Taking into Account Glass Fiber Reinforcement in Polymer Materials: The Nonlinear Description of Anisotropic Materials 2011-26-0057

Fibre-Reinforced Plastic (FRP) are composite materials made of a polymer matrix reinforced with fibres. The fibres are usually fibreglass, carbon or aramid, while the polymer is usually an epoxy, vinylester or polyester thermosetting plastic. FRP are commonly used in the aerospace, automotive, marine, and construction industries. Especially in the automotive industry, the replacement of metal parts with substitutes made from FRP plays a major role. Applications include parts in direct contact to the engine like oil pans, intake manifolds and cylinder head-covers. It is also used in fixings of covering parts like the dashboard in the interior, bumpers and fenders in the exterior. The components manufactured using FRP materials usually undergo injection molding process where the matrix materials are reinforced with different fiber contents to enhance the strength of the material. The complexity of FRP materials not only lies with the manufacturing process, but also in the engineering use of these materials in Finite Element Analysis (FEA).

Simulation engineers have traditionally used FEA to predict the structural performance of FRP materials. However, the technique presumes uniform distribution of fiber throughout the molded part. Generally, mold filling parameters and part geometry variations greatly affect the fiber distribution and orientation and, therefore, the part's resulting mechanical and thermal performance. Typically, analysts use a safety factor to compensate for the gap in knowledge of how material properties vary in a FRP part. However, the safety factor neglects the part's fiber orientation-induced anisotropy, accounting instead for its effect by degrading to some degree the strength and modulus values determined by tensile testing. Unfortunately, this approximation overestimates properties in some areas and underestimates them in others. One has to consider fiber orientation-induced anisotropy, mold filling parameters, to avoid this approximation. This is achieved by linking a process simulation with structural analysis, a process called integrative simulation. In the above mentioned applications, the components are all potentially loaded with high dynamic forces in case of pressure impulses, rock slide or accidents. Therefore a verification of their crashworthiness is necessary. The combination of high-speed deformation and anisotropic material behavior demands an integrative approach for crash simulation. So the better material properties come along with a more complex simulation and part design process.

All necessary description for composites in Finite Element (FE) simulations can be defined within DIGIMAT, from nonlinear materials over strain rate dependency to failure. On that base, the results of integrative simulation show convincingly better results for an impact through an injection molded plate than with the conservative traditional simulation.