Search Results (6)

Background: Disruptions in freight transportation—such as service delays, infrastructure failures, and labor strikes—pose significant challenges to the reliability and efficiency of intermodal networks. To address these challenges, this study introduces Adaptive Intermodal Transportation (AIT), a resilient and flexible planning framework that enhances Synchromodal Freight Transport (SFT) by integrating real-time disruption management. Methods: Building on recent advances, we propose two novel strategies: (1) Reassign with Delay Buffer, which enables dynamic rerouting of shipments within a user-defined delay tolerance, and (2) (De)Consolidation, which allows splitting or merging of shipments across services depending on available capacity. These strategies are incorporated into a re-planning module that complements a baseline optimization model and a continuous disruption-monitoring system. Numerical experiments conducted on a Great Lakes-based case study evaluate the performance of the proposed strategies against a benchmark approach. Results: Results show that under moderate and high-disruption conditions, the proposed strategies reduce delay and disruption-incurred costs while increasing the percentage of matched shipments. The Reassign with Delay Buffer strategy offers controlled flexibility, while (De)Consolidation improves resource utilization in constrained environments. Conclusions: Overall, the AIT framework demonstrates strong potential for improving operational resilience in intermodal freight systems by enabling adaptive, disruption-aware planning decisions. Full article

A controlled laminate consolidation is one of the most essential approaches in the production of fiber-reinforced thermoplastics components. With the use of specific consolidation models, almost the entire strength potential of the material can be exploited. However, a controlled thermo-mechanical in situ consolidation (TMIC) strategy in the fused filament fabricated (FFF) process of continuous fiber-reinforced polymer composites (CFRPC) has not been considered so far and leads to deconsolidation defects in the 3D-printed material. These defects in terms of micro and macro volumetric flaws in the joining zone indicate a poor process parameter selection and inadequate thermo-mechanical consolidation. These imperfections lead to a reduction in the fiber volume content and a significant deterioration in the mechanical properties. In this work, a self-developed test rig is presented, which is able to influence and monitor the consolidation during the additive manufacturing (AM) process with a TMIC unit in a controlled manner. To evaluate the test rig, the mechanical construction and the implemented sensors were tested for full functionality. Subsequently, test specimens were fabricated for mechanical characterization using three-point bending (3PB) tests and microstructural analysis. Based on these results, the influence of TMIC, with its dependent process parameters (consolidation force, temperature, printing speed), is presented. A perspective on the future development of controlled consolidation in AM of CFRPC is shown. Full article

In recent years, thermoplastic composites have found their place in large business sectors and are in direct rivalry to thermoset matrix composites. In order to ensure efficient and lean processes, process modeling gains ever-growing attention. This work shows the computational fluid dynamics (CFD)-modeling of a typical heating step in a thermoforming process of a thermoplastic composite sheet. When heating thermoplastic composites, the heat conduction proceeds anisotropic, and the sheets are subject to thermal deconsolidation when heated above the melting temperature of the polymer matrix adding to the anisotropic effect. These effects are neglected in known process models and this study shows the first successful attempt at introducing them into CFD-modeling of the heating of thermoplastic composite sheets. Thus, the simulation requires temperature dependent values for the anisotropic thermal conductivity and the coefficient of linear thermal expansion, which are calculated with novel physical models which were developed solely for this cause. This alters the behavior of an isotropic CFD-model and allows the successful validation via laboratory experiments using glass fiber reinforced polypropylene (PP/GF) sheets with embedded thermocouples to check the internal temperature distribution when the sheet is heated to the designated forming temperature in a composite thermoforming press. The incorporation of this newly developed process model reduces the error in the core temperature prediction from close to 70 °C to 3 °C at the forming temperature. Full article

Recent trends in the management of supply chains have witnessed an increasing implementation of the cross-docking strategy. The cross-docking strategy, being the one that can potentially improve supply chain operations, has received a lot of attention from researchers in recent years, especially over the last decade. Cross-docking involves the reception of inbound products, deconsolidation, sorting, consolidation, and shipping of the consolidated products to the end customers. The number of research efforts, aiming to study and improve the cross-docking operations, increases every year. While some studies discuss cross-docking as an integral part of a supply chain, other studies focus on the ways of making cross-docking terminals more efficient and propose different operations research techniques for various decision problems at cross-docking terminals. In order to identify the recent cross-docking trends, this study performs a state-of-the-art review with a particular focus on the truck scheduling problem at cross-docking terminals. A comprehensive evaluation of the reviewed studies is conducted, focusing on the major attributes of the cross-docking operations. These attributes include terminal shape considered, doors considered, door service mode considered, preemption, internal transportation mode used, temporary storage capacity, resource capacity, objectives considered, and solution methods adopted. Based on findings from the review of studies, some common issues are outlined and future research directions are proposed. Full article

The causes of delamination and porosities during press forming of pre-consolidated flat laminates (blanks) made of carbon fiber-reinforced poly(ether ketone ketone) (PEKK) were addressed in this study. In particular, the quality of the blank laminate was investigated before and after infrared heating. The consolidation quality was evaluated by thickness measurements, non-destructive inspection (NDI), and optical microscopy. The experimental results confirmed that deconsolidation phenomena can be related to residual stresses formed during blank forming in an autoclave, then released during infrared heating (IR) of the blank, determining most of the defects in IR heated blanks. These defects, generated at the pre-heating stage, were not fully removed in the consolidation stage of the press forming process. An annealing treatment, performed on autoclave-consolidated blanks above the glass transition temperature of the matrix, was proposed to reduce the formation of defects during IR heating. The stress relaxation phenomena during annealing were modelled using a simple viscoelastic model. Full article