Carbon Phenolic Research Articles

Mechanical, Thermal, and Ablative Properties of Silica, Zirconia, and Titania Modified Carbon-Phenol Ablative Composites

The effect of nanozirconia, nanotitania, and fumed silica on the mechanical, thermal, and ablation behaviour of carbon-phenolic (C-Ph) composites is investigated. The inorganic nanofillers at different loading percentage are used to prepare nano-C-Ph panels by the compression moulding technique. The dispersion of nanofillers is confirmed through SEM analysis. After manufacturing of C-Ph laminates, the mechanical properties such as tensile strength and hardness are evaluated and the effect of these fillers is investigated. Thermal conductivity, thermal erosion, and back wall temperatures were measured to understand the thermal and ablation behaviour of nano-C-Ph laminates. Additionally, the ablation mechanism is analysed by performing SEM analysis of partially and fully burnt composite laminates. The erosion resistance and burnout time of zirconia-C-Ph panels significantly improved with increase in filler loading percentage; however, the back wall temperature rises with filler loading. Titania-filled C-Ph panels show a better control over the back wall temperature but with a poor erosion control. Silica-filled composite panels have shown a balance between decreased back wall temperature with a reasonable erosion rate and burnout time.

Effect of organo-modified montmorillonite nanoclay on mechanical, thermal and ablation behavior of carbon fiber/phenolic resin composites

The mechanical, thermal and ablation properties of carbon phenolic (C-Ph) composites (Type-I) reinforced with different weight percentages of organo-modified montmorillonite (o-MMT) nanoclay have been studied experimentally. Ball milling was used to disperse different weight (wt) percentages (0, 1,2,4,6 wt.%) of nanoclay into phenolic resin. Viscosity changes to resin due to nanoclay was studied. On the other hand, nanoclay added phenolic matrix composites (Type-II) were prepared to study the dispersion of nanoclay in phenolic matrix by small angle X-ray scattering and thermal stability changes to the matrix by thermogravimetric analyser (TGA). This data was used to understand the mechanical, thermal and ablation properties of Type-I composites. Inter laminar shear strength (ILSS), flexural strength and flexural modulus of Type I composites increased by about 29%, 12% and 7% respectively at 2 wt.% addition of nanoclay beyond which these properties decreased. This was attributed to reduced fiber volume fraction (%Vf) of Type-I composites due to nanoclay addition at such high loadings. Mass ablation rate of Type-I composites was evaluated using oxy acetylene torch test at low heat flux (125 W/cm2) and high heat flux levels (500 W/cm2). Mass ablation rates have increased at both flux levels marginally up to 2 wt.% addition of nanoclay beyond which it has increased significantly. This is in contrast to increased thermal stability observed for Type-I and Type-II composites up to 2 wt.% addition of nanoclay. Increased ablation rates due to nanoclay addition was attributed to higher insulation efficiency of nanolcay, which accumulates more heat energy in limited area behind the ablation front and self-propagating ablation mechanisms triggered by thermal decomposition of organic part of nanoclay.

Experimental investigation of mechanical, thermal, and ablation performance of ZrO2/SiC modified C‐Ph composites

AbstractIn this study, an effort has been made to improve the mechanical, thermal, and ablation performance of carbon‐phenolic (C‐Ph) composites. The ZrO2, SiC, and ZrO2/SiC hybrid fillers were synthesized using sol‐gel method followed by individual incorporation into C‐Ph composites. The thermal stability and flexural strength of these C‐Ph composites were analyzed using thermogravimetry analysis and three‐point bending test, respectively. A significant improvement in the flexural strength and modulus of the reinforced C‐Ph composites was observed and also exhibited the higher thermal stability. The oxyacetylene flame test was conducted to measure the ablation behavior of these filler reinforced C‐Ph composites under a heat flux of 4.0 MW/m2 for 60 seconds. ZrO2/SiC0.5 reinforcement in the C‐Ph composite decreased the linear and mass ablation rates by 46% and 22%, respectively when compared with pure C‐Ph composite. The surface morphology analysis revealed that the burnt composite covered with the ZrC ceramic phase and SiO2 bubble‐like structure, which could have improved the ablation resistance of composites. These results were found well within the acceptable range when using the surface energy dispersive spectroscopy and X‐ray diffraction analysis.

