Analysis of syntactic foam – GFRP sandwich composites for flexural loads
The use of glass microballoon (GMB) — epoxy syntactic foams as a sandwich core material is studied. The skins and foam core are fabricated and joined instantaneously unlike the procedures followed in the previous studies. Each successive layer of the sandwich is fabricated when the previous layer is in a semi-gelled state. These sandwich samples are characterized for their properties under flexural loading. The failure modes and mechanical properties are carefully investigated. The change in fabrication technique results in a significant increase in the load bearing pattern of the sandwich. In earlier studies, debonding was found to occur prematurely since the bonding between the skins and core is the weakest plane. Using the current technique, core cracking occurs first, followed by skin fiber breaking and debonding happens at the end. This ensures that the load carrying phase of the structure is extended considerably. The sandwich is also analytically studied using Reddy’s higher order shear deformation theory. A higher order theory is selected as the sandwich can no longer be considered as a thin beam and thus shear effects also need to be considered in addition to bending effects.
Loading Effect of Hollow Glass Microsphere (HGM) and Foam Microstructure on the Specific Mechanical Properties and Water Absorption of Syntactic Foam Composite
AbstractEpoxy syntactic foams (SF) filled with hollow glass microspheres (HGM) were prepared by simple resin casting method and characterization in this study. The effect of varying the amount of HGM on the specific mechanical and water absorption properties of SF composites were investigated. Five different composition of SF (SFT60-0.5 to SFT60-2.5) were compared with the neat epoxy matrix. The wall thickness of the microballoons differ because of its different percentile size distribution (10th, 50th and 90th), which reflects in its density variation. The results show that the specific tensile and flexural strength increases with an increasing filler (HGM) content. The density of SF filled with HGM reduces with increasing volume fraction of filler content. Scanning electron microscopy was done on the failed samples to examine the fractured surfaces. The water absorption capacity of the SF was also investigated as it relates to the HGM volume fraction variation. All the syntactic foam composition shows a better diffusion coefficient capacity than the neat epoxy resin. This makes it applicable in structural purposes and several marine application products such as Autonomous Ultimately Vehicle (AUV).
Processing and compressive strengths of syntactic foams with and without fibrous reinforcements
Syntactic foam composites containing 0, 0.9, 1.76, 2.54, 3.54, and 4.5 vol % of E-glass fibers in the form of chopped strands were fabricated and subjected to compression testing. It was found that the compressive strength values generally increased with fiber content except for the 3.54% fiber-bearing cast slab, which recorded lower values. This lone exception was due to the difference in processing route adopted in fabricating this particular fiber-bearing foam. Also noticed was the fact that the compressive strength of the 0.9 vol % fiber-bearing system was lower compared to the fiber-free system. This was correlated to the higher level of void content noticed with this fiber-bearing foam compared to that seen in the unreinforced foam.