Papers by Keyword: Hybrid Structure

Abstract: The further development of in-mold-assembly (IMA) technologies for structural hybrid components is of great importance for increasing the economic efficiency and thus the application potential. This paper presents an innovative IMA process concept for the manufacturing of bending loaded hybrid components consisting of two outer metal belts and an inner core structure made of glass mat reinforced thermoplastic (GMT). In this process, the core structure, which is provided with stiffening ribs and functional elements, is formed and joined to two metal belts in one single step. For experimental validation of the concept, the development of a prototypic molding tool and the manufacturing of hybrid beams including process parameters are described. Three-point bending tests and optical measurement technologies are used to characterize the failure behavior and mechanical properties of the produced hybrid beams. It was found that the innovative IMA process enables the manufacturing of hybrid components with high energy absorption and low weight in one step. The mass-specific energy absorption is increased by 693 % compared to pure GMT beams.

Abstract: In this study the experimental and theoretical optical analysis of a hybrid microcavity (HM) based in porous silicon (PS) and nanoporous anodic alumina (NAA) are presented. The microcavity was centered in the visible region at 760 nm. Distributed Bragg reflector (DBR) was obtained using galvanostatic anodizing method and while NAA by the two-step anodization technique. From SEM micrographs the HM different regions are observed. HM optical characterization in the visible region was done, considering two different light sources, point and non-point respectively. These results reveal a decrease in the quality factor (Q) from 350 to 190 when the source is exchanged; this behavior has been mainly attributed to the light scattering at NAA. Furthermore, it was possible to study Q change, through transmittance simulation using the transfer matrix and Landau-Lifshitz-Looyenga theoretical methods. When a point light source is used, there are no optical losses making possible to sense 1% of analyte resulting in a 0.29 nm redshift of the resonant peak. According with these results we propose to apply the HM as chemical optic sensor.

Abstract: In this work, core-shell ZnO@SiO₂ nanoparticles (NPs) were infiltrated into a macro/meso-porous silicon (PS) structure, to study its luminescent properties. The core-shell ZnO@SiO₂ NPs were obtained by colloidal synthesis. The core-shell ZnO@SiO₂ NP was 5 nm in diameter. The macro/meso-PS structure was made in two steps: we obtained the macroporous silicon (macro-PS) layer fist and the mesoporous silicon (meso-PS) layer second. This process was conducted using different electrolyte solutions, and the change of electrolyte led to a decrease in the special charge region over the wall macro-PS layer; this allowed the building of the meso-PS layers on the walls and the bottom of the macro-PS layer. The SEM results show the cross-section of the macro/meso-PS structure with and without core-shell ZnO@SiO₂ NPs. These SEM images show that the core-shell ZnO@SiO₂ NPs that infiltrated into macro/meso-PS structure were more efficiently bonded over all the porous walls. The core-shell ZnO@SiO₂ PL interacted with the macro/meso-PS structure, modifying its PL intensity and controlling a shift toward a lower wavelength.

Abstract: The shelter for archaeological areas aims to protect ruins from damages, in order to preserve their historical values, while the excavation work represents a destructive action. The shelter design process for archaeological areas includes dealing with some contradictions, due to the multiplicity of constraints and the complexity of the application contexts. The article aims to state the appropriate use of membranes and temporary structures in these fragile environments through a new concept of textile lightweight solution coming from a decision support matrix. In this applicative example, the elasticity of the proposed textile material – that is a polyurethane-coated knitted textile – and its combination with a bending-active structural element, become a key aspect for reconfiguring the whole system to different sets of problems. The example therefore understands active bending as an approach to generating new structural forms, in which common load bearing behavior is found due to the structures inherently large elasticity and inner stress state.

Abstract: The effects of CNR diameter and CNR number on tensile properties of the CNR-graphene hybrid structure (CGHS) were studied by molecular dynamics simulation in this paper. Results show that interactions between adjacent graphene sheets are significantly strengthened by the cross-linked CNRs. For CGHSs, the maximum strength is ~64.0 GPa and the maximum Young’s modulus strength is ~763 GPa. When the diameter of CNRs is large or the CNR linkers are dense, the tensile strength of CGHSs reached the maximum and the fracture mechanism of CGHSs changed from CNR-graphene junction fracture to graphene sheet fracture. Present work should serve as guide to experiments concerning physical properties of this novel material.

