Papers by Keyword: Sandwich Material

Abstract: Mine countermeasures (MCM) is a sea operation that is very risky for personnel and material losses. The development of mine technology with the discovery of modern digital mines technology currently makes mine warfare strategies change, namely by relying on the unmanned minesweeper (UMS) as a mine detector, to mitigate the impacts and risks of sea mines on naval operations. UMS vessel size is 4.8m LoA, speed 2.57m/s and beam 2.24m. The main requirements for UMS are low magnetic, low vibration, and low hydrostatic. In this study, the author will make a sandwich material made from banana fibre as an Unmanned Mine Sweeper gastric material. The choice of banana fibre is because in addition to low magnetic, its availability is very abundant in Indonesia and the price is relatively cheaper than kevlar fibre. This study uses the technique of manufacturing vacuum assessed resin infusion (VARI). Then the strength test will be carried out with a tensile test, impact test and hardness test using the ASTM standard and compared with wood and fibre materials. The test results show that abaca banana fibre is capable of being used as an unmanned minesweeper hull material.

Abstract: The current work is aimed at development of a numerical model able to describe complex damage phenomena that occur during an impact event in a sandwich structure having a honeycomb core. The complex material models employed within the research include linear-elastic and elasto-plastic material models having transverse isotropy as well as damage evolution models for both brittle failure and plastic failure. Within this paper remarks concerning the failure of the skins and core components as well as dissipated impact energy and affected regions are done.

Abstract: Sandwich construction has found extensive application in aeronautical, marine structures and container production due to high strength to weight ratio. This paper documents the compressive strength of Kevlar balsa sandwich structure with epoxy matrix subjected to edge wise compressive loads. Different modes of failure were also observed under the said loading. General modes of failure are buckling, shear crimping, dimpling and wrinkling of faces. In edge wise compression testing of Kevlar balsa sandwich, shear crimping and wrinkling of faces were the modes of failure to be observed, with each mode of failure exhibiting different compressive strength.

Abstract: In the last decade, a completely new process has been developed using the existing knowledge in machining and in flow forming and spinning processes, so called the Incremental Sheet Forming. In the process, a spherical tool, governed by CNC incrementally forms a sheet metal to form complex and asymmetric parts using minimum tooling. Several works have been published to study the process limits, optimization of paths for the forming of deep walls and to extent the formability of some alloys using temperature as a process variable. Few studies have been also published where the incremental forming of polymers has been studied. In this work, the forming of steel-polymer-steel hybrid material or Laminate Vibration Damping Steels (LVDS) is considered. Spinnability tests are used to study the process limits and the effects of having two independent sheets in the thickness of the initial blank. The maximum forming angle, forming vertical force and maximum strains near the fracture are presented for the sandwich material in comparison to steel with three different thicknesses and same composition.

Abstract: High-performance metal/polymer/metal hybrid sandwich composites are attractive materials for lightweight constructions in automotive, aerospace and naval engineering world-wide. Due to the excellent combination of mechanical, thermal and elastic properties and, as a result of high forming potential, they can be used in areas of high vibration, where high damping properties of the polymer are demanded and at the same time high strength and stiffness are given by the metal. Disadvantages can be given in case of mechanical or thermal joining of these polymer-based sandwiches because of the elastic behaviour as well as low melting temperature of the polymer. Local metal plate insertions in the soft core at the place of joining can be a solution for such kind of problems. But forming behaviour of sandwich materials with and without local inlays differs strongly. Sandwich composites of that type were produced by roll-bonding. Their quality and their position were controlled by Lockin thermography. The forming behaviour of sandwiches with different geometry, size, type and the position of the inlays was tested by deep drawing and bending and analysed with the help of digital photogrammetry and compared to experimentally obtained mechanical properties. As a result, the local inlays, as well as their geometry, size and type strongly influence the forming limit conditions. The differences in flow behaviour of non-reinforced and reinforced sandwich regions after deep drawing and bending will be presented, as well as the influence of the position of the inlays.

Abstract: Projectile impact test is carried out to investigate damage and failure behaviour under different impact velocity from 90m/s to 160m/s. Strain-time history curve on the control points are analysed in this paper. Sandwich beam dynamic response and the degree of structural degeneration under impact loading both depends on the thickness of metallic skins. The projectile impact test demonstrate difference damage characteristics between the sandwich beams with different thickness skins. The peak stress value are estimated approximately to determine the skin deformation and sandwich beam global damage degree.

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: The subproject A3 deals with the production and manufacturing and the subsequent treatment of partially strengthened, three layered, symmetrical Sandwich Structures. With this type of strengthening, complex material properties can be developed, e.g. high strength with high stiffness, good thermal joining properties at the place of strengthening, as well as an improved strength and strength absorbing ability. The forming behaviour is still widely unknown.

Abstract: This paper presents the focus of research and the structure of the Collaborative Research Centre SFB 675 “Creation of High-Strength Structures and Joints by setting up local material properties” funded in 2006 by the German Research Foundation (DFG).