Analysis of Particle Variation Effect on Flexural Properties of Hollow Glass Microsphere Filled Epoxy Matrix Syntactic Foam Composites

Syntactic foam made from hollow glass microspheres (HGM) in an epoxy matrix has proven to be a good material with a strong structural strength. Understanding filler particle size variation is important in composite material formation, especially in syntactic foam, because of its numerous applications such as aerospace, marine, and structural purposes. In this present work, the effects of particle variation in different sizes (20-24 µm, 25-44 µm, 45-49 µm, and 50-60 µm) on the mechanical properties of the syntactic foam composites with a focus on flexural strength, modulus, and fracture surfaces are investigated. The particle sizes are varied into five volume fractions (5, 10, 15, 20, and 25 vol%). The results show that the highest flexural strength is 89 MPa at a 5 vol% fraction of 50-60 µm particle size variation with a 69% increase over the neat epoxy. This implies that the incorporation of HGM filler volume fraction and size variation has a strong effect on the flexural strength and bending modulus of syntactic foam. The highest particle size distribution is 31.02 at 25-44 µm. The storage modulus E' increased at 30 °C, 50 °C, and 60 °C by 3.2%, 47%, and 96%, respectively. The effects of wall thickness and aspect ratio on the size of the microstructure, the fracture surfaces, and the viscoelastic properties are determined and reported accordingly.

Preparation and Properties of Epoxy/Multiwalled Carbon Nanotube Nanocomposite Foams with an Alternating Layer Structure

Multilayered epoxy/multiwalled carbon nanotube (EP/MWCNT) composite foams with a density of 0.713 g/cm³ were prepared through the chemical foaming of laminated epoxy sheets in a mold with a fixed cavity. The difference in cell morphology and properties between adjacent layers in the multilayer foams (two- and four-layer) was tuned by MWCNT or chemical foaming agent (CFA) concentration. It was found that the storage modulus and microwave-absorbing ability of the multilayered EP/MWCNT foams were strongly associated with the loading direction, the thermal diffusivity was slightly direction-dependent, and the electromagnetic interference (EMI) shielding effectiveness (SE) was direction-independent. In addition, as the layer number increased, the mechanical, thermal, and electrical conductivity properties and EMI shielding performances of the multilayered composite foams showed different change tendencies. These results indicated that the effect of the multilayer structure on the properties of composite foams was different when they underwent force, heat, or electromagnetic microwave, and the underlying reasons were investigated in detail.

A novel epoxy-functionalized hyperbranched polysiloxane (HPSi) endowing methyl phenyl silicone resin (Si603)/epoxy systems with enhanced compatibility and fire retardancy performance

A novel hyperbranched polysiloxane (HPSi) with a great amount of epoxy groups was synthesized as a compatibilizer of epoxy resin (EP)/methyl phenyl silicone resin (Si603) blends.

Performance improvement of flame-retarded poly(butylene terephthalate)/aluminum diethylphosphinate composites by epoxy-functional polysiloxane

An epoxy-functional polysiloxane (EPM) was employed for improving the performance of flame-retarded poly(butylene terephthalate)/aluminum diethylphosphinate (PBT/AlPi) composites. The effect was investigated by UL-94 test, limiting oxygen index, mechanical test, torque rheometer measurement, differential scanning calorimetry, dynamic mechanical analysis, and heat distortion temperature. An obvious increase in torque evolution of the PBT/AlPi composite during processing was associated with chain-extending, branching, and cross-linking reaction by the combination of EPM. The addition of 0.6 wt% EPM remarkably enhanced not only the mechanical properties but also the flame retardancy and heat resistance of the PBT/AlPi composite. A high-performance PBT/AlPi composite was developed by virtue of EPM.

A review of the feasibility of lightening structural polymeric composites with voids without compromising mechanical properties

High performance polymer-fiber composites are high strength, low weight materials that have many applications, many of which would benefit from a decrease in weight, without a decrease in material properties. Generally, the fibers serve as the main load carriers, while the matrix serves to distribute load and protect the fibers from the environment. Thus, it is postulated that if the volume fraction of matrix is reduced, while still ensuring complete wetting of the fibers by the matrix, the per unit weight, i.e., specific, mechanical properties could be improved. This can be done by introducing small, spherical bubbles. Given the small average inter-fiber distance and assuming that the bubbles must not interact with the surface of the reinforcements the bubble diameter would need to be less than 1 μm. Introducing bubbles this small and ensuring that they do not form, or become attached, on the surface of the reinforcement are significant challenges. Two methods to produce such bubbles and the effect of these bubbles on mechanical properties of neat resins are reviewed: the addition of hollow spherical fillers, called microballoons, and the creation of bubbles from blowing agents. Microballoons in resins are a class of materials called syntactic foams. Although commercial microballoons are too large, smaller diameters can be made and could be used to reduce the weight of a reinforced composite on the order of 10%. The use of a physical blowing agent to produce bubbles in a composite is also considered. However, traditional polymer foaming techniques may be inadequate, as nucleation on the reinforcing phase is likely, and the bubbles formed are generally too large, so the use of blowing agent wells is considered. Blowing agent wells are discontinuous regions made from copolymer micelles or immiscible polymers that act as reservoirs of blowing agent. Additionally, the use of nano-sized materials for use as heterogeneous nucleation sites and secondary reinforcement of the matrix is also considered. Bubbles made from blowing agent could reduce the weight slightly more than using hollow spheres, but the reduction would also be of the order of 10%.