Siebert Geralt

Dr. Siebert Geralt

Institute for Structural Engineering, Department of Civil Engineering and Environmental Sciences, Universität der Bundeswehr München, Werner-Heisenberg-Weg 39, 85579 Neubiberg, Munich, Germany

Research Focus & Metrics

Academic Career Length

21Years (2006-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

View All Publications
30 December 2022 in Polymers
Verified
Journal Article
Open access
PDF file
HMHossein Mohammadi
Hossein Mohammadi
ZAZaini Ahmad
Zaini Ahmad
SMSaiful Amri Mazlan
Saiful Amri Mazlan
MJMohd aidy faizal Johari
Mohd aidy faizal Johari
Siebert GeraltSiebert Geralt
Siebert Geralt
Seyed Saeid Rahimian KoloorSeyed Saeid Rahimian Koloor
Seyed Saeid Rahimian Koloor
The enhancement of fuel economy and the emission of greenhouse gases are the key growing challenges around the globe that drive automobile manufacturers to produce lightweight vehicles. Additionally, the reduction in the weight of the vehicle could contribute to its recyclability and performance (for example crashworthiness and impact resistance). One of the strategies is to develop high-performance lightweight materials by the replacement of conventional materials such as steel and cast iron with lightweight materials. The lightweight composite which is commonly referred to as fiber-reinforced plastics (FRP) composite is one of the lightweight materials to achieve fuel efficiency and the reduction of CO2 emission. However, the damage of FRP composite under impact loading is one of the critical factors which affects its structural application. The bumper beam plays a key role in bearing sudden impact during a collision. Polymer composite materials have been abundantly used in a variety of applications such as transportation industries. The main thrust of the present paper deals with the use of high-strength glass fibers as the reinforcing member in the polymer composite to develop a car bumper beam. The mechanical performance and manufacturing techniques are discussed. Based on the literature studies, glass fiber-reinforced composite (GRP) provides more promise in the automotive industry compared to conventional materials such as car bumper beams.

20 March 2023 in Glass Structures & Engineering
Verified
Journal Article
Open access
PDF file
Markus FeldmannMarkus Feldmann
Markus Feldmann
MLMaximilian Laurs
Maximilian Laurs
JBJan Belis
Jan Belis
NBNebojsa Buljan
Nebojsa Buljan
ACAnnie Criaud
Annie Criaud
ASAnna Sikynova
Anna Sikynova
Since the beginning of 2021, CEN/TS 19100 Design of Glass Structures has been available in its first three parts. The fourth part is expected soon. This Technical Specification of the European standards organisation CEN is as a pre-standard of a corresponding future Eurocode. These documents constitute the first ever comprehensive design code for the entire structural glass engineering field on the European market for the first time. In addition to a clear outline, the Technical Specification has been drafted to be compatible with EN 1990 “Basis of Design” and to address glass-specific design matters, particularly related to robustness and redundancy. Although the standard still has the status of a CEN/TS, thereby allowing the European nations the option of whether to introduce it, either in full or in parts, it already contains national openings through which the European countries can adapt the design results to their own safety level by National Determined Parameters (NDPs). Such an approach already anticipates the future Eurocode, which is expected to be published as EN 19100—Design of Glass Structures. This article provides some context on the history and concept behind the new documents and gives an overview of the design rules and the corresponding technical background of the different parts of CEN/TS 19100.

19 January 2023 in Polymers
Verified
Journal Article
Open access
PDF file
SKSafdar ali khan
Safdar ali khan
Seyed Saeid Rahimian KoloorSeyed Saeid Rahimian Koloor
Seyed Saeid Rahimian Koloor
KWKing Jye Wong
King Jye Wong
Siebert GeraltSiebert Geralt
Siebert Geralt
Mohd Nasir TAMINMohd Nasir TAMIN
Mohd Nasir TAMIN
In fiber-reinforced polymer (FRP) composite laminate structures operating under fluctuating stresses, interface delamination is seen as one of the significant damage mechanisms. The constant degradation of their relatively low interlaminar strength and stiffness are the primary reasons for delamination. This study develops an interlaminar fatigue damage model to quantify the mechanics of the damage process and address the reliability of composite structures. The model considers the failure process in two stages: (1) damage due to degradation of interlaminar elastic properties, and (2) damage due to dissipation of fracture energy through the damage evolution process. The model is examined for a case study of mode I fatigue loading of a carbon-fiber-reinforced polymer (CFRP) composite laminate. The results show that the interlaminar normal stress is confined to the crack front region, with tensile stress peaks at 70% of the interlaminar strength. Furthermore, a stable interface crack growth is predicted initially, followed by a sudden crack “jump” at 14,000 cycles. The simulation results are compared with the experimental data, with very good agreement, showing a successful validation of the fatigue model.

8 August 2024 in Glass Structures & Engineering
Verified
Journal Article
Open access
PDF file
LELena Efferz
Lena Efferz
CSChristian Schuler
Christian Schuler
Siebert GeraltSiebert Geralt
Siebert Geralt
The mechanical and safety-relevant properties of tempered architectural glass are tested using destructive bending strength and fracture pattern tests. The edge stress provides essential information on the quality of the tempering process and can, therefore, be used to ensure quality characteristics. The paper shows that the current valid evaluation method for edge stress, according to ASTM C 1279-09, is unsuitable for architectural glass. The chamfer which is required for tempered glass by the European standards for tempered glass prevents the direct measurement of retardation and edge stress. Therefore, an extrapolation of the retardation curve towards the edge is necessary. The paper compares fitting functions of different polynomial degrees to determine and assess the edge stress. The objective is to develop a proper evaluation method of edge stress for quality control in the latest inline measurement systems which can be applied to replace operator-dependent measuring devices. The study presents appropriate methods and evaluates them through experimental investigations using the phase shift technique and multiple wavelength photoelasticity.

22 October 2018 in ce/papers
Verified
Journal Article
Closed access
PDF file
GNGordon Nehring
Gordon Nehring
Siebert GeraltSiebert Geralt
Siebert Geralt

1 June 2024 in Glass Structures & Engineering
Verified
Journal Article
Open access
PDF file
LELena Efferz
Lena Efferz
KTKerstin Thiele
Kerstin Thiele
MSMiriam Schuster
Miriam Schuster
CSChristian Schuler
Christian Schuler
Siebert GeraltSiebert Geralt
Siebert Geralt
JSJens Schneider
Jens Schneider
Thermally toughened safety glass must meet safety requirements in the building industry. Here, destructive tests are defined in the product standards, which must be carried out on small, standardized format (360 mm × 1100 mm) glass elements to determine the fracture pattern and bending strength. This is costly and not in the interests of sustainability. As part of the quality control of optical anisotropy effects in thermally toughened glass, isochromatic scans that can provide information on the edge stress are acquired. The evaluation of the isochromatics and retardations at the edge with deduction of the edge stress and transfer to bending strength and fracture pattern could provide essential findings for assuring the safety requirements of thermally toughened glass. In this experimental investigation, the surface and edge stress were measured on standardized format thermally toughened safety glass, with different edge processing and glass thicknesses from three different suppliers. Afterwards, the fracture pattern is controlled, or the bending strength is analyzed in a destructive four-point bending test. Conclusively, the results from the photoelastic and destructive tests are compared to determine whether the photoelastic measurement methods used to measure surface and edge stress can be employed as quality control.