Experimental Investigation into the Uncertainty of the Mechanical Properties of Short Fibre-Reinforced Polymers

The present study is a comprehensive experimental investigation of the uncertainties in the mechanical response of short fibre-reinforced composites. The reference material investigated is a short glass fibre-reinforced phenolic resin matrix material, manufactured in a thermoset injection-moulding process. The mechanical material response was investigated in experiments on three different scales, considering ISO-size, miniature, and micro tensile samples. Further to the tensile experiments, compressive and shear tests were performed on macroscopic samples. Experiments on breadboard samples featuring more complex stress and deformation states complete the study. The injection-moulding process was found to control the basic fibre orientation. However, the nominal local fibre orientation distribution is superimposed with a pronounced local uncertainty. This microstructural uncertainty strongly affects the uncertainty in the local mechanical properties as well as variations between samples taken from identical positions in different but nominally identical plates.