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Carbon fibre–reinforced polymers (CFRP) are increasingly utilised as materials within hybrid components in combination with plastics and metals. Although hybrid components provide a combination of advantages from the constituent materials, there are some challenges for the manufacture of high-quality hybrid components, including weak interface bonding between the constituent materials. This research focuses on utilising additive manufacturing (AM) technology to control an aluminium substrate's surface features to enhance interfacial bonding with a CFRP laminate. For this purpose, different surface structures were designed and manufactured using laser powder bed fusion (LPBF) technology to understand the influence of surface geometry and roughness on the interface. A lattice structure with a unit cell size of 3 × 3 × 1.5 mm was manufactured to create a substrate surface with porosity. A second substrate surface was designed with the same lattice structure; however, the voids were filled to present an equivalent surface topology (EST), excluding porosity. This comparison provides an understanding of the influence of the porosity of the substrate surface on interfacial bonding strength. Interfacial bonding between the aluminium substrates and a CFRP laminate was assessed using short beam strength (SBS) and flatwise tensile tests. The results from the SBS testing indicated a 3D-printed substrate with random surface roughness increased the interlaminar shear strength of the hybrid component by almost 200% compared to a hybrid laminate with non-printed substrate. The results from flatwise tensile tests illustrated that the out-of-plane bonding strength can also be improved significantly (almost 100%).

In this article, coupled electromagnetic-thermal simulations of inductive power transfer (IPT) pads using finite-element simulations are discussed. Derivation of each electrical and thermal parameters required for the modeling process is outlined. Simulation models are used to predict the power loss and the temperature rise of an IPT pad at different ambient temperatures at steady state. Using these simulation methods, the power loss within an IPT pad operating at 50 ${^\circ }$ C ambient temperature is predicted. A 10-KW IPT system is set up within an environmental chamber to validate the predicted losses within the system.

The ferrite magnetic core is an integral component of road-embedded wireless charging systems for electric vehicles. However, the brittleness of ferrite makes it susceptible to premature fracture due to cyclic wheel loading from vehicles. This has motivated the development of a soft magnetic composite (SMC) composed of a flexible polyurethane and crushed ferrite as an alternative. An experimental investigation was conducted into the trade-offs between mechanical, thermal and magnetic properties at ferrite volume fractions between 45.9[Formula: see text]vol% and 80.6[Formula: see text]vol%. A comparison was made between measured properties and predictions from analytical models in order to further investigate the characteristics of the composite. The investigation showed a trade-off between the increase in magnetic permeability and the reduction in strain-to-failure as ferrite volume fraction increased. In addition, a large increase in flexural modulus and thermal conductivity, along with a slight increase in flexural strength was observed. More importantly, the strain-to-failure of the composite was 20 times higher than that of ferrite even at the highest volume fraction, indicating that the SMC was successful in providing a more ductile and flexible alternative.

In this research, two nano-clays, halloysite nano-tube (HNT) and layered double hydroxide (LDH), were employed to compare fire and mechanical properties of epoxy composites based on ammonium polyphosphate (APP) and each of the two nano-clays. The results showed that the combination of APP and nano-clay achieved a significant reduction (approx. 87%) in peak heat release rate of epoxy resin. The comparative analysis also demonstrated that the total heat release of the composite including HNT was approx. 18% lower than that of the LDH based composite. Moreover, HNT generated higher tensile properties in the composite. Overall, the HNT (∼1.5 USD/kg) is a more cost-effective nano-clay than LDH (∼180 USD/kg) to effectively improve the fire resistance and maintain the mechanical properties of epoxy composites.

