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In this article, the open‐hole tensile behaviour of carbon fibre reinforced aluminium laminates (CARALL) were investigated experimentally and numerically. Two specimens with different fibre orientations ([0°/90°/0°] and [45°/0°/−45°]), consisting of T700 carbon fibre/epoxy prepreg and 2024‐T3 aluminium with a 3/2 configuration, were manufactured by the autoclave process. Damage initiation and progression were considered in modelling the CFRP layers and interface bonding layers. Isotropic hardening behaviour was defined for aluminium layers. A major contribution of this study was to reveal the failure mechanisms and failure sequences of notched CARALL with different fibre orientations by numerical method. Damage evolution processes of the two specimens were compared. Effects of hole sizes and laminate configurations (stacking sequences & stacking structures) on both the specimens were further evaluated based on simulation. Point stress failure criterion and Wu's modified point stress failure criterion were applied in comparison with the numerical method as well. POLYM. COMPOS., 39:4123–4138, 2018. © 2017 Society of Plastics Engineers

In broadband satellite communication systems, beam hopping (BH) is more and more welcome to compensate the low-power-efficiency wide beam and the lowspectrum-efficiency multiple spot beams simultaneously. As a flexible coverage method, BH demands efficient hopping strategy to reach the desired quality of service (QoS). In this paper, we consider the QoS equilibrium, in particular the delay fairness, among different cells illuminated by one hopping beam through designing the hopping strategy on the condition of capacity satisfaction. Due to the physical limitation that hopping speed is much slower than packet arrival speed, the ideal first-come-first-serve packet scheduling is not realizable, which compels us to pursuit the optimal slot scheduling instead. In this paper, we consider a long-term delay fairness problem by perperiod slot allocation for BH, using instantaneous and statistical information. To deal with the complex stochastic programming problem, we introduce the time-sharing principle to uncouple the variables and adopt stochastic gradient theory to deduce the suboptimal close-form solution. Our contributions are in three folds: firstly, it is the first time to consider the delay fairness not the traditional capacity fairness for BH; secondly, a general per-period decision scheme is proposed for the unique slot allocation in the perspective of queuing; thirdly, a suboptimal closeform solution for the per-period slot allocation is obtained, which could also cope with burst traffic cases. In simulation, we verify our method's advantage in terms of delay fairness comparing with the existing similar works.

Compared with the resin-based composite laminates, fiber metal laminates (FMLs) have superior impact resistance. In this study, investigations were made to reveal the effects of stacking sequence on the low-velocity failure mechanisms and energy dissipation characteristics of carbon fiber reinforced plastics (CFRP)/ Al hybrid laminates with same areal density. Experiments were carried out to characterize the typical mechanical responses. Failure morphologies were evaluated by X-ray computed tomography scanning techniques. Then numerical simulations based on three-dimensional progressive damage analysis were applied to reveal the dynamic evolution process and energy dissipation characteristics. Results indicated that plastic deformation of aluminum layers acted as the dominant factor in energy dissipation. Stacking aluminum layers on the exterior surface could increase the absorbed impact energy and reduce the fracture behavior of the component layers. The specimens with more CFRP layers stacked on the surface exhibited more severe fracture behavior of component layers and larger delamination areas, thus promoting the energy dissipated by CFRP cracking and delamination. This work intended to provide practical guidance for the structural design of fiber reinforced polymer/metal hybrid protective structures.

This paper investigated the in-plane bending behaviour of carbon fibre-reinforced aluminium laminates (CARALL). The flexural progressive damage and failure mechanisms were analysed numerically and experimentally. Four types of CARALL specimens with a 3/2 configuration were prepared via hot-pressing using different aluminium alloy materials (2024-T3, 7075-T6 aluminium alloy) and fibre orientations ([0 /90 /0 ] 3 , [45 /0 /À45 ] 3 ). The three-point bending tests were conducted under static loading. It was found that the primary damage modes were aluminium layer yielding in the mid-span and delamination between the aluminium and carbon fibre-reinforced polymer (CFRP) layers. A user-defined FORTRAN subroutine VUMAT based on ABAQUS was used to simulate the failure of the CFRP, a cohesive zone model was used to predict the inter-laminar failure, and a von Mises plastic model was used to define the isotropic hardening behaviour of the aluminium layers. The predicted results agreed well with the experimental ones. Two convenient calculation methods based on the elasticity mechanics and material mechanics were derived. And the non-linear behaviour of aluminium was considered in the elasticity mechanics method. The theoretical results matched closely with the experimental findings during the linear elastic deformation process.