Thermal stability and ablation resistance, and ablation mechanism of carbon–phenolic composites with different zirconium silicide particle loadings

ZrSi2 modified carbon–phenolic (C-Ph) composites are prepared using different weight loadings of zirconium silicide particle by compression moulding. The thermal stability and ablation resistance of composites are investigated by thermal gravimetric analysis (TGA) and oxyacetylene torch test. Moreover, the phase composition and microstructure of ablated surface are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and selected-area electron diffraction (SAED). The results show that introduced ZrSi2 particles result in an evident increase in the residual weights of C–Ph composites at high temperatures, and the enhancement in thermal stability under air atmosphere exhibits positive effects on improving the ablation resistance of C-Ph composites. The optimum ZrSi2 weight loading for the improvement of ablation resistance in C-Ph composites is 5wt%. The linear and mass ablation rates of composites after modifying with 5wt% ZrSi2 particles are reduced by 80.5% and 55.2%, respectively. This work provides an effective way to prominently improve the ablation performance of C–Ph composites, and it maybe become a backbone of thermal protection system in aerospace.

Shell on shell bonding of composite heat shield

Heat shield of a guided rocket experiences severe thermo-structural loads during flight especially during its re-entry phase. To meet the above requirement, Carbon Fibre Reinforced Plastic (CFRP) composite is the ideal choice of material which not only has high specific strength, stiffness, good thermal properties and light weight but also exhibits these properties at elevated temperatures. Heat shield is a two layered CFRP composite structure. Carbon Phenolic (CP) layer is an outer thermal member realized by tape lay-up method taking advantage of better ablation characteristics and Carbon Epoxy (CE) is an inner structural load bearing member fabricated by wet filament winding process to get tailor made structure. Each layer (CE & CP) is designed to meet its unique and distinct role. Realization of heat shield needs special attention as it is an assembly of multiple composite sections and also it is process intensive. The aim of this paper is to provide an insight into the established bonding methodology of two layered heat shield structure viz. selection of bonding material , qualification at coupon level both with metal and composite as substrate, tools and fixture, detailed established process and parameters, non-destructive testing of bonded structures, acceptance and qualification. It can be concluded that the structure bonded with the above established process methodology exhibits good bond quality post testing

Estimation of residual strain and stress in interply hybrid composite using fiber bragg grating sensor

Residual stress and strain buildup in the hybrid carbon/phenolic (CP) composite was estimated using embedded fiber Bragg grating (FBG) sensors. Two different carbon fabrics made from polyacrylonitrile (PAN) and rayon fibers were used. The partially delaminated hybrid composite was fabricated for the real-time and nondestructive estimation of the residual stress and strain during the cure process. The strain measured by FBG sensors embedded in the delaminated region was assumed to represent the thermal deformation of each reinforcing lamina. After the cure process was finished, PAN-based (PC) and rayon-based (RC) carbon laminae were under compression and tension, respectively, in in-plane direction because the strain of RC was 4.4 times lager than that of PC. The residual stresses of PC and RC laminae under the assumption of elasticity were −16.9 and 7.92 MPa, respectively. The experimental results showed good agreements with those by FEM analysis.

Kinetic constants of polymeric materials from thermogravimetric data

The thermal decomposition of polytetrafluoroethylene (TFE, Teflon), high and low density polyethylene (HDP and LDP), Delrin Acetal (DA), AVCO Phenolic Fiberglass (APFG), and carbon phenolic (CP), were studied by a thermogravimetric technique which utilized a constant heating rate. Loss in sample weight was recorded as a function of time or temperature from room temperature to approximately 700°. Reaction orders were established from logarithmic rate versus temperature plots. Arrhenius frequency factors and overall activation energies were determined from computerized integrations of the appropriate rate equations in which the results were treated on the basis of first-order reaction mechanisms for specific temperature regions. Zero-order mechanisms were estimated by the usual graphical methods.