No abstract

No abstract

In this study, the mechanical behavior and porosity of a T700/epoxy composite material under high temperature conditions were investigated. The 0°/90° compression, tensile, interlaminar, and in-plane shear experiments of composite samples were performed at temperatures from 23°C to 170°C. The true strain–stress curves of composite samples were obtained. The cross section and fracture regions of the tested samples were analyzed by Scanning Electron Microscopy and X-ray tomography to understand the microstructure property relationships. It was observed that the mechanical performance of carbon fiber/epoxy composites generally decreased with increasing temperature. By comparing the fracture morphology, it was found that the fracture mechanism of the composites changed from interfacial debonding to matrix failure with increasing temperature. Three-dimensional visualization of porosities after mechanical experiments under high temperature conditions was reconstituted from X-ray tomography scan images. The results showed that the porosity fraction of the tested samples under high temperature conditions was generally higher than that under lower temperature conditions. Moreover, for the 90° tensile test, the diameter of the pores was mainly located at 4–12 μm and was almost constant along different distances to the failure edge. Meanwhile, compared with the tensile test, larger size of pores in samples of 90° compression tests were observed.

The damage and ignition response of a novel propellant is investigated using a modified split Hopkinson pressure bar (SHPB). The mechanical response of the propellant exhibits strong strain rate dependency following a power law. The whole process from mechanical damage to onset of ignition, deflagration and potential deflagration to detonation transition (DDT) under different strain rates (1000–5000 s−1) is captured via high‐speed photography and digital image correlation (DIC). To clarify the onset and extent of the resulting reaction in terms of the mechanical damage caused by impact, meso‐scale analysis is used to evaluate the propellant before and after dynamic impact loading. The ignition response under impact loading is mainly caused by shear flow, and ignition after multiple impacts due to the reflection of stress waves. Dense debris clouds produced by the first impact are observed in the case of a strain rate of 5000 s−1 leading to DDT when the second impact initiated ignition.