Compared to thermosetting resins, thermoplastic polymers offer many advantages as fiber reinforced composite matrices, such as excellent toughness, superior corrosion resistance, weldability, and recyclable, etc. However, the processibility of thermoplastic composites is commonly considered as a challenge because of the high viscosity of polymer melts (e.g., polypropylene, polyetheretherketone, etc.), which remarkably hinders their applications. Using low viscosity and in situ polymerizable thermoplastic resins to manufacture continuous fiber reinforced thermoplastic composites have been deemed as a cost-effective emerging approach to surpass the processibility challenges. Therefore, this paper presents an overview of advancement in the engineering, high-performance and room-temperature-processible liquid methyl methacrylate (MMA) resins and their composites up to date. First, the polymerization behavior and kinetic modeling of the MMA resins are reviewed, and the effects of initiators on the polymerization are summarized. In the second part, the pultrusion process and modeling including impregnation, temperature distribution and pulling force are discussed. Next, the mechanical properties and durability of the carbon fiber-, glass fiber-reinforced MMA-matrix composites are presented. Finally, the challenges of the preparation and application of the MMA-matrix composites are identified.

Traditional adherend surface treatment techniques such as grit blasting, acid etching, phosphating and primer treatments alone are often inadequate for maintaining interfacial bond durability of adhesively bonded joints. Therefore, the existing interfacial bonds between epoxy adhesive and the adherend should be strengthened. Tannic acid (TA) is a plant-based polyphenol that is inexpensive and easily available in nature. Its potential as an additive to improve the interfacial bond durability of epoxy adhesives has not been studied adequately. In the present study, an additive (TA-AGE) was synthesized by grafting allyl glycidyl ether (AGE) onto phenolic hydroxyl groups of TA. With 1 wt% TA-AGE additive in the epoxy, the single lap shear strength improved by 37%. Further, accelerated aging studies were performed to understand the impact of water uptake on the mechanical and viscoelastic properties and interfacial bond durability of the epoxy with 1 wt% TA-AGE additive. TA-AGE modification can increase hydrophilicity and enhance the water uptake characteristics of epoxy. This can negatively impact its mechanical properties and glass transition temperature (T g ) due to plasticization effects. Nevertheless, Boeing wedge test and single lap shear tests reveal that the strengthened interfacial bonds to steel adherends with the additive were robust and durable.