Investigation of the effects of additives on the mechanical properties and impact strength of polymer based thermoset composites

The usage of composite materials in various industrial applications, especially in aviation, marine and automotive sectors, is increased widely, due to high strength properties compared to their weights. To increase mechanical properties of a composite material, a variety of micro and nano sized additives are added into the matrix material. In this study, ceramic nanoclay, polyamide microspheres and carbon nanotubes are used as an additive to plain woven and biaxial non crimp E-glass fabric reinforced epoxy resin composites. Mechanical properties and the low velocity impact behavior of Glass Fiber Reinforced Epoxy (GFRE) composites with the addition of organic intercalated nanoclay, spheroidal powder of polyamide nanoparticles and short multiwalled carbon nanotubes individually and together were investigated experimentally. The specimens are prepared from composite plates for tensile, compression, buckling and low velocity impact tests. The weight ratio of carbon nanotubes was 0.3%, while the weight ratio of the other additives was up to 2% of the epoxy resin-hardener system. In addition to this, these additives are tested when used together with same ratios and the effects of each mixture is compared. Composite laminates were manufactured using prepreg and hot-pressing techniques. With the addition of nanoparticles, an improvement of up to 27% in tensile strength, 10% in compressive strength and approximately 5% in buckling strength of the composites was observed. Impact tests were carried out at different energy levels from 10 J to 45 J up to complete perforation of the laminates. To evaluate the damage characteristics of the laminates, the results are interpreted in terms of loadtime, load-displacement, energy-time, and observation of the physical damages introduced. Addition of nanoparticles increased the peak load (up to 22.6%) and damage resistance (up to 40%) of the GFRE laminates altering damage mechanisms of the composite material from out of plane to in-plane direction at higher impact energy levels. As a result of these experiments, it is observed that mechanical properties and low velocity impact strength of the composites are improved remarkably with the help of the additive materials.