In recent years, due to the rapid development of industrial lightweight technology, composite
materials based on fiber reinforced plastics (FRP) have been widely used in the industry. However, the
environmental impact of the FRPs is higher each year. To overcome this impact, co-injection molding
could be one of the good solutions. But how to make the suitable control on the skin/core ratio
and how to manage the glass fiber orientation features are still significant challenges. In this study,
we have applied both computer-aided engineering (CAE) simulation and experimental methods to
investigate the fiber feature in a co-injection system. Specifically, the fiber orientation distributions
and their influence on the tensile properties for the single-shot and co-injection molding have been
discovered. Results show that based on the 60:40 of skin/core ratio and same materials, the tensile
properties of the co-injection system, including tensile stress and modulus, are a little weaker than
that of the single-shot system. This is due to the overall fiber orientation tensor at flow direction (A11)
of the co-injection system being lower than that of the single-shot system. Moreover, to discover and
verify the influence of the fiber orientation features, the fiber orientation distributions (FOD) of both
the co-injection and single-shot systems have been observed using micro-computerized tomography
(µ-CT) technology to scan the internal structures. The scanned images were further utilizing Avizo
software to perform image analyses to rebuild the fiber structure. Specifically, the fiber orientation
tensor at flow direction (A11) of the co-injection system is about 89% of that of the single-shot system in
the testing conditions. This is because the co-injection part has lower tensile properties. Furthermore,
the difference of the fiber orientation tensor at flow direction (A11) between the co-injection and the
single-shot systems is further verified based on the fiber morphology of the µ-CT scanned image.
The observed result is consistent with that of the FOD estimation using µ-CT scan plus image analysis.
