This study provides an economical and effective method to improve the interlaminar properties of carbon fiber-reinforced polymers (CFRPs) using aluminum trihydroxide (ATH) microparticles. ATH microparticles are cheap and are expected to show good affinity to epoxies in the matrix and sizing agents of the carbon fibers owing to the presence of three hydroxyl groups. In addition, ATH particles are reported to improve the mechanical properties of polymers when used as the reinforcement. In this study, ATH microparticles of various sizes, 1.5, 10, and 20 μm, were used to improve the interlaminar properties of the CFRPs. ATH particles with a size of 1.5 μm improved the tensile properties of the ATH/epoxy resin and did not significantly alter the curing behavior. The interfacial adhesion between the carbon fiber and the epoxy resin was also improved, and the impregnation of the resin mixture remained similar to that of the neat resin, resulting in no significant void and defect formation. Considering the above results, the resulting 1.5 μm ATH-reinforced CFRP showed improved interlaminar properties compared to CFRP without ATH. However, 10 and 20 μm ATH-reinforced CFRPs showed deteriorated interlaminar properties due to the diminished tensile properties of the resin itself and resin impregnation, which resulted in more voids and defects, despite the interfacial adhesion between the fiber and the matrix resin.

Improvement of interlaminar properties of carbon fiber-reinforced epoxy composites using aluminum trihydroxide
    Abstract
    1 Introduction
    2 Experimental
        2.1 Materials
        2.2 Preparation of ATHepoxy resins and ATH-reinforced CFRPs
        2.3 Gel time and tensile properties of prepared ATHepoxy resins
        2.4 Evaluation of interfacial shear strength and wetting behavior of prepared ATHepoxy resins on CFs
        2.5 Evaluation of interlaminar shear strength of ATH-reinforced CFRP with various particle sizes
    3 Results and discussion
        3.1 Curing behavior and tensile properties of prepared ATHepoxy resins
        3.2 Interfacial adhesion to carbon fiber and wetting behavior of prepared ATHepoxy resin on CF tow
        3.3 Interlaminar shear strength of ATH-reinforced CFRPs with various ATH particle sizes
    4 Conclusions
    Acknowledgements 
    References

• Dong‑Jun Kwon(Polymer Resin Team, Korea Dyeing and Finishing Institute)
• Sung‑Min Park(Polymer Resin Team, Korea Dyeing and Finishing Institute)
• Il‑Jun Kwon(Polymer Resin Team, Korea Dyeing and Finishing Institute)
• Joung‑Man Park(Department of Materials Engineering and Convergence Technology, Gyeongsang National University)
• Euigyung Jeong(Department of Textile System Engineering, Kyungpook National University)