Microballoon Wall Thickness Effects on Properties of Syntactic Foams

Abstract

A novel approach for changing the density of syntactic foams, while keeping the microballoon (hollow particles) volume fraction constant, is adopted in this work. This is achieved by selecting microballoons of the same size but with different wall thickness. Five types of microballoons are selected to fabricate syntactic foams. All the types of microballoons have about 40 mm mean particle sizes, but different wall thicknesses. This approach allows to maintain the same volume fractions of constituents and interfacial area while changing the density of syntactic foams. The fabricated syntactic foams are tested for their compressive properties in accordance to the ASTM D 695-96 standard. The results of the experimental investigation show a strong dependence of the compressive properties and the fracture characteristics of syntactic foams on the microballoon wall thickness. Shear cracking followed by cracking under secondary tensile stresses has been observed as the fracture mode. The present approach is found to be more effective than changing the microballoon volume fraction to change the syntactic foam density as it considerably increases the strength to the weight ratio.

Thermal expansion behavior of hollow glass particle/vinyl ester composites

“…Previous studies have characterized the mechanical properties of syntactic foams with respect to the properties and volume fraction of the filler particles [1]. Wall thickness and volume fraction of hollow particles (microballoons) are found to be very effective in tailoring the mechanical properties of syntactic foams [2]. These lightweight materials are suitable for weight saving applications in aerospace structures [3], undersea pipeline insulation [4], and electronic coating and packaging [5] because of their high compressive properties and low moisture absorption compared to other lightweight materials such as foams containing gas porosity.…”

Enhancement of Energy Absorption in Syntactic Foams by Nanoclay Incorporation for Sandwich Core Applications

“…Both these methods lead to increase in syntactic foam density also. However, the second method is found to be much more effective as it increases compressive strength and modulus with least increase in density [11]. The second method gives additional advantage of varying only one material parameter, microballoon wall thickness, giving better control over the properties of syntactic foams.…”

Development and characterization of epoxy syntactic foam filled with epoxy hollow spheres

“…Syntactic foams can be classified as closed pore foams, since the porosity in these materials exists in the form of discrete hollow particles. The closed pore structure gives advantages of excellent mechanical properties, higher strength, low density as well as lower moisture absorption compared to the open cell foams [9]. Moreover, the usage of syntactic foams as core material in sandwich structure applications ensures high rigidity and compressive strength of the sandwich structures compared to utilization of other polymeric foams [10].…”

“…Moreover, the usage of syntactic foams as core material in sandwich structure applications ensures high rigidity and compressive strength of the sandwich structures compared to utilization of other polymeric foams [10]. Several studies on mechanical properties of syntactic foams [7,[11][12] and their sandwich structures can be found in numerous published literature [9,[13][14]. Syntactic foams can be defined as composite materials in which hollow microspheres, or other small hollow particles, are randomly dispersed in a matrix [15].…”

“…On the other hand, the matrix material binds the microspheres and gives the composite component its shape and determines the quality of its surface finish. Suitable materials can be selected for the matrix materials such as polymers, ceramics or metals [9]. Polymer matrices are commonly used for composites in commercial and high performance aerospace applications.…”