716 research outputs found
Open hole compressive strength of composite laminates and sandwich panels: Comparison between Budiansky-Fleck-Soutis model and experiments
No full textIn this study, the compressive behaviour of carbon fibre reinforced plastic quasi-isotropic laminates and sandwich panels with carbon fibre reinforced plastic face sheets and syntactic foam core has been investigated. Experimentally determined open hole strengths have been compared with theoretical predictions obtained by applying a linear cohesive zone model. The unnotched compressive strength has been experimentally determined, and the in-plane fracture toughness has been analytically predicted as input parameters of the model. Buckling phenomena occurred on some specimens, and they have been taken into account. Evaluation of macroscopic failure modes in compression tests on unnotched specimens led to a better understanding on the advantages of the analytical model and on the possibility of applying the model to sandwich structures. The experimental results were in good agreement with the analytical prediction by the Budiansky-Soutis-Fleck cohesive zone model, and the difference between theoretical and experimental open hole strengths of Syncore sandwich panels was <9%
Introduction
No full textThe growing use of composite material has arisen from their high specific strength and stiffness, when compared to the more conventional materials, and the ability to tailor their structure to produce more aerodynamically efficient structural configurations. In this introductory chapter, it is argued that fibre reinforced polymers, especially carbon fibre reinforced plastics (CFRP), can and will in the near future contribute more than 50% of the structural mass of an aircraft. Of course, affordability is the key to survival in aerospace, whether civil or military, and therefore effort should be devoted to low cost manufacturing methods in addition to analysis and computational simulation of the manufacturing and assembly process. The simulation of the structural performance should not be neglected, since they are intimately connected
Aerospace engineering requirements in building with composites
No full textThe growing use of composite material has arisen from their high specific strength and stiffness when compared to the more conventional materials, and the ability to tailor their structure to produce aerodynamically more efficient structural configurations. In this introductory chapter, it is argued that fiber-reinforced polymers, especially carbon fiber-reinforced plastics can and will, in the near future, contribute more than 50% of the structural mass of an aircraft. Of course, affordability is the key to survival in aerospace, whether civil or military and therefore, effort should be devoted to low-cost manufacturing methods in addition to analysis and computational simulation of the manufacturing and assembly process. The simulation of the structural performance should not be neglected since they are intimately connected. Virtual reality models in engineering prior to manufacturing to identify potential problems will make Industry 4.0 and the smart factory for composites a reality. Industry 4.0 focuses on data-driven manufacturing, where in the future, billions of machines, systems, and sensors will communicate with each other and share information, physical systems connected to digital twins, the Industrial Internet of Things (IIoT). This will not only enable companies to make design and production significantly more efficient, but it will also give them greater flexibility when it comes to tailoring production to meet market requirements
Open hole compressive strength of composite laminates and sandwich panles: a comparison between the Budiansky-Fleck-Soutis model and experiments
No full textCompressive response of notched, woven fabric, face sheet honeycomb sandwich panels
No full textCentre notched honeycomb sandwich panels with woven carbon-epoxy face sheets and Nomex™ cores, tested uniaxially in compression, have been analysed to estimate their strength and damage tolerance. A plain weave T-300 carbon fibre fabric was used for the face sheets in two stacking sequences:[45/0/90] and [0/90]. Observations of macroscopic damage behaviour were different in the two layups. Linear damage zones (LDZs), consisting of fibre microbuckles and extensive delamination, were typically observed in the [0/90] material. The [45/0/90] material exhibited a delamination/bulge zone (DBZ), which consisted of an out of plane curved deformation of the outer 45° ply accompanied by a delamination from the interior 0° plies. Modelling of these failure modes and comparison with experimental data showed that the only mode representative of damage tolerant behaviour is LDZ formation and propagation for both material systems, and that the delamination/bulge behaviour is a secondary phenomenon. A linear softening cohesive zone model predicts the notched compressive strength reasonably well
Strength prediction of patch-repaired CFRP laminates loaded in compression
