Introduction

The aerospace industry is aiming for a cleaner means of transport. One way to achieve this is by making transportation lighter, thus directly improving fuel efficiency and reducing environmental impact. A further aim, of the industry, is to reduce maintenance time to lessen operating costs, which can result in a reduction of air transport costs, benefitting both passenger and freight services. Current developments to support these aims include using advanced materials, with the current generation of aerospace structures being 50% composite materials. These materials offer a weight reduction whilst maintaining adequate stiffness; however, their damage mechanics are very complex and less deterministic than those of metals. This results in an overall reduced benefit. Structures are manufactured thicker using additional material to accommodate unknown or unpredictable failure modes, which cannot be easily detected during maintenance. A way to overcome these issues is the adoption of a structural health monitoring (SHM) inspection system. Structural health monitoring (SHM) is understood to be the continuous or periodic and automated method for determining and monitoring the condition of a monitored object within condition monitoring (according to DIN ISO 17359). This is conducted through measurements with permanently installed or integrated transducers and the analysis of the measurement data. Its purpose is to detect damage, for example, cracks or deformations, at an early stage to initiate countermeasures. [...

Selecting feasible trajectories for robot-based X-ray tomography by varying focus-detector-distance in space restricted environments

Computed tomography has evolved as an essential tool for non-destructive testing within the automotive industry. The application of robot-based computed tomography enables high-resolution CT inspections of components exceeding the dimensions accommodated by conventional systems. However, large-scale components, e.g. vehicle bodies, often exhibit trajectory-limiting elements. The utilization of conventional trajectories with constant Focus-Detector-Distances can lead to anisotropy in image data due to the inaccessibility of some angular directions. In this work, we introduce two approaches that are able to select suitable acquisitions point sets in scans of challenging to access regions through the integration of projections with varying Focus-Detector-Distances. The variable distances of the X-ray hardware enable the capability to navigate around collision structures, thus facilitating the scanning of absent angular directions. The initial approach incorporates collision-free viewpoints along a spherical trajectory, preserving the field of view by maintaining a constant ratio between the Focus-Object-Distance and the Object-Detector-Distance, while discreetly extending the Focus-Detector-Distance. The second methodology represents a more straightforward approach, enabling the scanning of angular sectors that were previously inaccessible on the conventional circular trajectory by circumventing the X-ray source around these collision elements. Both the qualitative and quantitative evaluations, contrasting classical trajectories characterized by constant Focus-Detector-Distances with the proposed techniques employing variable Focus-Detector-Distances, indicate that the developed methods improve the object structure interpretability for scans of limited accessibility

Development of intimate contact during processing of carbon fiber reinforced Polyamide-6 tapes

Contact development between the surfaces of two tapes is considered as a critical step in processing carbon fiber reinforced thermoplastic composites. In this study, the development of intimate contact between carbon fiber reinforced Polyamide-6 (PA-6) tapes is investigated experimentally using consolidation experiments and X-ray computed tomography for quantitative contact characterization. The experimental results indicate that the development of intimate contact occurs in the range of seconds even when temperatures are only slightly above the melting temperature and applied pressures is in the range of 1-4 kPa. Experimental data are compared with the results of the two analytical models proposed by Lee and Springer as well as Yang and Pitchumani. Both models overestimate the time needed to reach full contact for the PA-6 tape. In comparison to previously investigated PEEK materials, PA-6 has a relatively low viscosity and the tapes possess a resin-rich layer near the surface, which seems to influence the contact development process. Besides the assumptions made for viscosity, the sensitivity to input parameters describing the surface topology strongly influence the model results and the accuracy of predictions. </jats:p