Papers by Keyword: Experimental Mechanics

Abstract: Glass and carbon fibre composites and hybrid glass/carbon composites are materials often used in wind turbine blades. In Africa wind turbines have to operate in warm climates. The present study presents the results of an experimental study on the mechanical properties of these composites at elevated temperatures. For this purpose, the composite specimens are fabricated by hand lay-up process to investigate their static and dynamic properties at high temperatures. The properties studied include Inter-laminar Shear Stress (ILSS), Dynamic Mechanical Properties (DMA) such as storage modulus, loss modulus and loss factor using ASTM standards. The inter-laminar shear failure strength of carbon fibre and hybrid glass-carbon fibre composites are found to be close whereas the glass transition and damping behavior of the hybrid composites are higher making them suitable for wind turbine blades operating at high temperatures. Short Beam Shear (SBS) test data are evaluated using chi-square goodness of fit statistical tests and the correlation coefficients from linear regression analysis are determined. Normal, lognormal and 2-parameter Weibull statistical distributions are used at 5% significant level.

Abstract: Innovative development and production trends particularly in automotive and aerospace industries significantly influence also design of opening panels assemblies (doors, windows, stiffened panels etc.). New trends show that metal constructions of these modules will be gradually replaced by new material conceptions leading to hybrid plastic material-composite-metal constructions. This fact is logically reflected by methods and methodologies in testing, used both in pre-development, prototype and finally even in batch phase of the development and production. The main topic of the paper deals with presentation of several testing devices and used measurement methods for testing of qualitative parameters of rigidity and strength of both the whole module groups and their fundamental reinforcing components made of composite materials.

Abstract: The work described involves the implementation of a testing bench prototype, used to control the behavior of heart valves, taking into account the characteristics of the blood.

Abstract: This paper describes investigations of magnetorheological elastomers subjected to cyclic loading. The procedure comprised over 1 million of loading cycles per specimen. Mechanical properties of the manufactured composites have a tendency to stabilize in time. This leads to the conclusion that these MRE have a high application potential in the areas which are connected with energy dissipation, such as damping of vibrations.

Abstract: The emergence recently of a thermoelastic stress analysis (TSA) capability exploiting low-cost, compact and rugged microbolometer detector technology provides a significant opportunity topromote a broader use of this powerful non-contact full-field stress analysis technique. An area whereit has considerable and hitherto unexplored potential is in in-situ structural health monitoring (SHM).The present paper outlines the case for a nexus between SHMand TSA in this new form. It is proposedthat the approach should yield diagnostic and prognostic capabilities surpassing those of some existingSHM modalities. An F/A-18 centre-fuselage full-scale structural fatigue test is employed as a casestudy to illustrate the practical feasibility of the approach and to underscore some of its potential.Although the case study focuses on an aircraft structure, the concept has potential application to awide variety of different engineering assets across the aerospace, civil and maritime sectors.

Abstract: In this paper, the fracture process of WCp/Cu functionally graded materials(FGMs) was investigated. The used materials were fabricated by powder metallurgy using tungsten carbide(WC) particles and copper(Cu) matrix, and had functionally graded layers. In order to investigate the fracture process of the FGM, three-point-bending tests of rectangular specimens were carried out. From the results, it can be seen that the bending performance of FGM structures with increasing WC content from head layer to the bottom layer excels that of FGM structures with decreasing WC content in three-point-bending tests.

Abstract: Thin film processing has been a driving technology in microelectronics and mechanics for years. The reliability of such devices is often limited by the failure of thin films. Therefore a deeper understanding of fatigue mechanisms of thin films through experiments is necessary to develop physical based lifetime models. Thus, this paper focuses on a novel setup for micro beam bending of thin metal films on Si cantilever substrate and first results will be presented.

Abstract: The environment is a prominent issue today. Designing environmentally sustainable products is an attempt to address this question. In many cases, natural materials are environmentally friendly for product design manufacturing. The goal of this work is to study the mechanical behaviour of NL10 and NL30 cork agglomerates. Compression, shear and bending tests in sandwich specimens made of glass or jute fiber in facings and cork agglomerates as core were carried out. The sandwich specimens were manufactured by Resin Transfer Moulding (RTM) process. Results show that NL30 has a higher compression strength and shear resistance than NL10 agglomerate due to its manufacturing process, which originates superior density, but the NL30 agglomerate superior density is undesirable. Sandwich test specimens that presented failure by rupture of the core in both types of tests, core shear tests and three point bending tests, showed that the failure is mainly adhesive occurring between the adhesively joined cork grains. Since grains are unaffected and remain intact, it is possible to improve these materials by using better agglutinants and new bonding techniques with the intent of getting cork agglomerates with higher shear and flexural strength.

Abstract: In this work the methodology of determining mechanical and magnetomechanical properties (mainly magnetostriction) of original composite material on epoxy resin matrix and powdered Giant Magnetostrictive Material (Terfenol-D) has been presented. Researches were carried out in order to differentiate properties of the GMM composite with two different volume fraction of Terfenol-D powder (35% and 45%) in comparison with bulk Terfenol-D. Results show that composites magnetostriction highly depends on volume fraction of Terfenol-D powder, and it is few times lower than in monolithic material. Moreover a possible ways of application were indicated.

Abstract: The two-dimensional deformation of wood with different grains under shearing loads was measured using an electronic speckle pattern interferometry (ESPI) technique. The radical, tangential and end sections of Douglas firs (Pseudotsuga menziesii) were used as specimens. Results revealed that the deformation values significantly vary for every part of the specimens, and the ring directions of earlywood and latewood, which compose the annual rings, have an effect on the two-dimensional deformation of wood.