Compressive strength degradation in ZrB2-based ultra-high temperature ceramic composites

Keywords Composites; Borides; Carbides; Strength; Structural applications 1. Introduction

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Composites; Borides; Carbides; Strength; Structural applications

1. Introduction

The high melting point of refractory metal diborides coupled with their ability to form refractory oxide scales give these materials the capacity to withstand temperatures in the 1900–2500 °C range. These ultra-high temperature ceramics (UHTCs) were developed in the 1960s. [1] Fenter [2] provided a comprehensive review of the work accomplished in the 1960s and early 1970s. These materials are almost never used in pure form. Instead, additions of silicon carbide are used to enhance oxidation resistance and limit diboride grain growth. [3], [4], [5] and [6] Carbon is also sometimes used as an additive to enhance thermal stress resistance. [7], [8] and [9] These materials offer a good combination of properties that make them candidates for airframe leading edges on sharp bodied re-entry vehicles. [10] UHTCs have potential to perform well in such applications’ environment, i.e. air at low pressure. Some interest has also been shown in these materials for single use propulsion applications.[11]

Major improvements in the manufacturing and characterization of ZrB2 materials and composites have been put forward in recent years, and now several important aspects of their properties and processing are well understood. [4], [12], [13], [14], [15], [16], [17], [18], [19], [20] and [21] However, the study of high temperature properties has been mostly limited to oxidation behavior, an area which is also well understood. [8], [21], [22], [23], [24], [25], [26], [27] and [28] Very few studies of high temperature mechanical properties exist. [7], [11] and [29]

In this work, we investigated the mechanical behavior of ZrB2–SiC composites, with and without added C and SCS-9a fibers. Samples were studied in compression at room temperature, 1400, and 1550 °C, in atmospheric air. The degradation of the mechanical properties as a result of atmospheric air exposure at high temperatures were also studied as a function of exposure time.

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