PSI - Issue 14

Hemant Chouhan et al. / Procedia Structural Integrity 14 (2019) 830–838 Author name / Structural Integrity Procedia 00 (2018) 000–000

837

8

Fig. 4. Surface fit plot of the SHPB results of UHMWPE-SR composite for (a) dry and (b) wet specimen. Similarities can be noted between Eq. (6) and the models discussed earlier. To begin with, the first term may be correlated with Eq. (4) describing the elastic behavior of the composite which may not necessarily be linear in nature. The second term represents rate dependent material behaviour which arises as a function of viscous behaviour of polymer matrix and polymeric fibers due to adiabatic heating of composite specimen, owing to low time of loading. On achieving the equilibrium (stable incident energy) the simultaneous effect of both the elastic and plastic behaviour is represented by the third term in Eq. (6). This term strongly bears a resemblance to the Cowper– Symonds plasticity model (Eq. (5)), which is frequently used to describe the yielding behaviour of metals and composites (Peroni et al. 2012). 5. Conclusions In this study, the effect of moisture ingestion on compressive high strain rate behavior of UHMWPE-SR composite is estimated using SHPB. From the experimental results following inferences are drawn: i.) In general, the compressive properties enhances with increasing strain rate of loading for both the dry and wet UHMWPE-SR composite. ii.) The rate-dependent behavior of dry composite reveals nearly constant peak stress with growing total strain. This type of material behavior is essential for trapping a projectile inside a composite laminate. iii.) Significant moisture ingestion by the composite specimen resulted in drastic reduction of the mechanical properties. The peak stress of the wet specimen was limited below half the stress attained by the dry composite. iv.) The effect of time elapsed between the specimen removal from the water bath to high strain rate loading was noted to be significant on the composite properties. v.) The phenomenological model derived from the surface fitting of experimental observations was found to accurately predict the rate-dependent behavior of UHMWPE-SR composite under high strain rate loading. Acknowledgments The authors are thankful to JATC-DRDO (ABSSP-1) for the grant of this research project and Honeywell Inc. USA for the material support. References Allazadeh, M. R., Itani, M. K., Wosu, S. N., 2012. Compression of the Material Characteristics of Steel, Aluminum, Wood and Woven Graphite Epoxy Composites in Response to High Strain Rate Load. Advances in Materials Science and Applications 1(1), 13–30. Asija, N., Chouhan, H., Gebremeskel, S. A., Singh, R. K., Bhatnagar, N., 2017. High Strain Rate Behavior of STF-Treated UHMWPE Composites. Int Jr of Impact Engineering 110, 359–64.