Micro-mechanical finite element analysis of Z-pins under mixed-mode loading

Published on Nov 1, 2015in Composites Part A-applied Science and Manufacturing7.664
· DOI :10.1016/J.COMPOSITESA.2015.07.006
Bing Zhang10
Estimated H-index: 10
 (UoB: University of Bristol), Giuliano Allegri21
Estimated H-index: 21
 (ICL: Imperial College London)+ 1 AuthorsStephen R. Hallett53
Estimated H-index: 53
 (UoB: University of Bristol)
Sources
Abstract
This paper presents a three-dimensional micro-mechanical finite element (FE) modelling strategy for predicting the mixed-mode response of single Z-pins inserted in a composite laminate. The modelling approach is based upon a versatile ply-level mesh, which takes into account the significant micro- mechanical features of Z-pinned laminates. The effect of post-cure cool down is also considered in the approach. The Z-pin/laminate interface is modelled by cohesive elements and frictional contact. The progressive failure of the Z-pin is simulated considering shear-driven internal splitting, accounted for using cohesive elements, and tensile fibre failure, modelled using the Weibull's criterion. The simulation strategy is calibrated and validated via experimental tests performed on single carbon/BMI Z-pins inserted in quasi-isotropic laminate. The effects of the bonding and friction at the Z-pin/laminate interface and the consequences of the internal Z-pin splitting are discussed in detail. The primary aim is to develop a robust numerical tool, as well as guidelines for designing Z-pins with optimal bridging behaviour. .
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References33
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Abstract A new micro-mechanical model is proposed for describing the bridging actions exerted by through-thickness reinforcement on delaminations in prepreg based composite materials, subjected to a mixed-mode (I–II) loading regime. The model applies to micro-fasteners in the form of brittle fibrous rods (Z-pins) inserted in the through-thickness direction of composite laminates. These are described as Euler–Bernoulli beams inserted in an elastic foundation that represents the embedding composit...
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Abstract This paper presents an experimental characterisation of the mechanical performance and behaviour of through-thickness reinforced composite laminates. To achieve this, composite blocks with individual reinforcing pins were manufactured, quality assessed and tested. Individual specimens were inspected using X-ray Computed Tomography and only the specimens with acceptable quality pin insertions were tested experimentally under a range of mode mixities. Two stacking sequences, uni-direction...
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In the framework of the EU program ALCAS (advanced low-cost aircraft structure), a new Z-pinning technique was developed by EADS Innovation Works. It was used to manufacture low-cost Z-pinned junction demonstrators (L and T shaped specimens) typical of aeronautical structures. In order to understand load transfer mechanisms in this kind of assembly, a multi-level analysis was performed. Firstly, tension and shear pin behaviour was investigated as well as pin pull-out from net resin. It was demon...
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Dec 1, 2011·Composites Part A-applied Science and Manufacturing7.66
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Abstract In the framework of the E-U program ALCAS (Advanced Low-Cost Aircraft Structure), a new Z-pinning technique was developed by EADS Innovation Works. This technology was used to manufacture low-cost Z-pinned junction demonstrators (L and T shaped specimens) typical of aeronautical structures. In order to understand load transfer mechanisms in this kind of assembly, a multi-level analysis was performed. In the first part of this study, tension and shear pin behaviour was investigated as we...
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A numerical model for analyzing the bridging mechanisms of Z-pining in composite laminates is presented. Main failure modes of the Z-pin are: debonding between the Z-pin and matrix, split and rupture of the Z-pin material; these have been taken into account here. The cohesive zone model was utilized to simulate splitting and rupturing within the Z-pin. The interfacial contact between the Z-pin and matrix was assumed to be initially bonded, followed by debonding and frictional sliding. The presen...
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