Additive manufacturing of glass microfiber reinforced polymer composites using vat polymerization

The development of high-performance composite materials through filler reinforcement continues to attract attention due to growing demand for lightweight and mechanically robust components in engineering and aerospace sectors. This study investigates the fabrication and mechanical behavior of glass microfiber-reinforced high-temperature (HT) photo-curable resin composites using vat photopolymerization (VP) 3D printing. Milled glass microfibers were incorporated into the HT resin at 2.5 and 5 wt%, and a controlled high-shear mixing process was used to ensure uniform dispersion and reduce sedimentation — a common challenge in filled photopolymer systems. Composite specimens were printed using a commercial Formlabs Form 3 printer under standard conditions, highlighting the feasibility of producing fiber-reinforced composites without printer modifications. Post-printing heat treatment was applied to evaluate its influence on mechanical properties. Tensile testing revealed that the 2.5 wt% composite outperformed both the neat resin and the 5 wt% composite in strength and stiffness, demonstrating the significance of optimizing filler concentration. Fracture surface analysis using scanning electron microscopy (SEM) with back-scattered electron imaging indicated that excessive fiber content may lead to poor interfacial bonding and performance degradation. Although heat treatment modestly improved the strain-to-failure, it had a limited impact on modulus and strength, consistent with behavior observed in highly crosslinked photopolymers. This work underscores the viability of fabricating short-fiber composites through VP 3D printing and provides valuable insights into processing–performance relationships critical to structural applications.