A woven Five-Harness Satin (5HS) weave with AS4 carbon fibres, and unidirectional high strength IMS60 carbon fibres were used to manufacture hybrid laminates, using resin infusion, to assess their performance in low velocity impact tests. Load/energy-time curves and load-displacement curves were extracted from the experimental data, and non-destructive Cscanning was performed on all pre-and post-impacted specimens to quantify the extent of damage incurred. A finite element-based computational damage model was developed to predict the material response of these hybrid unidirectional/woven laminates. The intralaminar damage model formulation, by necessity, consists of two sub-models, a unidirectional constitutive model and a woven constitutive model. The built-in surface-based cohesive behaviour in Abaqus/Explicit was used to define the interlaminar damage model for capturing delamination. The reliability of this model was validated using in-house experimental data obtained from standard drop-weight impact tests. The simulated reactionforce and absorbed energy showed excellent agreement with experiment results. The post-impact delamination and permanent indentation deformation were also accurately captured. The accuracy of the damage model facilitated a quantitative comparison between the performance of a hybrid unidirectional/woven (U/W) laminates and a pure unidirectional (PU) carbon-fibre reinforced composite laminates of equivalent lay-up. The hybrid laminates were shown to yield better impact resistance.

The evaluation of Compression-After-Impact (CAI) strength is of great significance in the design of composite aerostructures. This paper presents a model for the numerical simulation of Compression-After-Impact (CAI) of hybrid unidirectional (UD)/woven carbon-fibre reinforced composite laminates. This three-dimensional damage model is based on Continuum Damage Mechanics (CDM) and Linear Elastic Fracture Mechanics (LEFM), and implemented as a user defined material subroutine (VUMAT) in Abaqus/Explicit. This model, which accounts for interlaminar and intralaminar damage, and load reversal, incorporates a non-linear shear profile to account for matrix plasticity. Two different composite laminate lay-ups with varying extent of initial impact damage were tested to validate the computational model and enable a quantitative study of the influence of using woven plies on the surfaces of a laminate. Woven surface plies are often used in composite aerostructures to mitigate damage during drilling and constrain the extent of damage during low velocity impact. Good correlation was obtained between physical testing and simulation results, which establishes the capability of this damage model in predicting the structural response of composite laminates. The fully validated model was used to compare the Compression-After-Impact (CAI) strength of an equivalent unidirectional (UD)-only carbon-fibre reinforced composite laminate. The results showed that the hybrid unidirectional (UD)/woven laminate had a marginally higher strength (+3.3%) than the equivalent unidirectional (UD)-only laminate.

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The present paper investigates the impact performance of woven-fabric carbon-fibre composites based upon both thermoplastic-and thermoset-matrix polymers under highvelocity impact loading by conducting gas-gun experiments at impact velocities of up to 100 m.s −1. The carbon-fibre reinforced-polymers (CFRPs) are impacted using soft-(i.e. gelatine) and hard-(i.e. aluminium-alloy) projectiles to simulate either a soft bird-strike or a hard foreign-body impact (e.g. runway debris), respectively, on typical composites employed in civil aircraft. The out-of-plane displacements of the impacted composite specimen are obtained by means of a three-dimensional Digital Image Correlation (DIC) system for the soft-projectile impact on the composites and the extent of damage is assessed both visually and by using portable C-scan equipment. The perforation resistance and energy absorbing capability of the composites are also studied by performing high-velocity impact experiments using the hard-projectile and the resulting extent and type of damage are identified. In addition, a Finite Element (FE) model is also developed to investigate the interaction between the projectile and the composite target.

A three-dimensional (3-D) Finite Element Analysis (FEA) model incorporating an elastic-plastic (EP) damage model, which was implemented as a user-defined material ('VUMAT') sub-routine in a FEA code ('Abaqus/Explicit'), is developed to simulate the impact response of carbon-fibre reinforcedplastic (CFRP) composites. The model predicts the load versus time and the load versus displacement responses of the composite during the impact event. Further, it predicts the extent, shape and direction of any intralaminar damage and interlaminar delaminations, i.e. interlaminar cracking, as a function of the depth through the thickness of the impacted CFRP test specimen, as well as the extent of permanent indention caused by the impactor striking the composite plate. To validate the model, experimental results are obtained from relatively low-velocity impact tests on CFRP plates employing either a matrix of a thermoplastic polymer, i.e. poly(ether-ether ketone), or a thermosetting epoxy polymer. The 3-D EP model that has been developed is shown to model successfully the experimentally-measured impact behaviour of the CFRP composites.