Andrzej Czulak

Bio: Andrzej Czulak is an academic researcher from Dresden University of Technology. The author has contributed to research in topics: Composite number & Ultimate tensile strength. The author has an hindex of 11, co-authored 43 publications receiving 402 citations.

Optimisation of the rivet joints of the CFRP composite material and aluminium alloy

Abstract: Purpose: The project included analysis of strain, cracking, and failure of riveted joints of plate elements made from the carbon-fibre-reinforced plastics (CFRP) and from the 6061 aluminium alloy. Design/methodology/approach: The modelled static tensile strength test carried out for the plates from CFRP and from the 6061 aluminium alloy joined with the steel rivet. Computer simulation was carried out with IDEAS software package employing the FEM. Findings: Simulations using the mesh with a bigger number of FEM elements do not yield better accuracy of calculations and do not improve convergence with the results of laboratory experiments. Only the calculation time gets longer. Computer simulation has also show that the type of contacts employed between elements affects the results significantly. Research limitations/implications: For the composite materials, joints between materials and computer simulation examinations are planed. Practical implications: Results obtained for the mesh with 4 and 5 FEM elements are the closest to the results of laboratory experiments, which is confirmed by the strain plot. Simulations using the mesh with a bigger number of FEM elements do not yield better accuracy of calculations and do not improve convergence with the results of laboratory experiments. Only the calculation time gets longer. Computer simulation has show that the type of contacts employed between elements affects the results significantly. Originality/value: The paper presents influence of fibre mesh closeness on convergence of the results with laboratory tests. Simulation results were collected and compared with the laboratory static tensile strength tests results.

Modification of glass reinforced epoxy composites by ammonium polyphosphate (APP) and melamine polyphosphate (PNA) during the resin powder molding process

Abstract: The aim of the studies was to manufacture glass reinforced epoxy composites using technology based on hot pressing with improve flame resistance with good mechanical properties. Ammonium polyphosphate (APP) and melamine polyphosphate (PNA) were used as flame retardants with ranging from 5 to 20 wt %. The thermal and mechanical properties of the composites were determined in the course of TGA analysis, flammability UL-94 test, limiting oxygen index (LOI) technique, Fourier Transform Infrared Spectroscopy, ultrasonic test and static tensile test. The flame retardancy of modified composites was significantly improved with addition of ammonium polyphosphate and melamine polyphosphate. Moreover, in most cases addition of flame retardants increased strength of composites. This study confirmed that fast and highly efficient Resin Powder Molding manufacturing process allows to produce high quality composites.

Novel MRE/CFRP sandwich structures for adaptive vibration control

Abstract: The aim of this work was the development of sandwich structures formed by embedding magnetorheological elastomers (MRE) between constrained layers of carbon fibre–reinforced plastic (CFRP) laminates. The MREs were obtained by mechanical stirring of a reactive mixture of substrates with carbonyl-iron particles, followed by orienting the particles into chains under an external magnetic field. Samples with particle volume fractions of 11.5% and 33% were examined. The CFRP/MRE sandwich structures were obtained by compressing MREs samples between two CFRP laminates composed. The used A.S.SET resin was in powder form and the curing process was carried out during pressing with MRE. The microstructure of the manufactured sandwich beams was inspected using SEM. Moreover, the rheological and damping properties of the examined materials with and without a magnetic field were experimentally investigated. In addition, the free vibration responses of the adaptive three-layered MR beams were studied at different fixed magnetic field levels. The free vibration tests revealed that an applied non-homogeneous magnetic field causes a shift in natural frequency values and a reduction in the vibration amplitudes of the CFRP/MRE adaptive beams. The reduction in vibration amplitude was attributed mainly to the stiffening effect of the MRE core and only a minor contribution was made by the enhanced damping capacity, which was evidenced by the variation in damping ratio values.

Thermal conductivity of polymers and polymer nanocomposites

Abstract: Polymers are widely used in industry and in our daily life because of their diverse functionality, light weight, low cost and excellent chemical stability. However, on some applications such as heat exchangers and electronic packaging, the low thermal conductivity of polymers is one of the major technological barriers. Enhancing the thermal conductivity of polymers is important for these applications and has become a very active research topic over the past two decades. In this review article, we aim to: 1). systematically summarize the molecular level understanding on the thermal transport mechanisms in polymers in terms of polymer morphology, chain structure and inter-chain coupling; 2). highlight the rationales in the recent efforts in enhancing the thermal conductivity of nanostructured polymers and polymer nanocomposites. Finally, we outline the main advances, challenges and outlooks for highly thermal-conductive polymer and polymer nanocomposites.

Carbon fiber reinforced metal matrix composites: Fabrication processes and properties

Abstract: This paper reviews the research and development works conducted over the past few decades on carbon fiber reinforced metal matrix composites (CFR-MMC). The structure and composition of carbon fiber and its bonding to metal matrix have an impact on the properties of the resulting CFR-MMC remarkably. The research efforts on process optimization and utilizing of carbon fibers are discussed in this review. The effect of carbon fiber on structural, physical and mechanical properties of metal matrix composite are studied as well. This review also provide an overview of the research to date on various fabrication methods that is used for production of CFR-MMC.

Buckling-induced smart applications: recent advances and trends

Abstract: A paradigm shift has emerged over the last decade pointing to an exciting research area dealing with the harnessing of elastic structural instabilities for ‘smart’ purposes in a variety of venues. Among the different types of unstable responses, buckling is a phenomenon that has been known for centuries, and yet it is generally avoided through special design modifications. Increasing interest in the design of smart devices and mechanical systems has identified buckling and postbuckling response as a favorable behavior. The objective of this topical review is to showcase the recent advances in buckling-induced smart applications and to explain why buckling responses have certain advantages and are especially suitable for these particular applications. Interesting prototypes in terms of structural forms and material uses associated with these applications are summarized. Finally, this review identifies potential research avenues and emerging trends for using buckling and other elastic instabilities for future innovations.