Abstract
The present study investigates the influence of fiber content on thermal properties of short silica fiber (SSF) reinforced modified resole resin (MRR) composites. For this purpose, different SSF loading composites were prepared: 40, 55, and 65 wt.%. The ablation resistance related to mass loss parameters was quantified by testing under an oxyacetylene flame up to 2300 °C for 30 s. The thermal conductivity of the composite was studied via experimental steady state technique. Thermal stability of the composite material was estimated by means of thermo-gravimetric analysis (TGA), both in air and nitrogen atmosphere. The ablated composite material was characterized by different techniques (XRD, FTIR, and SEM). The results showed that the backface surface temperature of SSF/MRR composites follows the typical variation curve, and linear ablation rate, mass ablation rate, and char yield decrease with increasing silica fiber content. This confirms that 55 and 65 wt.% SSF loading exhibited the best anti-ablation performance and the lowest percentage of char yield. XRD and FTIR analysis of the ablated specimen zone showed the absence of new phase. The thermo-gravimetric analysis confirmed the thermal resistance of SSF/MRR composites in comparison with MRR matrix and the decrease of char with increasing SSF loading. The thermal conductivity of these composites was significantly enhanced by the SSF into the modified resole matrix. This thermal conductivity follows both the rule of mixture and Maxwell models. The overall thermal characteristics of the SSF/MRR composites meet most of the necessary high temperature application criteria.
Highlights
Fiber-reinforced composites have received much attention as ablative materials for aerospace applications in recent years (Eslami et al 2015)
These results show that the back surface temperature of 40 wt.% composite specimens, for example, is about 6 times and 4 times higher than those of 65 wt.% and 55 wt.% composite specimens, respectively
It is observed that BACK-FACE TEMPERATURE PROGRESSION (BTP) was reduced with increasing short silica fiber (SSF) loading in the SSF/modified resole resin (MRR) composites
Summary
Fiber-reinforced composites have received much attention as ablative materials for aerospace applications in recent years (Eslami et al 2015). The choice of reinforcing fiber and matrix depends upon various factors, among which strength, thermal stability, load bearing capability, and most importantly the type of envisaged application. Ablative composites are those materials that sacrifice themselves to protect the inner hardware during vehicles and spacecraft’s reentry from ultrahigh temperature and supersonic environments (Hu et al 2014). The ablation of a material depends on its inherent properties and on extrinsic conditions such as thermal, chemical, and mechanical factors related to theoretical or practical environment variables.
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