Peter Wierach

Bio: Peter Wierach is an academic researcher from German Aerospace Center. The author has contributed to research in topics: Carbon nanotube & Structural health monitoring. The author has an hindex of 13, co-authored 102 publications receiving 618 citations.

Multifunctional Composites for Future Energy Storage in Aerospace Structures

Abstract: Multifunctionalization of fiber-reinforced composites, especially by adding energy storage capabilities, is a promising approach to realize lightweight structural energy storages for future transport vehicles Compared to conventional energy storage systems, energy density can be increased by reducing parasitic masses of non-energy-storing components and by benefitting from the composite meso- and microarchitectures In this paper, the most relevant existing approaches towards multifunctional energy storages are reviewed and subdivided into five groups by distinguishing their degree of integration and their scale of multifunctionalization By introducing a modified range equation for battery-powered electric aircrafts, possible range extensions enabled by multifunctionalization are estimated Furthermore, general and aerospace specific potentials of multifunctional energy storages are discussed Representing an intermediate degree of structural integration, experimental results for a multifunctional energy-storing glass fiber-reinforced composite based on the ceramic electrolyte Li14Al04Ti16(PO4)3 are presented Cyclic voltammetry tests are used to characterize the double-layer behavior combined with galvanostatic charge–discharge measurements for capacitance calculation The capacitance is observed to be unchanged after 1500 charge–discharge cycles revealing a promising potential for future applications Furthermore, the mechanical properties are assessed by means of four-point bending and tensile tests Additionally, the influence of mechanical loads on the electrical properties is also investigated, demonstrating the storage stability of the composites

Lamb-Wave based Structural Health Monitoring in Polymer Composites

Abstract: Deutsche Forschungsgemeinschaft: "Integrierte Bauteiluberwachung in Faserverbunden durch Analyse von Lambwellen nach deren gezielter Anregung durch piezokeramische Flachenaktoren"

Improved electrical conductivity of NCF-reinforced CFRP for higher damage resistance to lightning strike

Abstract: Silver-coated knitting yarns are used in an NCF to increase the electrical conductivity of CFRP-laminates A test textile containing section-wise four different knitting yarns has been produced The threads differ in yarn count and degree of silver-coating Depending on the yarn’s linear resistance, the conductivity in thickness direction increases by up to two orders of magnitude to >100 S/m The in-plane conductivity is significantly higher as well Combining conductive knitting yarns with conductive toughening interleaves further increases the electrical conductivity Lightning strike resistance benefits from the conductivity improvement The damage decreases particularly in the lower fibre layers, eg at a depth of 10 mm by app 90% In spite of the higher laminate conductivity, additional conductive interleaves do not further improve lightning strike resistance The damage is smaller than in the reference, but larger than in a comparative laminate where only the knitting yarn is conductive

Overview of the common dlr/onera project "active twist blade" (atb)

Abstract: Individual blade control (IBC) as well as higher harmonic control (HHC) for helicopter rotors promises to be a method to increase flight performance and to reduce vibration and noise. For those controls, an additional twist actuation of the blade is needed. Within the DLR/ONERA partnership, a project called “Active Twist Blade” (ATB) was established on a Joint Team in which two concepts for active twist blades are investigated. This paper presents an overview of the project as well as a description of the two concepts including first demonstrators to prove the feasibility of those activation mechanism.

Flexural Mechanical Properties of Hybrid Epoxy Composites Reinforced with Nonwoven Made of Flax Fibres and Recycled Carbon Fibres

Abstract: Can a hybrid composite made of recycled carbon fibres and natural fibres improve the flexural mechanical properties of epoxy composites compared to pure natural fibre reinforced polymers (NFRP)? Growing environmental concerns have led to an increased interest in the application of bio-based materials such as natural fibres in composites. Despite their good specific properties based on their low fibre density, the application of NFRP in load bearing applications such as aviation secondary structures is still limited. Low strength NFRP, compared to composites such as carbon fibre reinforced polymers (CFRP), have significant drawbacks. At the same time, the constantly growing demand for CFRP in aviation and other transport sectors inevitably leads to an increasing amount of waste from manufacturing processes and end-of-life products. Recovering valuable carbon fibres by means of recycling and their corresponding re-application is an important task. However, such recycled carbon fibres (rCF) are usually available in a deteriorated (downcycled) form compared to virgin carbon fibres (vCF), which is limiting their use for high performance applications. Therefore, in this study the combination of natural fibres and rCF in a hybrid composite was assessed for the effect on flexural mechanical properties. Monolithic laminates made of hybrid nonwoven containing flax fibres and recycled carbon fibres were manufactured with a fibre volume fraction of 30% and compared to references with pure flax and rCF reinforcement. Three-point bending tests show a potential increase in flexural mechanical properties by combining rCF and flax fibre in a hybrid nonwoven.

