Dynamic Response of Symmetric and Asymmetric E-Glass / Epoxy Laminates at High Strain Rates

Abstract

The mechanical properties of E-glass/epoxy composite at high strain rates are important in evaluating this kind of composite under dynamic and impulsive loading. The in-plane and out-of-plane compressive properties at strain rates from 300 to 2500 s-1 were tested with split Hopkinson pressure bar. Samples were tested in the thickness as well as in-plane direction for seven fibre orientations: 0°, 20°, 30°, 45°, 60°, 70° and 90°. The kinetics of damage and the failure modes were identified using a high-speed photography, infrared camera, optical techniques and a scanning electron microscope. Results of the study were analyzed in terms of maximum stress, Strain at maximum stress, failure modes, damage history and fibres orientation effects. From the experimental data, the stress-strain curves, compressive stiffness, and compressive strain of the composite are rate-sensitive in in-plane and out-of-plane compressive directions. The failure and damage mechanisms are implicitly related to the rise in temperature during static and dynamic compression.

An investigation of in-plane dynamic behavior of adhesively-bonded composite joints under dynamic compression at high strain rate

“…It can be seen that the respective incident, reflected and transmitted wave heights depend significantly on the striker bar velocity. As expected [3][4][5][6][7][8][9][10][11][12], the second peak of the reflected pulse and the short duration of the transmitted pulse, show the presence of macroscopic damage in the adhesively bonded joints when it is subjected to the in-plane compressive loads. Thus, it can be concluded that the tests at 1 bar correspond to the non damaged case during which the pressure wave is reflected back through the assembled specimen with a fairly elastic response.…”

“…However, for each strain rate, a small difference between the incident and the transmitted loads is marked. This can not only be attributed to the self-installation of the assembled sample between the bars but also to the parallelism of the samples facets in contact with the bars which is not 100% guaranteed, as shown in previous works [3][4][5][6][7][8][9][10][11][12]. As the case of strain rate, one can see that the incident load and velocity profiles reveal clearly the appearance of a second peak which characterizes the presence of macroscopic damage for the damaged tests, as previously mentioned.…”

“…2). Details of the SHPB experimental protocol are mentioned in [3][4][5][6][7][8][9][10][11][12].The SHPB apparatus basically consists of an incident bar, a transmitted bar and sticker bar. Both the incident and transmitted bars have a diameter of 20 mm and a length of 1.9850 m. A striker bar of 20 mm diameter and a length of 2 m is used to generate an incident stress via impact with the incident bar.…”

“…However, the increase in impact pressure (3 and 4 bar) shows that the strain rate increases before the decrease in the second step. The appearance of a second peak is the principal characteristic of these curves detecting the presence of the onset of macroscopic damage as demonstrated by Tarfaoui et al [3][4][5][6][7][8][9][10][11][12].…”

“…Thus, it is significant to achieve an accurate description of damage under dynamic loading and effect of strain rate on the behavior of these materials for safety and design considerations. The split Hopkinson bar (SHPB) has been widely used to determine the dynamic properties of materials at high strain rates [3][4][5][6][7][8][9][10][11][12]. Significant efforts have been made to investigate the effect of high strain rate on the dynamic behaviour of polymers adhesives and composites laminates using the Split Hopkinson bar under various loading conditions [13][14][15][16].…”