Understanding the Effect of Interfacial Interphase on the Elastic Response of Hollow Glass Microsphere Reinforced Microcomposites

The hollow glass microspheres (HGMS) has been recently used in the fabrication of low-density polymeric composites due to rather high stiffness nature of the fillers together with their lightweight that in turn results in the development of micro-composites of engineered properties with enhanced mechanical properties. Interfacial interactions at the filler/polymer interface control the load transfer and, thus, bulk properties of composites leading to unpredictable performance of composites embedded with inclusions. Nevertheless, useful analytical models are required to estimate the mechanical behavior of the HGMS based composites with the incorporation of the effect of interfacial interactions and possible agglomeration of fillers. No studies so far have reported the analytical modeling of HGMS reinforced thermosetting composites emphasizing the role of the interphase shaped at the vicinity of fillers.  This study aims at the fabrication of 0-20 wt% HGMS/polyester micro-composites followed by micromechanical modeling of the fabricated parts whilst the effect of the interphase region is emphasized by models modification. The results indicated a strong correlation between the interphase characteristics and Young’s modulus of the specimens revealing the dependency of the modulus on the thickness and modulus of the interphase as well as the level of agglomeration and interfacial debonding of the HGMSs. The results demonstrated that with considering no interphase, the models underestimate the modules of the parts, which suggests the presence of stiff interphase around the HGMS governed by changes in the interfacial cross-link density of the parent polymer as hypothesized supported by the mechanical response of the parts.