Composites science and technology

Voids, the most studied type of manufacturing defects, form very often in processing of fiber-reinforced composites. Due to their considerable influence on physical and thermomechanical properties ...

https://journals.sagepub.com/doi/pdf/10.1177/0021998318772152

Voids in fiber-reinforced polymer composites: A review on their formation, characteristics, and effects on mechanical performance:

Reference EPFL-ARTICLE-184271doi:10.1016/j.compositesa.2012.08.001View record in Web of Science Record created on 2013-02-27, modified on 2017-05-10

Composites Part A: Applied Science and Manufacturing

This paper investigates comprehensive knowledge regarding joining CFRP and aluminium alloys in available literature in terms of available methods, bonding processing and mechanism and properties. The methods employed comprise the use of adhesive, self-piercing rivet, bolt, clinching and welding to join only CFRP and aluminium alloys. The non-thermal joining methods received great attention though the welding process has high potential in joining these materials. Except adhesive bonding and welding, other joining methods require the penetration of metallic pins through joining parts and therefore, surface preparation is unimportant. No model is found to predict the properties of jointed structures, which makes it difficult to select one over another in applications. The choice of bonding methods depends primarily on the specific applications. The load-bearing mechanism of bolted joints is predominantly the friction that is the first stage resistance. Hybrid joints performance is enhanced by combining rivets, clinch or bolts with adhesives.

/pdf/joining-of-carbon-fibre-reinforced-polymer-cfrp-composites-b1dn74dni2.pdf

Joining of carbon fibre reinforced polymer (CFRP) composites and aluminium alloys-A review

Bistable plates for morphing structures: A refined analytical approach with high-order polynomials

Active composite structures based on thermoplastic matrix systems are highly suited to applications in lightweight structures ready for series production. The integration of additional functional components such as material-embedded piezoceramic actuators and sensors and an electronic network facilitates the targeted control and manipulation of structural behaviour. The current delay in the widespread application of such adaptive structures is primarily attributable to a lack of appropriate manufacturing technologies. It is against this backdrop that this paper contributes to the development of a novel manufacturing process chain characterized by robustness and efficiency and based on hot-pressing techniques tailored to specific materials and actuators. Special consideration is given to detailed process chain modelling and analysis focusing on interactions between technical and technological aspects. The development of a continuous process chain by means of the analysis of parameter influences is described. In conclusion, the use of parameter manipulation to successfully realize a unique manufacturing line designed for the high-volume production of adaptive thermoplastic composite structures is demonstrated.

/pdf/process-chain-modelling-and-analysis-for-the-high-volume-5b1bmmw5tx.pdf

Process Chain Modelling and Analysis for the High-Volume Production of Thermoplastic Composites with Embedded Piezoceramic Modules

Anisotropic characterization of magnetorheological materials

In contrast to common joining technologies for composite-metal hybrid structures such as bonding and riveting, contour joints offer promising potential in terms of manufacturing efficiency and mechanical performance For composite structures, joining systems with positive locking elements enable to pass high loads and are capable to achieve high degrees of material utilisation To enhance the performance of hybrids, a multi-scale structuring approach is sought Aiming at high rate production, especially in automotive industry, an intrinsic manufacturing approach whereat the composite part is joined to the metallic part during its consolidation process has been developed This paper demonstrates the intrinsic manufacturing principles of continuous fibre-reinforced thermoplastic hollow profiles with multi-scale-structured load introduction and mainly focuses on the development of a fibre appropriate design Based on a design of experiment approach, numerical parameter studies for the optimisation of macro contour have been carried out to create a general design guideline

Design of multi-scale-structured Al-CF/PA6 contour joints

In lightweight design, clinching is a cost-efficient solution as the joint is created through localized cold-forming of the joining parts. A clinch point’s quality is usually assessed using ex-situ destructive testing methods. These, however, are unable to detect phenomena immediately during the joining process. For instance, elastic deformations reverse and cracks close after unloading. In-situ methods such as the force-displacement evaluation are used to control a clinching process, though deviations in the clinch point geometry cannot be derived with this method. To overcome these limitations, the clinching process can be investigated using in-situ computed tomography (in-situ CT). However, a clinching tool made of steel would cause strong artefacts and a high attenuation in the CT measurement, reducing the significance of this method. Additionally, when joining parts of the same material, the sheet-sheet interface is hardly detectable. This work aims at identifying, firstly, tool materials that allow artefact-reduced CT measurements during clinching, and, secondly, radiopaque materials that can be applied between the joining parts to enhance the detectability of the sheet-sheet interface. Therefore, both CT-suitable tool materials and radiopaque materials are selected and experimentally investigated. In the clinching process, two aluminium sheets with radiopaque material in between are clinched in a single-step (rotationally symmetric joint without cut section). It is shown that e.g. silicon nitride is suited as tool material and a tin layer is suitable to enhance the detectability of the sheet-sheet interface.

/pdf/clinching-in-in-situ-ct-experimental-study-on-suitable-tool-3ikhfp1zf5.pdf

Clinching in In-situ CT – Experimental Study on Suitable Tool Materials

Novel 3D-textile reinforced composites with a stretched fibre orientation have very good specific mechanical properties and outstanding energy absorption capabilities. Additionally, advanced textile techniques and the combination of different fibre materials enable even the efficient manufacture of hybrid 3D-textile performs with tailored property profiles. Dependent on the application, 3D-textile performs can be adjusted to specific requirements regarding stiffness, strength and crash-worthiness. Thus, hybrid 3D-textile preforms with tailored property profiles are excellent candidates for the application in impact and crash components of modern lightweight structures. For the load-adapted design of highly dynamically loaded lightweight structures and especially for the tailoring of adequate textile reinforcement structures, a validated knowledge about the strain rate dependent mechanical material behaviour of 3D-textile reinforced composites and appropriate material and failure models are necessary. This article focuses on the qualitative and quantitative investigation of the strain rate dependent material properties of composites with hybrid multi-layered flat bed weft knitted fibre reinforcements consisting of different fibre combinations such as glass-glass, glass-aramid and glass-polyethylene.

Maik Gude

Papers

Process Chain Modelling and Analysis for the High-Volume Production of Thermoplastic Composites with Embedded Piezoceramic Modules

Anisotropic characterization of magnetorheological materials

Design of multi-scale-structured Al-CF/PA6 contour joints

Clinching in In-situ CT – Experimental Study on Suitable Tool Materials

Tailored 3D-textile reinforced composites with load-adapted property profiles for crash and impact applications