Influence of chopped strand fibres on the flexural behaviour of a syntactic foam core system

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.

Warp-Knitted Spacer Fabric Reinforced Syntactic Foam: A Compression Modulus Meso-Mechanics Theoretical Model and Experimental Verification

In this study, a new type ternary composite, called warp-knitted spacer fabric reinforced syntactic foam (WKSF-SF), with the advantages of high mechanical properties and a lower density, was proposed. Then, a meso-mechanics theoretical model based on the Eshelby–Mori–Tanaka equivalent inclusion method, average stress method and composite hybrid theory was established to predict the compression modulus of WKSF-SF. In order to verify the validity of this model, compression modulus values of theoretical simulations were compared with the quasi-static compression experiment results. The results showed that the addition of suitable WKSF produces at least 15% improvement in the compressive modulus of WKSF-SF compared with neat syntactic foam (NSF). Meanwhile, the theoretical model can effectively simulate the values and variation tendency of the compression modulus for different WKSF-SF samples, and is especially suitable for the samples with smaller wall thickness or a moderate volume fraction of microballoons (the deviations is less than 5%). The study of the meso-mechanical properties of WKSF-SF will help to increase understanding of the compression properties of this new type composite deeply. It is expected that WKSF-SF can be used in aerospace, marine, transportation, construction, and other fields.

Compression Properties of Syntactic Foam Reinforced by Warp-knitted Spacer Fabric: Theoretical Compression Strength Model and Experimental Verification

In this study, a theoretical model based on the fiber buckling theory was established to predict the compression strength of a new type of syntactic foam, namely the syntactic foam reinforced by the warp-knitted spacer fabric (SF-WKSF). In order to verify the availability of this model, compression strength values of theoretical simulations were compared with the experiment results. The comparison results showed that the model can accurately simulate the compression strength values of different SF-WKSF samples with slight deviation. Finally, the causes of deviation was analyzed in detail.

Sound Absorption Properties of Syntactic Foam Reinforced by Warp-knitted Spacer Fabric

The aim of this study is to investigate the sound absorption properties of syntactic foam reinforced by warp-knitted spacer fabric (SF-WKSF). SF-WKSF was served as micro-perforated panel (MPP) sound absorber and different kinds of SF-WKSF samples were fabricated with warp-knitted spacer fabric (WKSF) of various surface layer structures and parameters. These parameters included inclination angle and fineness of spacer yarns, air cavity depth, microballoons types as well as microballoons contents. The acoustical behaviors of SF-WKSF and neat syntactic foam (NSF) were tested according to transfer function method. The results show that the SF-WKSF has better sound absorption properties compared to NSF. It is also demonstrated that the fabric surface structures, spacer yarn fineness and inclination angle, air cavity depth, microballoons contents and types have significant effects on the sound absorbability of SF-WKSF, meanwhile their performances of absorbing noise can be tailored by adjusting the parameters of spacer fabric, microballoons or air cavity.

Mussel-inspired polydopamine coated hollow carbon microspheres, a novel versatile filler for fabrication of high performance syntactic foams

Syntactic foams, which can be synthesized by mechanical mixing of hollow microspheres with a matrix material, are a special class of lightweight composite materials. Developing of high-performance syntactic foams remains challenges. In this work, a facile and environmentally friendly surface modification method employing polydopamine (PDA) as a surface treatment agent for hollow carbon microspheres (HCMs) was used, aiming to extend the application of syntactic foams to seldom touched areas. The PDA coating was used as a strategy for interfacial interaction enhancement and also as a platform for further metal coating meant for electromagnetic interference (EMI) shielding. The stronger interfacial interaction between microspheres and polymer matrix provided effective interfacial stress transfer, as a result of the syntactic foams with high strength to weight ratio. Furthermore, the PDA coating on HCMs served as a versatile platform for the growth of noble metals on the surface of PDA-HCMs. Silver nanoparticles was grown by PDA medium. The silver coated HCMs (Ag-PDA-HCMs) impacted the complex permittivity of the syntactic foams leading to high EMI shielding effectiveness (SE). The specific EMI SE reached up to 46.3 dB·cm(3)/g, demonstrated the Ag-PDA-HCMs/epoxy syntactic foam as a promising candidate for lightweight high-performance EMI shielding material.