Successful utilization of thermosetting resins as ablative materials for heat shields in thermal protection systems (TPS) has newer contemporary materials, surpassing the conventional resins in terms of thermal and physical properties The present study demonstrates similar progress in ablative heat shielding materials, putting forward capable replacements for existing phenolic system A novel three-dimensional network composed of a dihydric resorcinol formaldehyde (RF) has been synthesized successfully by modification with boric acid via an effortless and facile polymerization technique The ablation and thermal properties were investigated with primary and cheap, yet effective test methods like the oxy-acetylene flame test, which explored the ablation rate in terms of mass loss and dimensional change, showing 40% and 70% curtailment respectively X-Ray diffraction studies confirm the formation of insulative, turbostratic, carbonaceous char formed upon resin pyrolysis with peaks at 24° and 44° attributing to (002) and (100) for turbostratic carbon formed during pyrolysis FTIR studies reveal change in the intensity and shifts in the peaks for pristine RF for the boric acid modified RF including stretch vibrations at 1429 and 1380 cm−1 corroborating modification of the ring Atomic Force Microscopy showed the surface roughness which up surged with an increase in the concentration of boric acid in the system, making the composite sensitive to mechanical depletion due to increase reactivity Interesting morphologies of the sample after ablation were observed with FESEM exposing glassy nanospheres of borate in the periphery and porous char of the depleted zone Pristine RF has a char yield of 42%, which increased to 68% for 50 wt% of boric acid in RF at 800 °C, quantified by the TGA studies Mathematical models and energy balance equations were idealized for the exchange in energies at the surface of the ablator The results determined that the modification of the 3D network of the resin justifies its competency to replace conventional materials demonstrating augmented ablation resistance with faster reaction mechanisms

Reticulated three-dimensional network ablative composites for heat shields in thermal protection systems

Improved mechanical responses of GFRP composites with epoxy-vinyl ester interpenetrating polymer network

http://prr.hec.gov.pk/jspui/bitstream/123456789/7982/1/Complete%20Ph.D%20Thesis%20Dildar%20Ali%20Lakho%20final1.pdf

Study of cure kinetics, chemorheological and thermal behaviour of different formulations of DGEBA epoxy

A 3D thermal response model is developed to evaluate the thermal behavior of glass fiber/phenolic composite exposed to heat flux on one side. The model is built upon heat transfer and energy conservation equations in which the heat transfer is in the form of anisotropic heat conduction, absorption by matrix decomposition, and diffusion of gas. Arrhenius equation is used to characterize the pyrolysis reaction of the materials. The diffusion equation for the decomposition gas is included for mass conservation. The temperature, density, decomposition degree, and rate are extracted to analyze the process of material decomposition, which is implemented by using the UMATHT(User subroutine to define a material's thermal behavior ) and USDFLD(User subroutine to redefine field variables) subroutines via ABAQUS code. By comparing the analysis results with experimental data, it is found that the model is valid to simulate the evolution of a glass fiber/phenolic composite exposed to heat flux from one side. The comparison also shows that longer time is taken to complete the pyrolysis reaction with increasing depth for materials from the numerical simulation, and the char region and the pyrolysis reaction region enlarge further with increasing time. Furthermore, the decomposition degree and temperature are correlated with depths, as well as the peak value of decomposition rate and the time to reach the peak value.

Simulation of Thermal Behavior of Glass Fiber/Phenolic Composites Exposed to Heat Flux on One Side.

Blends of cyanate ester and phthalonitrile–polyhedral oligomeric silsesquioxane copolymers were prepared, and their cure behavior and properties were compared via differential scanning calorimetry (DSC) analysis, thermogravimetric (TG) analysis, dynamic mechanical analysis, Fourier-transform far-infrared (FTIR) spectroscopy, and rheometric studies. The copolymer blends showed high chemical reactivity, low viscosity, and good thermal stability (TG temperatures were above 400 °C). The glass-transition temperature of the blends increased by at least 140 °C compared to cyanate ester resin. The blends are suitable for preparing carbon-fiber-reinforced composite materials via a winding process and a prepreg lay-up process with a molding technique. The FTIR data showed that the polymerization products contained triazine-ring structures that were responsible for the superior thermal properties.

https://www.mdpi.com/2073-4360/11/1/54/pdf

M.M. Raj

Papers

Glass fiber reinforced composites of phenolic–urea–epoxy resin blends