Zulzamri Salleh

Analysis of Stress Concentration Factor for Tensile Characteristics of Syntactic Foam Using Finite Element Method

This paper presented the stress concentration factor (SCF) around the half circular edge of tensile specimens made of syntactic foam using finite element software Strand7 software. The study is a preliminary effort, which investigates the effect of variations of crack geometry on the stress concentration factor on a tensile specimen subjected to a constant, uniform, uniaxial tensile load. The material property is graded for varying Young’s Modulus and Poisson’s Ratio with different composition of glass microballoons. Finally, a uniform pressure is applied at the top and the model is constrained with symmetric boundary conditions at the left and bottom. As the result, these numerical results for both SCF experimental and simulation model are compared to those obtained from analytic fracture mechanics procedures and are found to be varied. In addition, the SCF is sensitive to the modulus of elasticity, particularly for lower composition weight percentage (wt.%), while it is also varied with the different weight percentage (wt.%) of glass microballoons, which is led by 2 wt.% specimen.

Determination of coefficient thermal expansion of glass microballoon/vinyl ester syntactic foams

The coefficient thermal expansion, alpha (CTE) of glass microballoon/vinyl ester syntactic foam was determined using dimensional changes of a temperature gradient plot. The CTE was measured and found to be up to 53-63% lower than the vinyl ester resin matrix when mixing different weight percentages of the glass microballoon ranging from 2 wt.% to 10 wt.% using a thermomechanical analyzer (TMA). The results of CTE show that it has a strong relationship with the syntactic foam density (rho), radius ration (eta), cavity porosity (phi y) and matrix porosity (phi mu) within the parameters entered. Experimental results show that the CTE decreases when glass microballoons are added into the composites measured at different temperatures ranging from 30-70°C. The CTE from the experimental results were also compared with Turner’s modification model for composites for its suitability for thermal expansion of syntactic foams. The results indicate that Turner’s modification model exhibits a close correlation with the reduction of up to 80% of CTE based on experiment.

Thermogravimetry analysis on fused borosilicate syntactic foams

Fused borosilicate/vinyl ester syntactic foams mostly used for thermal stability in many applications are considered to be characterised for their properties in higher temperature condition. Therefore, higher temperature characteristics need to be explored with respect to physical parameters such as porosity and void content. The filler, also known as glass microballoons, was incorporated in vinyl ester resin matrix in 2wt%, 4wt%, 6wt.%, 8wt.% and 10wt.%. These composites are characterised and degraded to examine the onset temperature, Tonset, peak temperature, Tpeak and end temperature, Tend using thermogravimetric analysis (TGA) method. The results for Tonset showed an increment while Tend and Tpeak showed decrement when glass microballoons were added in syntactic foams. Based on TGA data, they exhibited excellent thermal stability, showing 5% weight loss at 380-450 °C. Glass transition temperature (Tg) decreased when more glass microballoons were added, and also related to the effect on the physical pr...

Compressive behaviour of low density polymeric syntactic foams

The combinations of polymer resin and glass microballoon are the main materials used to produce syntactic foams. Syntactic foam is a lightweight material that has good mechanical properties and is commonly used as a component for structural materials in civil construction, aerospace and marine applications. Hence, it should have suitable mechanical properties, particularly good compression behaviour. In the present study, the results obtained from compression tests are compressive strength, elastic modulus and specific compression that decrease when increasing of glass microballoon contents (2.0 wt.%, 4.0 wt.%, 6.0 wt.%, 8.0 wt.% and 10.0 wt.%) and also neat resin. The highest strength value for compression testing is owned by 2.0 wt.% which is 88.9 MPa, while the lowest strength is 43 MPa that belongs to 10.0 wt.% of glass microballoon. This shows that the density and weight percentage of glass microballoon in these syntactic foams affect compression properties. Therefore, a further study should be conducted, which includes the effect of compressive failure mechanism.