Numerical and experimental analysis of compressed composite plates with a central cutout

PRELUDIUM 13

Funding Organization: National Science Centre

Project title: Numerical and experimental analysis of compressed composite plates with a central cutout

Agreement number: UMO-2017/25/N/ST8/01066

Project implementation period: 25.01.2018 - 24.01.2022

Principal Investigator: Katarzyna Falkowicz

Project value: 174 800,00 PLN

Funds granted for Lublin University of Technology: 174 800,00 PLN

Abstract: Objective / Research Hypothesis The objective of this research project carried out in the discipline of mechanical engineering is twofold: to examine the stability and post-critical states of compressed elastic plate elements made of fibrous composites and having cut-outs with different geometry, and to investigate the effect of composite layer structures on the post-critical characteristics of elastic elements and failure load. This study concerns rectangular plates with a central cut-out of varying geometry, made of fibrous composite materials with different sequences of laminate layers. The scope of the research includes the problems of nonlinear stability and failure of composite plate structures subjected to uniform compression. The research will be conducted using a variety of research methods, combining experimental tests on real composite structures and numerical calculations by the finite element method.  The experimental studies of post-critical characteristics will be performed for the entire range of load. To assess the state of composite structures and to monitor the events occurring during the loading process the acoustic emission method will be used. Numerical calculations will enable thorough assessment of the degree of effort in individual areas of the structure. In addition, they will help determine the effect of composite layers on the post-critical characteristics of the structure. The results of the study will contribute to the development and improvement of methods for analysis and design of thin-walled composite structures with nonlinearly elastic characteristics.
The research hypothesis is that plate elements with central cut-outs made of fibrous composites can have static elastic characteristics in the post-critical state, wherein a significant impact on the formation of the plates’ elastic properties is exerted by the geometrical parameters of the cut-out and the sequence of composite layers. Research Methodology The research will involve making rectangular plates with different laminate layouts weakened by notches of irregular shapes. The elaborated physical models will be subjected to homogeneous compression with a forced flexural-torsional form of buckling that ensures stability of the structure in the post-critical state. The forced work of the structure by flexural-torsional buckling will be realized through the use of asymmetrical layouts of composite layers with specific mechanical coupling. During the study, the sample’s parameters will be measured by the electrical strain gage technique, laser sensor deflection measurement and acoustic emission technique. This will enable obtain the characteristics of the entire range of load,  along with the composite’s failure. The influence of the geometry of the cut-out in the plate on the structure’s stability as well as the elastic characteristics of the structure in the post-critical state will be examined. In addition, the impact of the laminate structures on the stability and non-linear elasticity of real structures after the loss of stability will also be examined. Discrete models will be developed to enable the analysis of buckling and nonlinear stability of the structure, including the phase of destruction. Load capacity will be determined by a composite stress failure criterion implemented in FEM, i.e. the Tsai-Wu tensor criterion. The adequacy of the developed numerical models will be verified in experimental tests. Impact of the expected results on the development of science, civilization and socjety. The project is multidisciplinary, covering the problems of composite structure mechanics and stability, as well as the mechanics of failure. The influence of the cut-out’s geometry and the composite layout on the stability, post-critical characteristics and carrying capacity of the composite plates weakened by the cut-out will be investigated, thus adding to the state of the art in this field with respect to composite thin-walled structures. The results will provide information about the development of mechanical properties of laminate structures, as well as they will help optimize the structure of the laminate such to obtain the desired nonlinear and elastic characteristics. The ability to shape the structural parameters of the tested plates with notches will allow to design the desired characteristics of the elastic element. This research will also help to enhance the skills the project’s principal investigator in the field of experimental research and numerical simulation, as well as to increase in scientific research results through publications in both domestic and international scientific journals.