energy through applying peel loads to fiber halves. However, a more in-depth evaluation of tensile fracture indicates that fiber failure typically occurs at an intermediate length scale, involving fibrillation along interfaces between fibril bundles of a few 100s of nanometers in width. Interaction mechanisms at this length scale have not yet been studied, due in part to a lack of established experimental techniques. Here, a new focused ion beam-based sample preparation protocol is combined with nanoindentation to probe interfaces at the intermediate length scale in two high-performance fibers, a rigid-rod poly(p-phenylene terephthalamide) and a flexible chain ultrahigh molecular weight polyethylene fiber. Higher interfacial separation energy recorded in the rigid-rod fiber correlated with less intensive fibrillation during failure and is discussed in the context of fiber chemistry and processing. Power law scaling of the total absorbed interfacial separation energy at three different scales in the polyethylene fiber is observed and analyzed, and distinct energy absorption mechanisms, featuring a degree of self-similarity, are identified. The contribution of these mechanisms to the overall integrity of the fiber is discussed, and the importance of the intermediate scale is elucidated. Results from this study provide new insights into the mechanical implications of hierarchical lateral interactions and will aid in the development of novel fibers with further improved mechanical performance.

Effect of the Fiber Treatment on the Stiffness of Date Palm Fiber Reinforced PP Composites: Macro and Micromechanical Evaluation of the Young’s Modulus

“…Fiber bundles are composed of single fibers and the interface between such fibers, mainly lignin and hemicellulose. Thus, the same mechanisms of load transferring observed in the composite between the matrix and the reinforcement, are repeated inside the reinforcement at other scale [54]. The short deformations used to measure the Young's modulus prevent the failure of the matrix-fiber interface and also of the fiber-fiber interface.…”

Structure and properties of gel‐spun ultra‐high molecular weight polyethylene fibers obtained from industrial production line

“…With the rapid development of industry and technology, high‐performance fibers applied to many fields ranging from civil materials to military aviation basic materials have gained immense importance of mankind 1,2 . Interestingly, among various high‐performance fibers, the one with the highest specific modulus and strength are consist of the simplest polymer molecule of polyethylene (PE), 3 due to the advantages of intrinsic molecular strength and the formation of highly oriented hierarchical microstructure 1,4,5 .…”

“…With the rapid development of industry and technology, high‐performance fibers applied to many fields ranging from civil materials to military aviation basic materials have gained immense importance of mankind 1,2 . Interestingly, among various high‐performance fibers, the one with the highest specific modulus and strength are consist of the simplest polymer molecule of polyethylene (PE), 3 due to the advantages of intrinsic molecular strength and the formation of highly oriented hierarchical microstructure 1,4,5 . Ultra‐high molecular weight polyethylene (UHMWPE), as one of the synthetic advanced polymer fibers with a viscosity average molecular weight ranging from 1.5 to 8 million, possesses excellent properties of high cut resistance, low water absorption and high resistance to low temperature.…”

“…And they found that the improvement of fiber properties could be using poor solvents or crystallization under low undercooling at a given concentration. The intermediate length scale and the molecular features of UHMWPE fibers was investigated, and proposed a multiscale structural model that described the organization of molecules from the unit cell to the filament level 1,3 . The rheological response of partially entangled UHMWPE chains both in and out of equilibrium in the tube model was also investigated by researchers 19 .…”

The effect of shrinkage on the structure and properties of ultra‐high molecular weight polyethylene fibers with different concentration

“…The high tensile strength and high tensile modulus of UHMWPE fibers individually originate from the high orientation and high crystallinity of UHMWPE chains, which gradually form in the process of hot stretch 8 . Thus, considerable efforts have been dedicated to the investigations about structural evolution of UHMWPE fibers in the hot stretch.…”