Influence of processing on the fiber length degradation in fiber reinforced plastic parts

Abstract

Fiber reinforced plastics are gaining importance for their weight saving potential due to the influence of sociopolitical topics such as energy efficiency and conservation of resources. Long fibers and short fibers are increasingly used for structural components. The high requirements on the performance in automotive, aerospace and also the sports and leisure sector demand a full exploitation of these materials´ potential. For optimization a precise understanding of the processing effects is inevitable. In this work two different testing parts were produced in a single-stage direct processing on an injection molding compounder and tested for their respective resulting fiber properties. Hardly any significant influence of the process parameters on the mechanical properties was found. However, increasing fiber length at the end of the cavity could be observed as well as an influence of increasing fiber concentration on a significantly lowered fiber length. The latter can be assigned to higher fiber-fiber interaction. An influence of a change in wall thickness on the fiber length reduction could only be determined for low fiber contents. For higher fiber contents the fiber length degradation is dominated by fiber-fiber interaction.

Calibration of Fiber Orientation Simulations for LFT—A New Approach

“…The properties of the fiber microstructure (orientation, length, and concentration), especially in the case of discontinuously reinforced plastics such as SFT or LFT, can usually only be influenced to a very limited extent by its constituent properties and compound constitution (initial fiber orientation, initial fiber length and initial fiber concentration). However, these properties are rather a result of the processing [13,26,[33][34][35][36][37]. One of the most widely used processing methods is injection molding, in which even complex parts can be produced in large quantities [32,37].…”

“…Due to the interaction of the fibers, the fiber orientation depends on the fiber length and concentration [5], which also applies to interchanged dependencies. The fiber length depends on the fiber orientation and concentration while the distribution of fibers depends inversely on the fiber orientation and length [36]. Due to wall adhesion and mold cooling, high shear rates are present in the skin or shear layers, and lower shear rates are found in the core layer in the middle of the cavity.…”

“…Because fiber length is significantly reduced within the plastification unit, and this is not part of the simulation, the number averaged fiber length (see Table 1) was experimentally measured as described in [36] at the sprue and specified as a boundary condition in the respective process simulations. As expected, the results show that, with an increasing fiber content, the probability of fiber-fiber interaction increases significantly, and fiber breakage occur more frequently.…”

“…In order to investigate the influence of the different versions of the iARD fiber orientation model as explained in Section 1.1.8 on the resulting fiber orientation distribution the following software versions of Moldex3D ® with the different fiber orientation model versions Because fiber length is significantly reduced within the plastification unit, and this is not part of the simulation, the number averaged fiber length (see Table 1) was experimentally measured as described in [36] at the sprue and specified as a boundary condition in the respective process simulations. As expected, the results show that, with an increasing fiber content, the probability of fiber-fiber interaction increases significantly, and fiber breakage occur more frequently.…”

�Green Carbon� from Algae for Automotive Applications

“…The efficiency of fibre reinforcement increases as interruptions between fibres, in the plastic mass, become increasingly rare [6]. Between the complexity of the achievable components and their mechanical properties there is a correlation depending on the fibre length [7,8]. The most commonly used reinforcements are flax, hemp as well as jute, kenaf, sisal or abaka reinforcements [6].…”