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This article studies the effects of manufacturing defects of laminate composite materials on the first ply failure load and ultimate strength of the laminate, which are calculated using finite element modelling with Zinoviev’s damage model. The following types of defects are considered for cross-ply and quasi-isotropic layups: in-plane misalignement and out-of-plane waviness of fibres, misorientation of the layers and void content. The list of laminates studied in this article includes cross-ply and quasi-isotropic layups, loaded in tension and compression in 0°, 90°, 45° and 5° directions. The limits of the first ply failure load and strength degradation for a realistic range of the defect intensities are estimated.

Dynamic properties of the Shear Thickening Fluid (STF) are studied. Two series of tests by the Split Hopkinson Pressure Bar method were carried out to determine the dynamic bulk and shear properties of STF. The hypothesis about the possibility to describe STF behavior by a Newtonian fluid model in the characteristic range of strain rates is confirmed. A simplified mathematical model of the STF is then formulated for the use in computer simulation of ballistic impact tests of multilayered composite protective shells. The effectiveness of the STF impregnation for improvement of ballistic impact characteristics of Kevlar woven fabrics is confirmed. It is concluded that the role of the contact conditions between STF and Kevlar basis in the process of increasing the energy absorption capacity of Kevlar-STF barrier is significant, noting that the mechanism of contact interaction between STF and Kevlar basis can be described by viscous friction law, i.e., the STF behaves almost as a rigid body during the interactions with the solids, while it normally behaves as a fluid. It is also established that the STF impregnation of protective shells with titanium framework not only increases the absorption capacity of the whole package but also reduces the deflection of the metal base.

A new paradigm in continuous fiber-reinforced polymer fused filament fabrication based on a thermoset-thermoplastic bi-matrix material system is proposed and proved. This totally new 3-D printing concept has the potential to overcome the drawbacks and to combine the advantages of separate thermoset and thermoplastic-based, fused filament fabrication methods and to advance continuous fiber-reinforced polymer 3-D printing toward higher mechanical performances of 3-D printed parts. The novel bi-matrix 3-D printing method and preliminary results related to the 3-D printed composite microstructure and performances are reported.

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