Towards a process simulation tool for the laseer assisted tape placement process

A combined optical and thermal model for the laser assisted tape placement process is presented. The optical model adopts a ray tracing procedure, based on the Fresnel equations, to predict the incident heat flux on the tape and substrate near the nip-point. The heat flux distribution is subsequently used in a one-dimensional thermal model to predict the temperature distribution in the tape and substrate. The results demonstrate that for small incident laser angles a part of the laser light is reflected at the surface, which significantly influences the temperature distribution in the nip-point. The presented model allows, with a weld strength and consolidation model, optimization of the processing parameters

Experimental characterization of fibre-reinforced composites improved with nanofibres or nanotubes

A review is presented on the testing and mechanical properties of continuous fibre reinforced composites modified with nanotubes or nanofibres either dispersed in the resin or grown on the microfibres. The nano-level cross-links are shown to be able to (1) increase the fibre/matrix interfacial strength, (2) reduce the inter-fibre crack growth, and (3) improve the inter-ply delamination resistance. A positive influence on the thermal expansion is also detected. However, for unfavourable material constitutions, the strength properties can stay almost the same or even significantly deteriorate

Damage development around moulded-in holes in flat braided composites

Textile techniques like overbraiding offer the possibility to perform some function integration during the composite fabrication stage. As an example, it is possible to integrate axes or holes necessary to transfer loads to the composite structure. Moreover, this prevents drilling and therefore fracturing load-carrying fibres at a latter stage. However, this means a local reorientation of the fibre and therefore a change in properties. This paper proposes a model for the reorientation of the fibres around a moulded-in hole. A subsequent finite element analysis shows the influence of this reorientation on the stress situation around the hole. Validation on pressed glass-PPS specimens loaded under tension shows that the proposed model is able to predict damage initiation in the vicinity of the hole

L’École de l’Arena Goldoni, ou la difficile invention d’un laboratoire

De 1903 à 1914, Edward Gordon Craig multiplie les plans et les projets d’écoles : école des artisans du théâtre, école du metteur en scène, école expérimentale, école totalisatrice. Tous ces modèles tendent vers la forme du laboratoire, que l’on retrouve chez tous les grands réformateurs du théâtre au long du XXe siècle (Stanislavski, Meyerhold, Copeau, Grotowski, etc.). Ce que cherche Craig, c’est un espace de recherche fondamentale où il pourrait, entouré de collaborateurs plus que d’élèves, explorer les principes du théâtre. Au bout de ces esquisses, il y a l’ouverture éphémère de son école à l’Arena Goldoni de Florence, et surtout l’utopie d’un lieu total unifiant l’ensemble de ses intuitions depuis qu’il est parti en quête de l’artiste du Théâtre de l’avenir. Après avoir exposé l’historique de ces projets et leur réalisation partielle en 1913-1914, l’article examine quelques-unes des contradictions inhérentes à la démarche de Craig.From 1903 to 1914, Edward Gordon Craig created a flurry of plans and projects for schools: a school for theatre artisans, another for producers, an experimental school, a total school. All of these models lean towards the laboratory model, as one finds with all the great theatre reformers of the 20th Century (Stanislawksi, Meyerhold, Copeau, Grotowski, etc.) What Craig sought to establish was a space for fundamental research where he could explore the principles of theatre, surrounded more by collaborators than by students. What came of these sketches was the ephemeral opening of his school in the Goldoni Arena in Florence, but especially the realization of a utopia of a total space unifying the whole of his institutions from the beginning of his quest for the theatre artist of the future. After exposing the history of these projects and their partial realization in 1913-1914, this article will examine some of the contradictions inherent to Craig's method

Impact damage in woven fabric reinforced composites

Very often, woven fabrics are used as the reinforcement in advanced composite materials. Although the resulting inplane stiffness is lower than of their unidirectional counterparts, the excellent drapability of these materials eases the production of more general doubly curved components. In addition, the inherently low out-of-plane strength of these layered materials improves due to the undulating yarns. This paper considers both the initiation and growth of defects in these woven fabric reinforced plastics. Ten Cate Advanced Composites’ 5H Satin carbon reinforced PPS is taken as the model system. A 5H satin fabric exhibits very good drapability and PPS has a low viscosity above its melting point, enabling good yarn impregnation. Apart from this PPS has approved solvent resistance for aerospace applications and good temperature resistance. For a thermoplastic matrix, however, the material is fairly brittle

Deformability of a textile reinforcement modified with nanofibres

Deformability of a textile fabric is studied experimentally using a) friction test, b) out-of-plane compression, and c) bending. These tests reveal that a grafting of the fabric with carbon nano-fibres can significantly deteriorate its deformability. Therefore an optimal CNF mass fraction should be chosen for a particular production case, to obtain a compromise between improved strength and decreased drapability

Vibration based Structural Health Monitoring of a Composite Plate Structure with Multiple Stiffeners

A vibration based damage identification method is investigated experimentally.\ud The dynamic response of an intact and a locally damaged 16–layer unidirectional\ud carbon fibre PEKK reinforced plate structure with two stiffener sections is considered.\ud A forced–vibration set–up, including a laser vibrometer system, is employed\ud to measure the dynamic behaviour. The feasibility of the two–dimensional Modal\ud Strain Energy Damage Index algorithm to detect and localize impact induced defects\ud is demonstrated

A novel numerical mechanical model for the stress–strain distribution in superconducting cable-in-conduit conductors \ud

Besides the temperature and magnetic field, the strain and stress state of the superconducting Nb3Sn wires in multi-stage twisted cable-in-conduit conductors (CICCs), as applied in ITER or high field magnets, strongly influence their transport properties. For an accurate quantitative prediction of the performance and a proper understanding of the underlying phenomena, a detailed analysis of the strain distribution along all individual wires is required. For this, the thermal contraction of the different components and the huge electromagnetic forces imposing bending and contact deformation must be taken into account, following the complex strand pattern and mutual interaction by contacts from surrounding strands. In this paper, we describe a numerical model for a superconducting cable, which can simulate the strain and stress states of all single wires including interstrand contact force and associated deformation. The strands in the cable can be all similar (Nb3Sn/Cu) or with the inclusion of different strand materials for protection (Cu, Glidcop).\ud \ud The simulation results are essential for the analysis and conductor design optimization from cabling to final magnet operation conditions. Comparisons are presented concerning the influence of the sequential cable twist pitches and the inclusion of copper strands on the mechanical properties and thus on the eventual strain distribution in the Nb3Sn filaments when subjected to electromagnetic forces, axial force and twist moment. Recommendations are given for conductor design improvements. \ud \ud \u

Vibration Based Damage Identification in a Composite T-Beam Utilising Low Cost Integrated Actuators and Sensors

The development of integrated measurement systems for composite structures is\ud urged by the fact that a Structural Health Monitoring environment requires these systems to become an integral part of the structure. The feasibility of using low cost piezoelectric diaphragms for dynamic characterisation and vibration based damage identification in a composite T-beam structure is demonstrated. The dynamic behaviour is analysed by applying these basic electronic sound components for actuation and sensing. Impact induced damage at the skin-stiffener connection is detected and localized by applying the MSE-DI algorithm on the measured bending strain mode shapes