Papers by Keyword: Charpy Test

Abstract: Hybrid Fibre Metal Laminates (HFMLs) are composite materials made of alternating layers of metal and fibre-reinforced polymers. The paper discusses the development of HFMLs and their applicability in aerospace applications when compared to conventional FMLs. Experimental (Mechanical and vibrational) studies are conducted to assess the strength and vibrational properties of these materials. Mechanical and vibrational characteristics of the proposed materials are explored and presented. Aluminium 2024 T3 sheets as metal layer and hybrid (glass, carbon) polymer fibre reinforcements are used for developing hybrid lightweight laminates. SEM (scanning electron microscope), and stereomicroscopy are used for microscopic characterization studies and a universal testing machine (UTM) is employed to perform mechanical characterization. The impact behaviour of these materials is also disclosed using the Charpy impact test. An improvement in the strength and vibrational properties are clearly observed in the FMLs after fibre hybridization, which may be due to improved bonding compatibility in carbon prepregs. The outcome of the research contributes to the advancement of lightweight materials for next-generation aerospace structures.

Abstract: The hereby paper presents comparison of numerically modelled Charpy test in LS-Dyna environment with an experiment on accredited Charpy impact test machine. The comparison was applied to dimensions of a strained sample at selected points and energy consumed for the sample fracture and strains during the test.

Abstract: High-speed tensile tests were carried out to investigate strain rate effect on both yield stress and failure strain using ASTM D1822 Type-S specimens made of polycarbonate. Based on test results, parameters for a material model suitable for polymers are determined, and numerical analysis is carried out to simulate test results. The material model is used to simulate tensile test using a dog-bone specimen and Charpy test other than the tensile test of Type-S specimens. It is found that good predictions can be obtained when rate dependent material parameters are used. Further, the high-speed tensile test considered in the present study is suitable for selection of parameters for material modeling of polymers for impact analysis.

Abstract: Because of high stiffness, high strength and low density, etc., polymeric composite materials are widely used in high technology area, such as aeronautic and aerospace engineering where impact is one of the most common loadings. In this paper, impact energy absorption properties of a carbon fiber reinforced plastic (CFRP) plate, which was made through vacuum assisted resin transfer molding (VARTM) process, were tested though Charpy impact tests with single-edge notched specimens. In the experiments, the effects of impact directions and notch length on the energy absorption property were considered. The results show different impact directions lead to different Charpy impact strength and different fracture modes. When the angle between the fiber and the impact direction is large, fiber break mode dominates the break, exhibiting higher Charpy impact strength. When the impact direction-fiber angle is small, delamination is the main fracture mode, showing lower Charpy impact strength. Depending on different fracture modes, the enhancement of the resin due to a post curing process has totally opposite effects on the Charpy impact strength. For the delamination mode, the enhancement of resin increases the Charpy impact strength of the CFRP specimen. However, for the fiber break mode, it decreases the impact strength. This phenomenon can be attributed to the effect of voids. The impact strength calculated from the typical formula is also affected by the initial notch length significantly, because the fracture surface in this experiment is no longer a plane.

Abstract: The buriti (Muritia flexuosa) fiber are among the lignocellulosic fibers with apotential to be used as reinforcement of polymer composites. In recent years, the buriti fiber has been characterized for its properties as an engineering natural material. The toughness of buriti composites remains to be a evaluated. Therefore, the present work evaluated the toughness of epoxy composites reinforced with different amounts of buriti fibers by means of Charpy impact tests. It was found a significant increase in the impact resistance with the volume fraction of buriti fibers. Fracture observations by scanning electron microscopy revealed the mechanism responsible for this toughness behavior.

Abstract: This research paper deals with an investigation of the influence of honeycomb core compression on the mechanical properties of sandwich structures. These structures consist of prepreg facing layers and two different material types of honeycomb and are produced by modified compression molding called Crush-Core technology. Produced structures are mechanically tested in three-point bending test and subjected to low-velocity impact and Charpy impact test.

Abstract: The possible use of tungsten alloys as structural materials in future fusion reactor divertors strongly depend on their ductile-to-brittle transition temperature (DBTT). The present paper gives an overview on different rod and plate materials fabricated by PLANSEE. It is demonstrated that DBTT is clearly improved compared to commercially available standard materials. Moreover, the significant impact of the microstructure on fracture mode and on toughness is discussed in detail.

Abstract: The article focuses on the technical measurements which could be applied to the fracture surfaces of the steel Charpy specimens in order to apply the Fractal Analysis. One could calculate the fractal dimension not directly for a fracture, but for a profile of the fracture. Most common methods for generation of fracture profile are cross-cut techniques and profile measurements techniques [1-2]. We apply three principal methods: Profilometer, Interferometer Light Microscope and the Vertical Section for a specimen made of XC65 after the Charpy test. We compare the advantages and the limits for each technique. We use the Box Counting algorithm applied in the Image J program for determining the fractal dimension of the fracture surface in all three experimental techniques. Then we could characterize the roughness of the fracture profile at different magnifying power by the estimated fractal dimension.

Abstract: Many components from industry are subjected to repeated impacts, or in some cases these impacts can appear as additional loads. Repeated impacts define a fatigue phenomenon known under the name of Impact Fatigue. Because the strain rate changes the material characteristics it is to expect that the material properties at impact fatigue to be different in regard to those obtained at non-impact fatigue. First studies at repeated impacts were made at the middle of 19th Century, but the progress in this field is not as fast as non-impact fatigue, due to experimental difficulties and the lake of standards for impact fatigue tests. This paper presents a classification of repeated impact tests, and starting from this a series of parameters used for durability estimation will be analyzed. The high number of parameters used by different authors creates difficulties in comparison the different laboratories results. The importance of the shape and dimensions of specimens, and the stiffness of bearing are highlighted. In order to avoid these influences the authors proposed an experimental technique, based on testing of Charpy specimens, in similar conditions as single impact test. The paper presents a series of results obtained for additional impacts overlapped to a cyclic load.