Sylwester Samborski

Damage Growth in Porous Ceramics

The paper deals with the experimental method of the mechanical properties estimation at the beginning of deformation process (elastic behaviour) of the material as well as during the whole deformation stages. The idea of the method results from the observation of the loading and unloading process of the material and analysis of the strain stage.

Application of 3-D Laser Scanning Vibrometer in Determination of Free Vibration Frequencies of Composite Plates with Damage

The paper deals with experimental estimation of the frequencies of free vibrations for composite plates with damage. Two different glass-epoxy composite plates with damage were tested and their mechanical behavior was compared with their non-damaged counterparts. Dynamical properties of the tested structures were examined with the Laser Scanning Vibrometer. Finite Element Analysis (FEA) was performed simultaneously for free vibration frequencies and mode shapes. The numerical results agreed well with the experiment.

Effect of a Notch on Impact Resistance of the Epidian 57/Z1 Epoxy Material after "Thermal Shock"

Adhesive bonding is increasingly being applied as structural joining technique in highly reliable machines and appliances operating in the circumstances of variable thermomechanical loads.The manufactured specimens of the Epidian 57/Z-1 epoxy material had been subjected to cyclic thermal loading, with respect to a defined program, in a thermal shock chamber within a temperature range of ‑40°C to +60°C for 200 cycles. The accepted temperature range was typical for machinery maintenance, including the aircraft.The aim of the research was first of all determination of thermal load (fatigue), as well as the presence of notch effect on the resistance to fracture.A significant measure of the adhesive bonds quality is the repeatability of the strength examination results, both in the summary and long lasting tests. It is often more important criterion for the adhesive joint selection than higher strength of the joints using the particular adhesive.The obtained results of the conducted research have been elaborated statistically with respect to the appropriate scientific standards.

Experimental Verification of Defect’s Influence on Beams’ Dynamics Using Laser Scanning Vibrometry

This article presents paper deals with experimental verification of defect’s influence on the beam structures’ eigenfrequency extraction performed numerically with the ABAQUS Finite Element Analysis (FEA) software. The results for beams with defects were compared to those obtained for their undamaged (healthy) counterparts. The beams were made of aluminum and of a laminated glass-epoxy composite. The experiments confirmed the numerical results both quantitatively and qualitatively showing also some differences between the two materials.

Delamination Detections of Laminated, Nonlinear Vibrating and Thermally Loaded Beams

In this work, the geometrically nonlinear vibrations of fully clamped composite beams subjected to thermal changes are used to study the sensitivity of selected vibration response parameters to the presence of delamination (damage) and elevated temperature. The damage detection criterion formulated earlier for non-heated plates, based on analyzing the points in the Poincare sections of the damaged and healthy plate, is modified and tested for the case of beams additionally subjected to elevated temperatures. The importance of the actual temperature in the process of damage detection is shown.

On Parameterization of the Reinforcement Phase Distribution in Continuous Fiber-Reinforced Composites

This chapter discusses a problem of parameterization of irregular reinforcement distribution in uniaxial fiber-reinforced composites (CFRC) expressed as an area ratio of the matrix surrounding a single fiber to its perimeter. The distribution parameter, GAB, was applied in the analysis of possible relationships between the microgeometry and mechanical properties of glass-epoxy composites with random distribution of continuous fibers. Test specimens were made in a repeatable process production of the girders of helicopter blades and were tested in bending during the short beam shear tests (SBST), as well as their basic mechanical properties (e.g., the flexural modulus Ef, taking into account shear effects) were determined. The relationship between the SBST results and the theoretical topology of regular CFRC structures was presented: the square (K) and the hexagonal (H) type. The K theoretical model of fiber distribution corresponded with experimental results. It was concluded that the measure of irregular reinforcement distribution (GAB) could be used to estimate the flexural elastic modulus Ef of unidirectional CFRC composites.

A New Micromechanics Based Predictive Method for Porous Ceramics Behaviour Under Compression

A new research method of the mechanical characteristics estimation and damage assessment for porous ceramics under compression was hereby proposed. Micromechanical approach concerns initial material structure parameters before loading. Phenomenological modelling finds the relation between the stresses and the strains. SEM analysis of initial material structure and quasi-static compression of ceramic specimens with unloading and multiple reloading gives a lot of material data for modelling. A detailed analysis of material constants and damage assessment is thus possible.