**5. Summary**

The FLD in the core and shell regions of PP20GF injection molded plaques was measured with a new approach expanding on a currently used fiber length measurement technique. The approach involves extracting a single shell layer by grinding material away in a controlled manner and measuring its FLD. The FLD in the core can then be determined indirectly. Comparison with the through-thickness FLD from mold filling simulations does not show a good quantitative agreement. Stiffness predictions show that the longitudinal and transverse Young's modulus suffer little change when considering the through-thickness changes in FLD rather than a constant value over the whole thickness. This agrees with stiffness predictions from Tandon and Weng and experimental results collected by Schemme, as in both cases the tensile modulus levels-off when the fiber's aspect ratio approaches 50.

**Author Contributions:** A.B.S. conceived and designed the experiments, analyzed the data, and wrote the paper. T.O. supervised the project and was involved in all stages of the research. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by the National Science Foundation under Grant No.1633967.

**Acknowledgments:** The authors thank SABIC® for their ongoing support and collaboration with our research group and their material supply.

**Conflicts of Interest:** The authors declare no conflict of interest.