This paper presents a novel experimental and simulation investigation of quasi-static transverse deformation of 3D printed polymeric Functionally Graded (FG) plates, which obey the distribution of material properties through the length. Graded solid elements with continuous property distribution at different Gauss points were implemented by a user material subroutine (UMAT) in ABAQUS Finite Element (FE) software. In order to validate the proposed graded FE solutions, the original experimental deflection measurements using 3D-Digital Image Correlation (DIC) technique performed to capture transverse deformation of designed and manufactured 3D printed polymeric FG plates. DIC technique involved tracking the motion of geometric features on a specimen surface over the course of an experiment to generate the displacement field experimentally. It was found that the deviation between FE and experimental out of plane deflection for nonlinear FG plates is higher than that of linear FG plates, which is potentially due to the high gradient distribution of the material inclusions. It can be concluded that the presented 3D-digtal image correlation technique provides for transverse deformation of polymeric FG plates. The deflection contours for the FG plate are not symmetric, differences being more prominent for the linear high stiffness ratio combination. The outcomes of this study can be applied to determine the optimum material distribution to produce a controlled-stiffness polymeric FG plate corresponding to prescribed structural characteristics.

The integration of resin flow channels in resin transfer moulding aids manufacturers in numerous ways. They reduce total flow resistance, allowing faster filling, and provide the capability to steer resin flow within a mould. However, the presence of resin flow channels in moulded composites results in local geometric variations affecting fibre alignment . In this work, the static tension and flexural performance of composite laminates with resin flow channel(s) have been investigated. Acoustic emission monitoring was used to characterise damage. The frequency of each distinct damage event was monitored to categorise the damage. Under flexural loads, multiple channel specimens demonstrated damage initiation at lower loads and a high accumulation of AE based damage events when channels were facing the compression side of the bending loads. This study provides insight to the damage mechanism of composites with and without resin flow channels.

International audience; This paper reports the results of an international benchmark exercise on the measurement of fibre bed compaction behaviour. The aim was to identify aspects of the test method critical to obtain reliable results and to arrive at a recommended test procedure for fibre bed compaction measurements. A glass fibre 2/2 twill weave and a biaxial (±45°) glass fibre non-crimp fabric (NCF) were tested in dry and wet conditions. All participants used the same testing procedure but were allowed to use the testing frame, the fixture and sample geometry of their choice. The results showed a large scatter in the maximum compaction stress between participants at the given target thickness, with coefficients of variation ranging from 38 % to 58 %. Statistical analysis of data indicated that wetting of the specimen significantly affected the scatter in results for the woven fabric, but not for the NCF. This is related to the fibre mobility in the architectures in both fabrics. As isolating the effect of other test parameters on the results was not possible, no statistically significant effect of other test parameters could be proven. The high sensitivity of the recorded compaction pressure near the minimum specimen thickness to changes in specimen thickness suggests that small uncertainties in thickness can result in large variations in the maximum value of the compaction stress. Hence, it is suspected that the thickness measurement technique used may have an effect on the scatter.

In this study, we propose a non-destructive modeling framework, with an ability to obtain computational models for numerical prediction of resin flow through 3D fabrics (commonly used in engine fan blade applications) at multiple fiber volume fractions using a single experiment. The work involves extracting real-time geometrical features of two types of 3D reinforcements during an in-situ compaction experiment using micro CT. The 3D image slices obtained at four different thicknesses were converted to computational models. The fiber tows and inter-tow gaps were modeled as distinct phases. The gap analysis and geometrical measurements revealed significant differences in the preform microstructure investigated at different thicknesses. This was followed by a detailed flow analysis using two different commercial software packages. The exported mesh was analyzed in GeoDict® and Ansys Fluent® for through-thickness permeability computations. The governing fluid dynamics equations were solved to obtain the flow field within the inter-tow gaps for representative volume elements. The predicted through-thickness permeability values were in very good agreement with the experimental data.

