ORIGINAL RESEARCH A treatise on multiscale glass fiber epoxy matrix composites containing graphene nanoplatelets Usama Zaheer 1 & Aqeel A. Khurram 2 & Tayyab Subhani 1 Received: 15 May 2018 /Accepted: 8 August 2018 /Published online: 29 August 2018 # Springer Nature Switzerland AG 2018 Abstract Multiscale composites of epoxy matrix containing glass fibers and graphene nanoplatelets were prepared to investigate the effect of incorporating nanoplatelets upon the microstructural evolution and mechanical properties of the composites. Ozone- functionalized nanoplatelets were uniformly mixed in epoxy before incorporating glass fabric in the composites and processed through vacuum molding. Three different loadings of nanoplatelets were used, i.e., 0.1, 0.3, and 0.5 wt%, while the fraction of glass fibers was kept constant at ~ 60 wt%. The dispersion of nanoplatelets was witnessed using scanning electron microscopy, while mechanical characterization was performed using tensile, compression, flexural, and shear tests. Homogeneous dispersion of nanoplatelets increased mechanical properties of the composites, i.e., tensile, compression, flexural, and shear strengths up to 75, 30, 23, and 36%, respectively; similar trend in moduli values was observed, i.e., 116, 126, and 38%, respectively. The increased bonding between glass fibers and epoxy matrix due to nanoplatelets was found to be the possible reason of the increase in mechanical performance of multiscale composites along with the generation of a nanocomposite of GNP-reinforced epoxy to act as the matrix. Keywords Multiscale composite . Graphene nanoplatelets . Epoxy . Functionalization . Mechanical properties 1 Introduction Fiber reinforced polymer matrix composites have been used extensively in aerospace, automotive, marine, and sports in- dustries due to their excellent mechanical properties together with low-cost and inexpensive manufacturing [1]; chemical and corrosion resistance along with low weight are their addi- tional attributes [2]. Although the use of conventional mi- crometer size fibers, i.e., carbon, glass, and aramid, in a vari- ety of forms, i.e., short, long, woven, or braided, provides flexibility to prepare composites with tailored properties [3–5], these two-component composite systems (reinforce- ment and matrix) have otherwise attained their optimum prop- erties, which can be improved by using superior quality reinforcement or matrix in addition to sizing’ s. A different approach to enhance the existing properties of these traditional composites is to introduce a third component as an additional reinforcement, i.e., nanofillers, to prepare novel composites called as multiscale composites [6, 7]. The literature indicates the pronounced effect of UV/Ozone treatment on the mechanical properties of epoxy composites [8, 9]. The treatment of GNPs using UV/ozone not only intro- duces oxygen containing functional groups like hydroxyl and carbonyl groups on the surface of GNPs but also removes loosely bound organic functional groups, which results in sharp boundaries of GNPs thereby improving the bonding with epoxy which ultimately leads to higher mechanical prop- erties [8]. The dispersion of GNPs in epoxy composites is crucial for enhancement of thermal, electrical and mechanical properties; however, different process routes were developed in the past to improve dispersion of GNPs in epoxy matrix like functionalization of nanoparticles, ultrasonication, and high- speed shear mixing [8, 10]. Although carbon fibers offer better mechanical properties in composites than other fibers, their high-cost restricts their widespread applications in comparison to glass fibers [11]. Not only for conventional applications like structure of * Usama Zaheer usama1on1@hotmail.com 1 Composite Research Center, Department of Materials Science and Engineering, Institute of Space Technology, Islamabad, Pakistan 2 Laboratory for Advance Materials Processing, NCP Complex, Islamabad, Pakistan Advanced Composites and Hybrid Materials (2018) 1:705–721 https://doi.org/10.1007/s42114-018-0057-y