Abstract: In recent years fibre reinforced plastics play a constantly improving role in a growing field of applications. From the chemical industry through sports equipments up to aircraft production - composites can be used in all these industrial areas. Although materials like glass fibre reinforced or carbon fibre reinforced plastics have a lot of applications in structural parts the knowledge about dimensioning and processing techniques is not exploited for the design of composite structures. If the parts and structures are not built for high performance applications such as in aircrafts, often principles and theories based on metal design are used to design the parts.
In this article the basics of structural mechanics for composite materials are presented. An overview about how to work with anisotropic material in design as well as in processing is given and the most important CAE tools for composite design are shortly presented.
Abstract: Most composite components are constructed in a very safe way, with thick walls and many laminate layers. The potential of lightweight construction will not be fully tapped. In a typical computation of the behavior of a component, the wall thickness and fiber directions have to be entered into the simulation system. The result is the load-dependent deformation of the component. That approach takes a lot of time to get an optimized construction. A better way for optimizing fiber-reinforced composites is the use of simulation algorithms to get an optimal material distribution. In this case, the simulation output shows the optimal layer thickness and fiber directions for every node depending on the selected maximum deformations and the load of the structure. This method was used to reduce the weight of the special, extremely energy-saving vehicle called “Sax 3” of the student project “fortis saxonia” for the Shell Eco-marathon 2008. Thus it has become possible to keep the weight of the chassis of the vehicle under 10 kg. This shows the high potential of the implementation of this optimization approach for fiber-reinforced composites.
Abstract: A current research effort at the Polymer Engineering Center (PEC) consists on providing the tools required to understand and predict defects that arise during the molding of fiber reinforced composites. This review starts with a comprehensive research summary in the field of computer simulation of composites molding and then presents our current work regarding computer simulations of flexible fiber suspensions
Abstract: Experimental results of performance of non-crimp fabric composites are presented in this paper. In order to characterize in-plane shear properties of these composites, tensile and compression tests of [±452]S specimens were carried out. Two directions of loading are considered: warp (Shear warP: SP) and weft (Shear wefT: ST). This corresponds to laminates with the following lay-up: SP = [+45/-45/+45/-45]S; ST = [-45/+45/-45/+45]S. Although both types of laminates are cut from the same plate, mechanical performance in tension is rather different: laminate cut in weft direction exhibit higher shear modulus, shear strength and shear strain at failure than samples cut in warp direction. Fractography showed that different behavior of the materials is caused by much earlier damage initiation and accumulation in SP laminates. Analysis of images obtained from optical microscopy indicated that premature failure is most likely caused by stitches that prevent free rotation of bundles (shear deformation).
Abstract: This review aims at reporting on very recent developments in the synthesis, properties and (future) applications of rubber nanocomposites. Nanocomposites are the materials for the future, which have improved mechanical properties. Reinforcement is especially important for the application of elastomeric materials because the mechanical strength of unfilled elastomers is generally poor. Commonly isometric fillers like carbon black or fumed silica are used for reinforcing elastomers.Rubber nanocomposites play an important role in engineering, construction and aerospace applications. This new family of materials exhibit enhanced properties at very low filler level, usually ≤ 5 wt %. Rubber nanocomposites exhibit very good Young’s modulus , storage modulus, thermal stability , gas barrier properties and flame retardancy.
Abstract: Conventional mechanical and structural properties allow to describe the complete composite material. They do, however, not describe the reaction during the pyrolysis process. The dynamic mechanical thermal analysis (DMTA) is a technique which is used to characterize materials. In particular, the DMTA method is used to observe the viscoelastic nature of polymers. Another interesting application area of the DMTA is the simulation of pyrolysis experiments to obtain carbon/carbon composites (C/C composites). The pyrolysis process of carbon-fibre-reinforced plastics (CFRP) was performed by means of inert gas (Ar, ambient pressure) under a defined time-temperature profile or alternatively approached by short time sweeps in a DMTA. So the temperature dependence of the elastic modulus (E-modulus) and of the internal damping (tan δ) are determined starting from the cured carbon-fibre-reinforced plastic to the transformed C/C composites. The analyses were applied for different matrix resins. The shown method improves the access to usually hidden mechanical and structural properties and requires further investigation of the entire polymerization and pyrolysis processes.
Abstract: This review aims at reporting on very recent developments in the, properties and applications of Green Composites. One very important aspect of green composites is that they can be designed and tailored to meet different requirements. Recent advances in natural fiber development offer significant oppurtunities for improved materials from renewable resources. Biocomposites offer a significant non-food market for crop-derived fibres and resins. Considerable growth has been seen in the use of biocomposites in the automotive and decking markets over the past decade or so, but application in other sectors has hitherto been limited. Recent developments of different biodegradable polymers and biocomposites are discussed in this review article.
Abstract: The application of natural fibres as polymer reinforcement is of extreme interest, especially in combination with biodegradable polymers. Such “green” composite represent a step forward to eco-design and environmentally friendly applications. The use of biodegradable polylactic acid (PLA) on the basis of renewable resources in addition to the biodegradable polyvinyl alcohol (PVA) on petrochemical basis is compared in this study with the application of polypropylene (PP) as a surrounding matrix for sisal fibres. According to the law of similarities, the chemically similar structure of natural fibres and PVA and PLA provides stronger fibre-matrix bonding characteristics compared to PP. This was experimentally validated applying single-fibre pull-out tests, where the effect of improved bonding is further investigated in terms of tensile and impact composite behaviour. SEM investigation was further applied to describe failure modes of natural fibre composites.
Abstract: This paper gives a wide view over recent research in dynamic characteristics and
vibration damping properties of fiber-reinforced, polymer-matrix composites, with emphasis on
parameters governing damping, such as fiber volume fraction, fiber orientation, exciting frequency,
aspect ratio and fiber-matrix interface, as well as stacking sequence for laminated composites. Both
experimental and analytical models are discussed and parameters used to measure the amount of
vibration damping are covered. Natural-fiber based composites are handled in detail in the last
section of this paper.