The paper presents the free vibration analysis of simply supported 3D printed polymeric functionally graded (FG) plates with variation of material stiffness and density along their length. The analytical formulation based on Higher- Order Shear Deformation Theory (HSDT) accounts for both the shear deformation and thickness stretching effect by a sinusoidal variation of the displacement field across the thickness. The problem is then modelled using the finite element (FE) method. The FE solutions are obtained using linear hexahedral solid elements with spatially graded property distribution at different Gauss points, which is implemented by a subroutine (USDFLD) in the ABAQUS FE software. In order to validate the proposed graded FE solutions, experimental tests using Portable Digital Vibrometer (PDV) performed to capture the first natural frequency of designed and manufactured 3D printed polymeric FG plates. It can be concluded that the presented analytical formulation is not only accurate, but also provides for simple prediction of the free vibration of FG plates. Also, the good agreement found between the numerical models and experimental results demonstrates the effectiveness of graded solid elements in the modelling of FG plate vibration.

The high volume production of carbon fibre reinforced plastics needs cost efficient and robust processes. This paper investigates the influence of local textile variation on flow front progression in resin transfer moulding (RTM). To quantify the textile variation, the textile has been tested with laser triangulation, to achieve the thickness profile map of the flat textile preform. This preform is placed in a transparent flow visualisation tool and an oil is injected into the mould via two different flow channel distribution systems. The flow front progression of the fluid is continuously measured from both sides with two cameras. Furthermore, to demonstrate the influence of defects like folds from the draping process on the local filling behaviour, the textile is prepared with an artificial fold, made of additional non-crimp fabric (NCF) strips. The results show how different defects in the textile influence the local filling behaviour and how the additional flow channel distribution system can decrease the effect of these defects.

Primary load-bearing composite structures require high laminate quality. This is achieved by autoclave prepreg processing where high external pressures enhance consolidation. As a result, parts of simple geometry can be manufactured with void contents less than 1%. However, defects such as wrinkles and voids are typically found within more complex structures. This research investigates defect formation within autoclave prepreg processing stages and is focused on concave female corners with high laminate thickness to corner radius ratios. Experimental studies were carried out to investigate the effect of humidity exposure to uncured prepreg on defect formation during the steps of autoclave processing. It is hypothesized that moisture uptake influences uncured prepreg characteristics such as compaction behaviour, interply friction and prepreg tack, and therefore achieved quality following consolidation. Results have shown that defects already occur during the layup and debulking process and that humidity affects the uncured prepreg characteristics and thereby the consolidation quality.

The Wet Compression Moulding (WCM) process is a recently re-introduced production technique increasingly adopted in industry, most commonly in the automotive sector, for high volume production of structural reinforced plastics components. To date, process design parameters have been established through experiences gained by technologists. To develop an understanding of the influence of process and material parameters, two flow visualisation facilities have been developed to investigate the resin application, consolidation, and post-filling stages of WCM. This article presents a study on process parameters, including hold time, resin mass, edge clamping, and press profile. All studied parameters have been shown to influence the magnitude of resin pressure reached at the completion of the consolidation, as well as the required tool clamping forces. The mode of press control is also shown to affect the rate of pressure decay during post-filling, providing a mechanism for reducing void diameter at the onset of resin gelation.

This study investigates the impact behaviour and post-impact performance of polyamide-6 glass fibre reinforced composites, manufactured by thermoplastic resin transfer moulding. Impact test samples were extracted from quasi-isotropic laminates using two different glass fibre sizings, both with a fibre volume fraction of approximately 52%. A previous study showed that one of these sizings enhanced the interfacial strength and Mode I fracture toughness, however, the effects of the sizing on out-of-plane impact is of greater significance in terms of automotive applications. A drop-weight impact tester was used to determine out-of-plane impact performance for both sizings in terms of impact load-induced and energy returned from the striker. High-speed video of the impact response was simultaneously captured. Testing was carried out at three impact energy levels: two sub-penetration and one full penetration. The impact damage area was observed, and the post-damage compression properties of samples were measured to determine the reduction in their strength and stiffness. Results showed that the use of different sizing technologies had little effect on the post-impact compressive properties and that penetration led to only a 29% drop in compression strength. Overall, the outcomes of this work demonstrate the potential of these materials in automotive applications.

