The influence of variability and defects on the mechanical performance of tailorable composites

Aligned hybrid-fibre discontinuous composites offer the ability to tailor their mechanical response through careful microstructural design. However, with tailorability comes microstructural complexity, which in turn leads to many sources of variability and defects. A virtual testing framework was further extended to investigate the influence of variability and defects on the mechanical performance of various aligned discontinuous composite material systems. This approach identified the most critical sources of variability as (i) fibre strength, (ii) the distance between fibre ends, or (iii) the level of fibre-type intermingling, depending on the material system. Fibre vacancy defects were shown to have the most significant influence on the strength and ductility of aligned discontinuous composites, although this sensitivity can be reduced through hybridisation of the fibre types.

Process Window for the Embedding of Eccentric Steel-Reinforcing Elements in the Discontinuous Composite Extrusion Process

The process of discontinuous composite extrusion offers the possibility for the centric and eccentric embedding of steel reinforcing elements into an aluminium profile. Thereby, the process is influenced by various parameters, which can lead to certain types of processes failures. Three characteristic types of process failures – cavities, local plastic deformation and rotation – have been identified. According to these influencing factors and based on the process window for the discontinuous centric embedding of cylindrical reinforcing elements in rods, a process window for the eccentric embedding of steel reinforcing elements was developed.

Assessment of Fiber Stress Based on Elastoplastic Analysis in Discontinuous Composite Materials

An elastopalstic analysis of the micromechanical approach is performed to investigate the stress transfer mechanism in a short fiber reinforced composites. The model is based on the New Shear Lag Theory (NSLT) which was developed by considering the stress concentration effects that exist in the matrix region near fiber ends. The unit cell model is selected as the Representative Volume Element (RVE) for the investigation of longitudinal elastoplastic behavior in discontinuous composites. Thus far, it is focused on the detailed description to predict fiber stresses in case of the behavior of elastoplastic matrix as well as elastic matrix. Slip mechanisms between fiber and matrix which normally take place at the interface are considered for the accurate prediction of fiber stresses. Consequently, onset of Slip points is determined analytically and it showed a moving direction to the fiber center region from the fiber tip as the applied load increases. It is found that the proposed model gives the more reasonable prediction compared with the results of the conventional model (SLT).