Low velocity impact behaviour of bi-layered laminates of acrylic and polycarbonate was investigated using a combination of drop tower impact experiments and explicit finite element analysis in LS-DYNA. Material characterisation tests were conducted in tension and in compression to obtain material properties for input to the material model in the numerical analysis. Quasistatic plate bending tests were conducted at different loading rates to compare the quasistatic response of the materials to the impact behaviour. Impact tests on circular plates of monolithic acrylic and polycarbonate were carried out using an instrumented drop weight impact tester. The impact force histories were recorded and a multiparameter approach was used to determine critical energy. Acrylic exhibited radial cracking, spalling and pene- tration while polycarbonate underwent large deformation and failed by dishing and plugging. The damage caused by impact in the bilayered laminate included partial or full delamination at the interface and radial cracks in the acrylic layer. The low velocity impact responses were simulated using 8-noded solid elements in LS- DYNA. A node-splitting technique based on maximum tensile stress failure criterion and an erosion approach based on maximum principal stress criteria was used to model the failure of acrylic. A material model that takes into account the asym- metric behaviour in tension and compression was investigated. The delamination between the acrylic and polycarbonate plate was modelled by a tiebreak contact with a shear strength based failure. The results of the finite element simulations are in good agreement with the experimental data.

Hybrid polymer laminates of polycarbonate and PMMA have generated considerable interest among researchers as an alternative to traditional glass armours because of their potential for reduced cost and weight. Generally, the development of ballistic armour is carried out experimentally which is an expensive task in terms of time and cost. Numerical simulation provides a much greater facility to understand the phenomenon of ballistic impact and the effects of various parameters on the response to such impact. In addition it provides an easy means of comparing the impact performance of different materials as well as combination of materials forming hybrid laminates. The aim of this research was to develop a numerical modelling capability to simulate the ballistic response of hybrid polymer laminates, specifically polycarbonate and PMMA, using a commercially available finite element code LS-DYNA. The challenge was to work within the limitations of the material models and the failure algorithms available within LS-DYNA, and still try to reproduce the behaviour observed experimentally by previous researchers, initially on monolithic plates of polycarbonate and PMMA and then on hybrid laminates. The first part of the study focuses on a detailed literature survey on mechanical and dynamic characterisation of polycarbonate and PMMA as well as experimental and numerical studies previously conducted on ballistic behaviour of these materials as well as their combinations. The material properties of the polymers compiled from this literature survey were used as input for the selected LS-DYNA material model. Impact simulations were carried on monolithic and laminated media of polycarbonate and PMMA and where possible these were compared to experimental results. It was observed that the results agreed with the experimental data qualitatively. Quantitatively the results showed some discrepancies which were attributed to the limitations faced in simulating the exact test conditions numerically. Numerical simulations were carried out to study the effects of variations in laminate thickness and plate support diameters as well as to examine the influence of the bond between the layers. Finally the impact response of four different combinations of polycarbonate and PMMA are compared to each other for different laminate thicknesses.