Abstract: Innovative lightweight structures realized by employing assembly injection molding bears high potential. Using assembly injection molding, complex shaped hybrid structures can be manufactured in a precise and fast processing step. Though, especially the interface quality of a hybrid joint is a crucial factor, which determines the overall quality of such lightweight structures. High bonding strength values were achieved between aluminum and multiple polymeric materials with double-lap joints manufactured by employing assembly injection molding. Thereby, the influence of aluminum surface pre-treatments as well as intrinsic adhesion modifications of the polymeric materials were investigated.

Abstract: Multi-material-design offers high potential for weight saving and optimization of engineering structures but inherits challenges as well, especially robust joining methods and long-term properties of hybrid structures. The application of joining techniques like ultrasonic welding allows a very efficient design of multi-material-components to enable further use of material specific advantages and are superior concerning mechanical properties.The Institute of Materials Science and Engineering of the University of Kaiserslautern (WKK) has a long-time experience on ultrasonic welding of dissimilar materials, for example different kinds of CFRP, light metals, steels or even glasses and ceramics. The mechanical properties are mostly optimized by using ideal process parameters, determined through statistical test planning methods.This gained knowledge is now to be transferred to application in aviation industry in cooperation with CTC GmbH and Airbus Operations GmbH. Therefore aircraft-related materials are joined by ultrasonic welding. The applied process parameters are recorded and analyzed in detail to be interlinked with the resulting mechanical properties of the hybrid joints. Aircraft derived multi-material demonstrators will be designed, manufactured and characterized with respect to their monotonic and fatigue properties as well as their resistance to aging.

Abstract: The main objective for an economic and ecological use of raw materials is the achievement of closed raw material cycles. Because of that, not only the manufacturing procedures are important during the development of new materials but also the recycling processes. Within the increased use of lightweight construction in recent years, the application of multi-material or hybrid structures reach high significance for the automotive industry. In this development, especially the carbon fibre reinforced plastics (CFRP) gained its importance. However, currently there are no recycling strategies available for hybrid structures; complete recycling processes for CFRP are still expandable. This work presents methods for separation of hybrid structures made of metal and CFRP, as well as the corresponding process windows and the boundary conditions. The separation is performed by introduction of thermal heat and the behaviour of these bonded compounds is analyzed based on shear tensile tests. The results of these studies are used to develop a complete recycling process for reclamation of hybrid structures.

Abstract: . In technical applications components are often exposed to vibrations with a broad range of frequencies. To ensure structural integrity and a convenient usage for the customer, materials with good damping characteristics are desirable. Especially stiff and lightweight structures tend to be prone to vibrations. Fibre metal laminates (FML) offer great potential for lightweight design applications due to their good fatigue behavior. By using carbon fiber reinforced plastics (CFRP) as part of the laminates very good strength and stiffness to weight ratios can be obtained. To improve the damping characteristics of this hybrid material an additional layer of elastomer can be added between the CFRP and the metal, generating a fiber-metal-elastomer laminate (FMEL). In this present study the damping behavior of different layups of FMEL was examined. Two different metal sheets and two types of elastomer were used, also the layup of the constituents was variated. Vibrations were induced with a frequency range from 100 Hz to 20 kHz by mounting the laminates onto a speaker. The vibration response was measured with a piezoelectric accelerometer. Eventually the different laminate layups were compared with each other to determine the influence of the individual constituents regarding the damping characteristics. The different elastomer types and prepreg layups affected the damping of vibrations, whereas the use of different metal sheet materials showed only little influence.

Abstract: In this study hybrid structure were produced by direct metal laser sintering of maraging steel (MS1) powder onto the surface of commercial mold steels. The over-sintering method should be analyzed to find the optimum pre-and post-heat treatment to minimize the internal stresses. The internal stress is directly proportional to the deformation if the solid thick part is reduced to thin plate like parts. Based on this recognition the deformation of the plates over-sintered with MS1 could be analyzed in order to explore the internal stresses and the effect of different pre-and post-heat treatments were examined.