Understanding the Role of Carbon Fiber Skeletons in Silicone Rubber-Based Ablative Composites

At present, silicone rubber-based ablative composites are usually enhanced by carbon fibers (CFs) to protect the case of solid rocket motors (SRMs). However, the effect of the CFs’ length on the microstructure and ablation properties of the silicone rubber-based ablative composites has been ignored. In this work, different lengths of CFs were introduced into silicone rubber-based ablative composites to explore the effect of fiber length, and ceramic layers of various morphologies were constructed after ablation. It was found that a complete and continuous skeleton in ceramic layers was formed by CFs over 3 mm in length. In addition, the oxyacetylene ablation results showed that the linear ablation rate declined from 0.233 to 0.089 mm/s, and the maximum back-face temperature decreased from 117.7 to 107.9 °C as the length of the CFs increased from 0.5 to 3 mm. This can be attributed to the fact that successive skeletons concatenated and consolidated the ceramic fillers as well as residues to form an integrated, robust, and dense ceramic layer.

Changing the Sizes of Details Made of Aluminum Alloys during Microarc Oxidation Process

It is shown that microarc oxidation (MAO) makes it possible to increase the size of aluminum alloy details by forming dense ceramic coatings (MAO-coatings) on them. Found that MAO-process a duration of 50...80 minutes in a liquid solution according to conventional technology allows you to increase the size of the details made of deformable alloy AMg3 and D16 by 78...80 % of the thickness formed on them MAO-coating and MAO-process in solution of corundum particles opens the possibility of increasing the same details by 98...100 % of the thickness formed on them more thick MAO coating. Revealed that increasing solution temperature from 15 to 45 оС leads to a reduction in the thickness of MAO coating and an even more significant reduction in growth dimensions, as well as to reduce the quality of their surfaces. It is shown that the removal of the outer layers of MAO coatings to a thickness of 20 ... 25 μm by grinding contributes to a significant reduction in the roughness of the surfaces of details. It is confirmed that MAO coatings obtained in liquid solution and in solution with corundum particles have a similar mainly polycrystalline structure, but MAO coatings obtained in solution with corundum particles differ in greater thickness and higher corundum content (α-Al2O3). It is established that the outer layers of MAO coatings are characterized by a relatively low content of modifications of crystalline aluminum oxide, so after their removal, the strength properties of the surfaces of details also improve. The principal possibility of increasing the size of details made of deformable aluminum alloys by 150 μm with ensuring high quality of their surfaces is proved.

The effect of the dispersed composition of SiC on the physical and mechanical properties of reactionsintered silicon carbide

We obtain dense ceramic materials of silicon carbide by reaction sintering, with high mechanical properties. The effect of different dispersed composition of silicon carbide powders on the microstructure, grain size after sintering, as well as physical and mechanical properties is shown.