Research On Ballistics Resistance And Failure Mechanism Of Fiber-Reinforced Laminate

As fiber-reinforced laminate is used extensively in defense engineering, study of the mechanical response, ballistic performance and failure mechanism of laminate under impact loading are becoming more and more interested by researchers. Because of the anisotropic behavior, multi-phase structure, varied damage modes and failure patterns, research on fiber-reinforced laminate is still quite limited compared with the conventional metals and so that it needs to be speed up. In this paper, Systemic studies including experiments, engineering analyses and numerical simulations on the penetration and perforation of laminate at different loading conditions are conducted.Dynamic and static mechanical behavior of two kinds of fiber-reinforced laminates--angle-plied and woven Kevlar/epoxy laminates are studied by a series MTS and SHPB tests. On the basis of tested stress-strain curves of laminated Kevlar, an empirical constitutive equation considering strain-rate hardening and damage softening is proposed and discussed. The key point of the equation is that a factor ,that is stiffness-strengthened factor is suggested to describe the effect of fiber lay-up on the mechanical properties of the laminates.Penetration and perforation tests of Kevlar laminates are carried out by flat-ended or conical-nosed indenters/projectiles in quasi-static or ballistic impact loading. Based on the test results, the effects of projectile shapes, plate thickness and types of fiber lay-up on penetration resistances and failure modes of laminated Kevlar are investigated. Experimental results indicate that woven laminate absorbs much more energy than angle-plied laminates during quasi-static penetration. However, different from quasi-static case, ballistic resistance of the two kinds of laminates is mainly affected by target thickness. Angle-plied laminate is demonstrated a comparative ballistic resistance to woven laminate in the case of thin thickness. With the increase of target thickness, angle-plied laminate exhibits a little stronger resistance than woven laminate.Engineering analytical models for laminates penetrated by flat-ended indenters /projectiles at quasi-static or ballistic loading are investigated in the thesis. The model assumes that the total deformation of laminate in quasi-static penetration can be decomposed of global and local parts and correspondingly, different failure criteria must be used for different failure modes. Based on these assumptions, an analytical...