Abstract
Abstract Dynamic compressive tests of 3D braided composites with different braiding angle were carried out in the longitudinal, transverse and thickness directions respectively using the Split Hopkinson pressure bar (SHPB). The results show that the compressive properties present obvious strain rate strengthening effects in all directions. The 20° and 45° braided composite are most sensitive to strain rates in the longitudinal direction. The composites present the features of brittle failure at high strain rates, especially in the longitudinal direction. The composites with larger braiding angle have weaker mechanical properties in the longitudinal and transverse directions but stronger mechanical properties in the through-thickness direction. The braid angle has the greatest impact on the longitudinal mechanical properties. The compressive stress-strain curves in the thickness direction were similar to the hysteresis curve for both the 30° and 45° braided composites. The compressive failure modes vary with the loading directions and strain rate.
Highlights
Three-dimensional (3D) braided composites is an promising composite material (Mouritz et al, 1999), which have been widely employed in aviation applications due to its high interlaminar shear strength and excellent impact resistance (Kamiya et al.,2000; Bilisik, 2013)
The quasi-static and dynamic compression tests were conducted in different directions on the three-dimensional four-step braided composites with different braiding angles
The main conclusions are as follows: (1) For 3D braided composites, the compressive ultimate strength increases with the strain rate in the longitudinal, transverse and thickness directions, showing obvious strain rate strengthening effects in all directions
Summary
Three-dimensional (3D) braided composites is an promising composite material (Mouritz et al, 1999), which have been widely employed in aviation applications due to its high interlaminar shear strength and excellent impact resistance (Kamiya et al.,2000; Bilisik, 2013). To study the impact resistance and failure modes of 3D braided composites, ballistic impact tests were generally conducted by researchers. Sun and Gu (2007a, 2007b) studied out-plane and in-plane compressive and uniaxial tensile behavior of 4-step 3D braided composites at high strain rates through experiments. The mechanical properties of 3D braided composite materials are strain rate sensitive Both the failure stress and compressive stiffness increase with strain rate. The 3D 5-directional braided composites were tested to obtain its uniaxial compressive behavior at strain rates ranging from 350 s-1 to 1600 s-1 (Wang et al, 2010). The effect of loading direction and braiding angle on the dynamic compressive behaviors of 4-step 3D braided carbon fiber/epoxy composites at strain rates ranging from 800 s-1 to 2000 s-1 was studied experimentally through SHPB apparatus. The compressive stressstrain curves, compressive modulus, failure stress/strain and the energy absorption of 3D braided composites at the longitudinal, transverse and thickness directions were obtained and compared
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