Carbon nanotubes for biomedical applications

Abstract: Carbon nanotubes (CNTs) have many unique physical, mechanical, and electronic properties. These distinct properties may be exploited such that they can be used for numerous applications ranging from sensors and actuators to composites. As a result, in a very short duration, CNTs appear to have drawn the attention of both the industry and the academia. However, there are certain challenges that need proper attention before the CNT-based devices can be realized on a large scale in the commercial market. In this paper, we report the use of CNTs for biomedical applications. The paper describes the distinct physical, electronic, and mechanical properties of nanotubes. The basics of synthesis and purification of CNTs are also reviewed. The challenges associated with CNTs, which remain to be fully addressed for their maximum utilization for biomedical applications, are discussed.

Additively manufactured carbon fiber-reinforced composites: State of the art and perspective

Abstract: While polymer additive manufacturing (AM) has advanced significantly over the past few decades, the limitations in material properties, speed of manufacture, and part size have relegated this technology to the space of rapid prototyping rather than the legitimate manufacture of end-use parts. Carbon fiber offers a low density, a low coefficient of thermal expansion, and high thermal conductivity and is an ideal material for bringing polymer-based AM from the realm of form and fit to that of form, fit, and function. Use of carbon fiber in AM can improve material properties, reduce the time required to manufacture functional parts compared with traditional subtractive technologies, and reduce warping, thereby enabling a larger possible build envelope. Therefore, the addition of carbon fiber to various AM technologies is of increasing interest in academic and industrial communities. This paper examines the work performed in this fast-growing area to date. Specifically, the effects of fiber reinforcement on the structure and mechanical properties of 3D printed parts are investigated within the body of literature. Upper bounds for tensile properties of carbon fiber composites are theoretically evaluated and compared with experimentally measured values. Moreover, current and potential applications of additively manufactured carbon fiber composites in the context of desktop 3D printing and big area AM are discussed. Recent innovations and industry breakthroughs in this field are also examined. This review is intended to organize and synthesize the present body of work surrounding AM of carbon fiber reinforced plastics, identify the most promising technologies, and prescribe viable research and development paths forward to advance AM from the application space of rapid prototyping to that of functional, load-bearing, end-use parts.

A review of modelling and analysis of morphing wings

Abstract: Morphing wings have a large potential to improve the overall aircraft performances, in a way like natural flyers do. By adapting or optimising dynamically the shape to various flight conditions, there are yet many unexplored opportunities beyond current proof-of-concept demonstrations. This review discusses the most prominent examples of morphing concepts with applications to two and three-dimensional wing models. Methods and tools commonly deployed for the design and analysis of these concepts are discussed, ranging from structural to aerodynamic analyses, and from control to optimisation aspects. Throughout the review process, it became apparent that the adoption of morphing concepts for routine use on aerial vehicles is still scarce, and some reasons holding back their integration for industrial use are given. Finally, promising concepts for future use are identified.

Functionalized composite structures for new generation airframes: a review

Abstract: The uncontroversial superiority of functionalized composite structures for new generation airframes has been well acknowledged by the research community. Such an approach has the potential to substantially enhance system performance and reduce overall manufacture–operation–maintenance expenditure. Recent progress in informatics and high-capability computing devices has offered a brand-new springboard for the aerospace community to reshuffle its traditional R&D criteria for functionalized composite structures. Particularly, artificial intelligence (AI), an intriguing information processing technique, exhibits outstanding effectiveness in accommodating the highly demanding requirements of new generation airframes. Appropriate utilization of AI techniques in functionalized composite airframe design will contribute to the realization of high-capability intelligent systems. The applications of advanced composite structures, artificial intelligence and sensing network techniques in aircraft industry are briefly reviewed in this paper, in correlation with various novel concepts. As a specific case study, an AI technique-based composite structure with the capability of structural health monitoring was developed. An artificial neural network was customized and trained using digitized spectrographic characteristics extracted from a multi-point sensing network. The system was then validated by executing on-line health diagnostics, and the results indicate excellent performance of AI techniques in functionalized composite structures.

Multifunctionality in Epoxy Resins

Abstract: Epoxy resin will continue to be in the forefront of many thermoset applications due to its versatile properties. However, with advancement in manufacturing, changing societal outlook for the chemic...