No full textThe repair of a composite structure with a composite patch may use mechanical fastening, which often introduces undesirable stress concentrations or adhesive bonding, external or flush patches. In this paper the compressive behaviour of bonded external patch repairs is examined; the compressive loading mode is more severe than the tensile mode owing to the instability of delaminated plies, instability of the patch and skin strength reductions occurring under elevated temperatures and absorbed moisture conditions. By using a non-linear shear-lag analysis [Soutis C, Hu FZ. Design and performance of bonded patch repairs of composite structures. Proc Instn Mech Engrs 1997;211(G):1–9], design guidelines are produced for the selection of patch size, shape and membrane stiffness. A three-dimensional finite-element analysis is then performed to determine the stress field in the optimum repaired configuration and is used with a recently developed cohesive zone model [Soutis C, Fleck NA. Static compression failure of carbon fibre T88/924C composite plate with a single hole. J Compos Mater 1991;24(5):536–58; Soutis C. Damage tolerance of open-hole CFRP laminates loaded in compression. Composites Engineering 1994;4(3):317–27] to estimate the compressive failure load of the repaired laminate. The predicted strength is within 10% of the experimental data
Open hole compressive strength of composite laminates and sandwich panels: Comparison between Budiansky-Fleck-Soutis model and experiments
No full textIn this study, the compressive behaviour of carbon fibre reinforced plastic quasi-isotropic laminates and sandwich panels with carbon fibre reinforced plastic face sheets and syntactic foam core has been investigated. Experimentally determined open hole strengths have been compared with theoretical predictions obtained by applying a linear cohesive zone model. The unnotched compressive strength has been experimentally determined, and the in-plane fracture toughness has been analytically predicted as input parameters of the model. Buckling phenomena occurred on some specimens, and they have been taken into account. Evaluation of macroscopic failure modes in compression tests on unnotched specimens led to a better understanding on the advantages of the analytical model and on the possibility of applying the model to sandwich structures. The experimental results were in good agreement with the analytical prediction by the Budiansky–Soutis–Fleck cohesive zone model, and the difference between theoretical and experimental open hole strengths of Syncore sandwich panels wa
A method for the production of carpet plots for notched compression strength of carbon fibre reinforced plastic multidirectional laminates
No full textThis paper outlines a newly developed method for the calculation of the notched compression strength of carbon fibre reinforced plastic (CFRP) laminates. The BAe-Warton laminate strength prediction method (1) is used to predict the unnotched strength of the laminate and the Soutis et al. model (2) to predict the notch effect. Notched and unnotched strengths are reported for a wide range of T800/924C and T800/5245C carbon fibre-epoxy multidirectional laminates with 0°, ± 45° and/or 90° lay-ups; results are compared with theoretical predictions and in most cases the error is less than 10 per cent. Carpet plots of open hole compression strength for different T800/5245C lay-ups tested at room temperature (RT)/dry and 100 °C/wet are produced. Finally, the open hole strengths generated by the Soutis et al. (2) model are factored by using appropriate experimental data to allow for plain and countersunk filled holes. © IMechE 1997
Modelling the compressive response behaviour of monolithic and sandwich composite structures
No full textFailure in compression of fiber composite laminates with an open hole is by the initiation and growth of a microbuckle from the edge of the hole. The geometric inhomogeneity induces fiber rotation under increasing applied load; deformation localizes within a band and a microbuckle is initiated. The microbuckle then propagates in a stable manner for 2–3 mm and the component fails at a higher load than the initiation load. This process in carbon-epoxy and carbon-PEEK laminates was compared to an equivalent crack containing cohesive stresses. It is a crack bridging analysis that predicts the size of the buckled region as a function of the applied load, with the local stress supported by the buckled fibers decreasing linearly with the closing displacement of the microbuckle. The model is able to predict successfully the effects of hole size and lay-up upon the compressive strength and has been incorporated into a user-friendly computer program. Tests had been performed to obtain both the laminate un-notched strength and the compressive energy release rate associated with fiber microbuckling, which are required as the model's input. From a design point of view, it is desirable to predict these laminate properties from the mechanical properties of the fibers and the matrix and from the lay-up geometry
A method for the production of carpet plots for notched compression strength of carbon fibre reinforced plastic multidirectional laminates
No full textThis paper outlines a newly developed method for the calculation of the notched compression strength of carbon fibre reinforced plastic (CFRP) laminates. The BAe-Warton laminate strength prediction method (1) is used to predict the unnotched strength of the laminate and the Soutis et al. model (2) to predict the notch effect. Notched and unnotched strengths are reported for a wide range of T800/924C and T800/5245C carbon fibre-epoxy multidirectional laminates with 0°, ± 45° and/or 90° lay-ups; results are compared with theoretical predictions and in most cases the error is less than 10 per cent. Carpet plots of open hole compression strength for different T800/5245C lay-ups tested at room temperature (RT)/dry and 100 °C/wet are produced. Finally, the open hole strengths generated by the Soutis et al. (2) model are factored by using appropriate experimental data to allow for plain and countersunk filled holes. © IMechE 1997
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