Monika Ostapiuk

Interface analysis of fiber metal laminates

Fiber metal laminates (FMLs) are the hybrid laminates consisting of alternating thin layers of metal sheets and fiber-reinforced composite material. Interface between metal and polymer layer plays a significant role. FMLs have both low density and high relative strength, and other good properties as high damage tolerance: fatigue and impact characteristics, corrosion, and fire resistance. In present work, the microstructure of the aluminum-epoxy/glass and aluminum-epoxy/carbon composites is characterized. The interface between metal and polymer composites with surface treatment and without surface treatment at different pressures was examined. It was observed that pretreatment of the aluminum has a significant effect on the zone between metal and polymer composite. In the interface, there is a direct contact between anodizing layer and resin without fibers, the same for epoxy/glass and epoxy/carbon laminates. The low pressure in autoclave process has a detrimental effect on the structure. It is responsible for the formation of the porosity and delamination in polymer layer and interface between aluminum and polymer composites. Untreated surface of aluminum sheet is characterized by too low adhesion to epoxy composite, especially with carbon reinforcement.

The impact behavior of aluminum hybrid laminates

Purpose – The purpose of this study was to carry out the analysis of impact resistance for aluminum hybrid laminates and polymer matrix composites reinforced with glass and carbon fibers. Damage modes and damages process under varied impact energies are also presented and discussed. Design/methodology/approach – The subject of examination were fiber metal laminates – FMLs (Al/CFRP and Al/GFRP). The samples were subjected to low-velocity impact by using a drop-weight impact tester. The specimens after impact were examined using non-destructive and destructive inspection techniques. Findings – The hybrid laminates are characterized by higher resistance to impact in comparison to the conventional laminates. The delaminations between composite layers as well as the delaminations on metal/composite interface and lateral cracks are the prevailing type of destruction mechanisms. No significant relationships between metal volume friction coefficient vs response to the impact were recorded for the hybrid laminates...

NUMERICAL FEM ANALYSIS FOR THE PART OF COMPOSITE HELICOPTER ROTOR BLADE

Composites are a group of materials applied more extensively in aviation constructions. Their good physicalchemical and mechanical properties, and particularly from the ratio of strength to low density give a dominant place for applying in thin- walled constructions as a load carrying-capacity structure. One of the most effort parts of the helicopter is the thin-walled structure of rotor blade. The numerical calculations are a very helpful tool for solutions and analysis of materials. In this paper was presented the preliminary analysis of the effort of composite materials. Then it was possible to identify the region where is the high risk of failure in load- carrying capacity structure. The numerical tool applied to the analysis was the ABAQUS/Standard program. The estimation of the level of effort in the composite materials in the performed studies were the maximum stress criterion, the Tsai-Hill criterion, the tensor Tsai-Wu criterion and the Azzi-Tsai-Hill criterion. The mechanical properties required for analysis were performed in the way of experiments way, according to the standard specifications for this type of materials. FEM analysis was shown the effort elements of the construction, where were the highest level of tension stresses.

Experimental investigation on the influence of fibers orientation on the failure of carbon hybrid laminates

Purpose – The purpose of this paper is to present microstructural and fractographic analysis of damage in aluminum (2024T3)/carbon-fiber reinforced laminates (AlC) after static tensile test. The influence of fiber orientation on the failure was studied and discussed. Design/methodology/approach – The subject of examination was AlC. The fiber–metal laminates (FMLs) were manufactured by stacking alternating layers of 2024-T3 aluminum alloy (0.3 mm per sheets) and carbon/epoxy composites made of unidirectional prepreg tape HexPly system (Hexcel, USA) in [0], [± 45] and [0/90]S configuration. The fractographic analysis was carried out after static tensile test on the damage area of the specimens. The mechanical tests have been performed in accordance to ASTM D3039. The microstructural and fractographic analysis of FMLs were studied using optical (Nikon SMZ1500, Japan) and scanning electron microscope (Zeiss Ultra Plus, Germany). Findings – FMLs based on aluminum and carbon/epoxy composite are characterized by...

Qualitative analysis of the margins of restorations made with different filling resins

Purpose: In this study the comparative results obtained from examinations of two different restorative composites with different cavities filling method are presented. Micro‐CT was used for the evaluation of the marginal integrity and quality of composite fillings in connection with microstructural investigations made by both optical and scanning electron microscopy.

Interrelationships Between Morphometric, Densitometric, and Mechanical Properties of Teeth in 5-Month-Old Polish Merino Sheep

Interrelationships between morphological, densitometric, and mechanical properties of deciduous mandibular teeth (incisors, canine, second premolar) were investigated. To perform morphometric, densitometric, and mechanical analyses, teeth were obtained from 5-month-old sheep. Measurements of mean volumetric tooth mineral density and total tooth volume were performed using quantitative computed tomography. Microcomputed tomography was used to measure total enamel volume, volumetric enamel mineral density, total dentin volume, and volumetric dentin mineral density. Maximum elastic strength and ultimate force of teeth were determined using 3-point bending and compression tests. Pearson correlation coefficients were determined between all investigated variables. Mutual dependence was observed between morphological and mechanical properties of the investigated teeth. The highest number of positive correlations of the investigated parameters was stated in first incisor indicating its superior predictive value of tooth quality and masticatory organ function in sheep. Positive correlations of the volumetric dentin mineral density in second premolar with final body weight may indicate predictive value of this parameter in relation with growth rate in sheep. Evaluation of deciduous tooth properties may prove helpful for breeding selection and further reproduction of sheep possessing favorable traits of teeth and better masticatory organ function, leading to improved performance and economic efficiency of the flock.

Analysis of the bending and failure of fiber metal laminates based on glass and carbon fibers

Abstract The purpose of this paper is to investigate the mechanisms of cracking and failure in fiber metal laminates (FMLs) subjected to 3-point bending. Two types of laminates, based on the glass/epoxy and carbon/epoxy composites, were selected for the study. The paper presents the failures of matrix and fibers as well as the effects of different thicknesses of metal layers on the tested laminates. The mechanisms of failure observed for the two tested types of fibers with uniform thickness of aluminum sheets seem similar. The results demonstrate that the tested laminates exhibit the following failure modes: fiber breakage, matrix cracking, fiber/matrix debonding, delamination, and anodic layer failure. Given the behavior of aluminum under the compressive and tensile stresses, the aluminum layer acts as a barrier preventing FML failure during bending. In addition to aluminum layer thickness, the fiber type and composite layer directions are also important factors to be considered.