A complete simulation process chain has been used to predict the production and subsequent injection of over-braided textile preforms. A range of mandrel geometries and braiding configurations were used to illustrate how these factors affect the resin injection of the part. Braiding simulations were first completed, predicting the geometry of the braided textile throughout the mandrel. Following this, a range of multi-layered unit-cells were modelled, capturing the variations in geometry. These virtual stacks were produced with both no and maximum in-plane ply shift so as to capture the range of stacking configurations possible. Following a compaction simulation of these stacks, their in-plane permeability tensor was predicted and used to identify the permeability of the braided preform at different regions. This was used to predict the propagation of the resin flow front, highlighting the effects that the mandrel geometry, braiding process parameters and stacking method have on the resulting resin injection.

The paper presents an elasto-plastic damage model based on irreversible thermodynamics for the analysis of functionally graded (FG) plates with in-plane material properties variations. The model considers a simple power law function to describe the FG plates as continua with smooth variation of material properties, such as Young’s Modulus, yield stress, plastic material constants and damage parameters. By introducing two independent plastic and damage multipliers, the model is applicable to different types of materials. Employing the operator splitting methodology, a three-step predictor/multi-corrector algorithm is developed that includes an elastic predictor, a plastic corrector, and a damage corrector. Then, the damage finite element (FE) solutions are obtained using linear hexahedral solid elements with spatially graded property distribution (at different Gauss points), and subsequently implemented by a user material subroutine (UMAT) in the ABAQUS FE software. Good agreement is shown between the analytical damage models, the FE solutions and experimental results sourced from the literature. Several numerical examples establish that the present model is not only accurate, but provides a simple approach to predicting damage of different types of materials, including those that demonstrate both elastic-brittle damage and elasto-plastic damage behaviours. Moreover, the presented model effectively describes the continuum damage of FG plates, capturing variation of the damage variable throughout the plane of the plate.

