This research project investigates the relationship between filler dispersion in polymer matrices and the resulting structural characteristics of composite materials. Polymer composites are widely used in engineering fields such as aerospace and mechanical engineering due to their lightweight structure and favorable mechanical properties. However, the performance of these materials strongly depends on how uniformly fillers are distributed within the polymer matrix. The study reviews different types of fillers used in polymer composites and analyzes how their size, shape, and distribution influence the mechanical behavior of composite materials. Particular attention is given to the role of filler dispersion in determining tensile, flexural, and impact properties of reinforced polymer systems. The research also focuses on modern non-destructive testing techniques used to analyze internal structures of composite materials. Among these methods, X-ray computed tomography (CT) is highlighted as an effective technique for three-dimensional visualization and characterization of internal microstructures without damaging the material. Additional inspection approaches such as shearography, infrared thermography, ultrasonic testing, and eddy current array methods are also discussed in the context of defect detection and structural analysis. The findings emphasize that achieving uniform filler dispersion remains a significant challenge in polymer composite manufacturing. Poor dispersion may lead to agglomeration, void formation, and reduced mechanical performance. Understanding these microstructural characteristics through advanced imaging techniques can support better material design and improved reliability of composite systems in engineering applications.