Low-impulse blast behaviour of fibre-metal laminates

This paper presents three dimensional (3D) finite element (FE) models of the low-impulse localised blast loading response of fibre-metal laminates (FMLs) based on an 2024-O aluminium alloy and a woven glass-fibre/polypropylene composite (GFPP). A vectorized user material subroutine (VUMAT) is developed to define the mechanical constitutive behaviour and Hashin’s 3D failure criteria incorporating strain-rate effects in the GFPP. In order to apply localised blast loading, a user subroutine VDLOAD is used to model the pressure distribution over the exposed area of the plate. These subroutines are implemented into the commercial finite element code ABAQUS/Explicit to model the deformation and failure mechanisms in FMLs. The FE models consider FMLs based on various stacking configurations. Both the transient and permanent displacements of the laminates are investigated. Good correlation is obtained between the measured experimental and numerical displacements, the panel deformations and failure modes. By using the validated models, parametric studies can be carried out to optimise the blast resistance of FMLs based on a range of stacking sequences and layer thicknesses

Modelling of the low-impulse blast behaviour of fibre–metal laminates based on different aluminium alloys

A parametric study has been undertaken in order to investigate the influence of the properties of the aluminium alloy on the blast response of fibre–metal laminates (FMLs). The finite element (FE) models have been developed and validated using experimental data from tests on FMLs based on a 2024-O aluminium alloy and a woven glass–fibre/polypropylene composite (GFPP). A vectorized user material subroutine (VUMAT) was employed to define Hashin’s 3D rate-dependant damage constitutive model of the GFPP. Using the validated models, a parametric study has been carried out to investigate the blast resistance of FML panels based on the four aluminium alloys, namely 2024-O, 2024-T3, 6061-T6 and 7075-T6. It has been shown that there is an approximation linear relationship between the dimensionless back face displacement and the dimensionless impulse for all aluminium alloys investigated here. It has also shown that the residual displacement of back surface of the FML panels and the internal debonding are dependent on the yield strength of the aluminium alloy

The influence of composite core thickness on the perforation resistance of titanium-based FMLs

Fibre metal laminates (FMLs) have been widely used as structural materials in aerospace applications due to their superior properties compared to traditional fibre reinforced composites. FMLs are hybrid materials consisting of alternating sheets of metal and plain composite. The aim of this study is to investigate the impact response of FMLs that have potential applications in the next generation of aircraft. Here, the influence of the thickness of the composite core in a 2/1 (metal/composite/metal) titanium alloy-based fiber metal laminate were investigated under low velocity impact conditions. It is shown that increasing the thickness of the composite core resulting in higher values of impact force and absorbed energy. The FMLs offered a much higher specific perforation energy than that offered by the plain composite for a given thickness of composite core.Explicit finite element (FE) models were developed to predict the response of the laminates under low velocity impact loading, which were then validated by comparing the numerical predictions with the corresponding experimental results. The resulting FE predictions showed good agreement with the experimental data in terms of the load-displacement trace, peak impact force, absorbed energy and perforation mechanisms

Dynamic response of aluminium matrix syntactic foams subjected to high strain-rate loadings

This paper presents experimental work to characterise the dynamic behaviour of aluminium matrix syntactic foams subjected to compression, Split Hopkinson Pressure Bar and terminal ballistic impact tests as well as blast loading. Numerical models have also been developed to simulate the dynamic response of the composite foams. The effect of strain-rate on their compressive crush behaviour has been investigated, given that the rate-dependent characteristics of these materials are required for designing dynamically loaded structures. Characterisation of the behaviour of the foam under high strain-rate loadings and the identification of the underlying failure mechanisms were also undertaken to evaluate their effective mechanical performance. The results show that the aluminium syntactic foam is sensitive to strain-rate in terms of initial stiffness, peak stress and plateau stress and show a pronounced high-rate dependence at a strain rate above 1000 s-1. The concrete damage plasticity model with rate-dependent features were used to simulate the dynamic behaviour of the foams, with the failure modes being captured. The model was verified and validated against the experimental results, and predictions were made for the normal and oblique ballistic impact response. Overall, the level of agreement between the numerical simulations and the experimental results is encouraging

Dynamic monitoring research on displacement of rock mass in coal seam floor on the 1604 workface in NanTun coalmine, Shandong Province, China

AbstractIn order to understand the displacement regular of rock mass in coal seam floor, displacement monitoring sensors were arranged in underground boreholes and realized the dynamic monitoring displacement of rock mass. First, the geological and the hydrogeological condition of the 1604 workface and NanTun coalmine were analyzed. Second, boreholes was constructed in roadway on the 1604 workface, displacement monitoring sensors were arranged in boreholes in different depth, when the distance of mining position and borehole was 110 m, the displacement monitoring sensor started monitoring, which the different depth displacement data were collected. Last, through comparing displacement data in different depth, the paper point out as the development of mining the influence degree of the displacement of rock mass in coal seam floor can be divided into initial influence stage, obvious influence stage and significant influence stage. Workface mining caused the depth of the rock mass displacement variation from 11.95 to 13.94 m below coal seam. The result will guide the coalmine prevention and control of water inrush from coal seam floor