Carbon fibre composites offer considerable potential for mass reduction in automotive applications. However, raw material cost is one of the major factors that constraints its extensive use in this mass market. Here we report a systematic study that presents the cost contributors by considering the entire process chain of the carbon fibre manufacturing. The sensitivity analysis revealed that the final cost of Polyacrylonitrile (PAN) precursor and carbon fibres were strongly influenced by tow size. It was observed that a prompt decrease in the precursor and carbon fibre cost per kg for tow sizes from 3k to 12k, later this decrement was gradual and almost became stable above 50k. Moreover, with an increase in tow size from 3k to 50k, the contribution of the precursor on the final carbon fibre cost decreased from 76.6% to 49.6%. On the other hand, the contribution of the other factors increased with increase in the tow size, for instance, labour (9.86%-17.78%), Energy (2.49%-6.48%) and Depreciation (6.11%-11.01%). Nevertheless, precursor holds the major share in determining the final price of the carbon fibres.

The transformation of functional groups and development of radial structural heterogeneity during the thermal stabilization of polyacrylonitrile (PAN) precursor fibres were quantitatively defined for the first time using high resolution spectroscopic imaging techniques. The infrared imaging of isothermally treated fibre cross-sections reveals the radial distribution of specific functional groups (CN, CN, CH₂, CH and CO) that forms the ladder polymer structure, the most critical stage in the precursor stabilization process. Apparently, it was found that the cyclization reaction of PAN polymer chains occurred at a faster rate in the core of the fibre during heating where it further selectively promoted the dehydrogenation reaction. On the other hand, the conversion of sp³ to sp² hybridized carbon atoms was found to be higher around the skin layer compared to the core of the fibres, thus providing evidence for different cross-linking mechanisms in these regions. The simultaneous occurrence of a higher extent of cyclization and dehydrogenation reactions due to the excess heat developed in the core and a delay of oxygen diffusion in to the core of the fibres played a critical role in the polymer chain cross-linking in the skin and core regions that further led to the evolution of radial heterogeneity in the fibres. It was also found that the mechanical properties were built upon the structural transformations and the variation in the modulus across the fibre cross-section further confirmed the reaction mechanism.

Process parameters, especially in the thermal stabilization of polyacrylonitrile (PAN) fibers, play a critical role in controlling the cost and properties of the resultant carbon fibers. This study aimed to efficiently handle the energy expense areas during carbon fiber manufacturing without reducing the quality of carbon fibers. We introduced a new parameter (recirculation fan frequency) in the stabilization stage and studied its influence on the evolution of the structure and properties of fibers. Initially, the progress of the cyclization reaction in the fiber cross-sections with respect to fan frequencies (35, 45, and 60 Hz) during stabilization was analyzed using the Australian Synchrotron-high resolution infrared imaging technique. A parabolic trend in the evolution of cyclic structures was observed in the fiber cross-sections during the initial stages of stabilization; however, it was transformed to a uniform trend at the end of stabilization for all fan frequencies. Simultaneously, the microstructure and property variations at each stage of manufacturing were assessed. We identified nominal structural variations with respect to fan frequencies in the intermediate stages of thermal stabilization, which were reduced during the carbonization process. No statistically significant variations were observed between the tensile properties of fibers. These observations suggested that, when using a lower fan frequency (35 Hz), it was possible to manufacture carbon fibers with a similar performance to those produced using a higher fan frequency (60 Hz). As a result, this study provided an opportunity to reduce the energy consumption during carbon fiber manufacturing.

This study investigates the influence of printing parameters on the tensile properties and void architecture of poly(lactic) acid (PLA) parts fabricated using the fused filament fabrication (FFF) technique. Two Taguchi optimisation methods were employed to identify the optimal parameter combinations for maximising tensile performance. The results revealed a positive correlation between tensile performance and nozzle diameter (ND). Notably, the analysis of the coefficient of variance (COV) studies revealed that both tensile strength and modulus exhibited minimal variation within a tight range of 5.5%, suggesting a high degree of process consistency in achieving desired mechanical properties regardless of the chosen parameters within the investigated range. Micro-computed tomography (micro-CT) analysis was used to quantify void characteristics within the as-printed samples. Micro-CT analysis confirmed the influence of ND and layer thickness (LT) on void architecture. By establishing structure–property relationships, the study revealed that larger NDs paired with finer LTs yielded superior tensile properties due to reduced void content. This work highlights the interplay between printing parameters, void architecture, and the resulting mechanical behaviour of MEX-based PLA parts.

Material Extrusion Additive Manufacturing (MEAM) has witnessed significant research interest since 2009. The optimization of printing and material parameters to enhance the mechanical properties of 3D-printed parts has been the primary research objective. Among commonly used polymers, Polylactic Acid (PLA) has emerged as a preferred material due to its ease of use, biodegradability, and relatively high mechanical strength. While the incorporation of discontinuous fiber reinforcements (dFR) into PLA filaments offers the potential for improved tensile performance, existing literature suggests that their impact is often negligible or even detrimental. Furthermore, the optimization of printing parameters for MEAM-dFR composites has not been extensively studied as for pristine polymers. This review aims to investigate the influence of printing parameters on the tensile performance of various PLA-based dFRCs. Three fiber types—basalt, carbon, and wood—were selected to analyse their effects on tensile properties. A bubble chart was developed to visualize the correlations between raster angle, fiber content, layer thickness, printing speed, and extrusion temperature on the composite tensile properties. The findings highlight the importance of material selection in enhancing tensile performance. Additionally, the need for more comprehensive statistical studies on the optimization of printing parameters for MEAM-dFRCs is emphasized.