Although good progress was made by two international benchmark exercises on in-plane permeability, existing methods have not yet been standardized. This paper presents the results of a third benchmark exercise using in-plane permeability measurement, based on systems applying the radial unsaturated injection method. 19 participants using 20 systems characterized a non-crimp and a woven fabric at three different fiber volume contents, using a commercially available silicone oil as impregnating fluid. They followed a detailed characterization procedure and also completed a questionnaire on their set-up and analysis methods. Excluding outliers (2 of 20), the average coefficient of variation (c v ) between the participant´s results was 32% and 44% (non-crimp and woven fabric), while the average c v for individual participants was 8% and 12%, respectively. This indicates statistically significant variations between the measurement systems. Cavity deformation was identified as a major influence, besides fluid pressure/viscosity measurement, textile variations, and data analysis. Fil: May, D.. Institut Für Verbundwerkstoffe Gmbh; Alemania Fil: Aktas, A.. National Physical Laboratory; Reino Unido Fil: Advani, S.G.. University Of Delaware; Estados Unidos Fil: Berg, D. C.. Technische Universität Clausthal; Alemania Fil: Endruweit, A.. University of Nottingham; Estados Unidos. Science and Technology Facilities Council of Nottingham. Rutherford Appleton Laboratory; Reino Unido Fil: Fauster, E.. Montanuniversitat Leoben; Austria Fil: Lomov, S. V.. Katholikie Universiteit Leuven; Bélgica Fil: Long, A.. University of Nottingham; Estados Unidos. Science and Technology Facilities Council of Nottingham. Rutherford Appleton Laboratory; Reino Unido Fil: Mitschang, P.. Institut Für Verbundwerkstoffe Gmbh; Alemania Fil: Abaimov, S.. Skolkovo Institute Of Science And Technology; Rusia Fil: Abliz, D.. Technische Universität Clausthal; Alemania Fil: Akhatov, I.. Skolkovo Institute Of Science And Technology; Rusia Fil: Ali, M. A.. Khalifa University Of Science And Technology; Emiratos Arabes Unidos Fil: Allen, T. D.. University of Auckland; Nueva Zelanda Fil: Bickerton, S.. University of Auckland; Nueva Zelanda Fil: Bodaghi, M.. Institute Of Science And Innovation In Mechanical And Industrial; Portugal Fil: Caglar, B.. Koç Üniversitesi; Turquía Fil: Caglar, H.. Koç Üniversitesi; Turquía Fil: Chiminelli, A.. Instituto Tecnologico de Aragon; España Fil: Correia, N.. Institute Of Science And Innovation In Mechanical And Industrial; Portugal Fil: Cosson, B.. Imt Lille Douai; Francia Fil: Danzi, M.. Eth Zürich; Suiza Fil: Dittmann, J.. Universität Stuttgart; Alemania Fil: Ermanni, P.. Eth Zürich; Suiza Fil: Francucci, Gaston Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: George, A.. University Brigham Young; Estados Unidos Fil: Grishaev, V.. Skolkovo Institute Of Science And Technology; Rusia Fil: Hancioglu, M.. Koç Üniversitesi; Turquía Fil: Kabachi, M. A.. Eth Zürich; Suiza Fil: Kind, K.. Universitat Technical Zu Munich; Alemania Fil: Deléglise Lagardère, M.. Imt Lille Douai; Francia Fil: Laspalas, M.. Instituto Tecnologico de Aragon; España Fil: Lebedev, O. V.. Skolkovo Institute Of Science And Technology; Rusia Fil: Lizaranzu, M.. Instituto Tecnologico de Aragon; España Fil: Liotier, P. J.. Université de Lyon; Francia Fil: Middendorf, P.. Universität Stuttgart; Alemania Fil: Morán, J.. Universidad Nacional de Mar del Plata; Argentina Fil: Park, C. H.. Imt Lille Douai; Francia Fil: Pipes, R. B.. Purdue University; Estados Unidos Fil: Pucci, M. F.. Université de Montpellier; Austria Fil: Raynal, J.. Groupe Institut de Soudure; Francia Fil: Rodriguez, E. S.. Universidad Nacional de Mar del Plata; Argentina Fil: Schledjewski, R.. Montanuniversitat Leoben; Austria Fil: Schubnel, R.. Groupe Institut de Soudure; Francia Fil: Sharp, N.. Purdue University; Estados Unidos Fil: Sims, G.. National Physical Laboratory; Reino Unido Fil: Sozer, E. M.. Koç Üniversitesi; Turquía Fil: Sousa, P.. Katholikie Universiteit Leuven; Bélgica Fil: Thomas, J.. Khalifa University Of Science And Technology; Emiratos Arabes Unidos Fil: Umer, R.. Khalifa University Of Science And Technology; Emiratos Arabes Unidos Fil: Wijaya, W.. University of Auckland; Nueva Zelanda Fil: Willenbacher, B.. Institut Für Verbundwerkstoffe Gmbh; Alemania Fil: Yong, A.. National Physical Laboratory; Reino Unido Fil: Zaremba, S.. Universitat Technical Zu Munich; Alemania Fil: Ziegmann, G.. Technische Universität Clausthal; Alemania

Inductive power transfer (IPT) systems have been researched as one of the methods for wireless electric vehicle charging. One aspect often overlooked in IPT systems is the rise of temperature in the pads during operation in applications where active cooling is difficult, such as in a buried structure within a roadway. This paper conducts a thermal analysis of a buried double-D (DD) primary pad in simulations and experimentally validates the findings.

International audience; Resin Infusion is a manufacturing process used to produce fibre reinforced thermo-set polymer components. This process is utilized in a range of industries such as aerospace, automotive, marine, rail and defense and is a cheaper method when compared to other closed mould or autoclave manufacturing methods, particularly as the size of the parts increases. In this study, wet compaction characteristics and behaviour of three glass fibre reinforcements were analyzed, and 2D panels were manufactured with a selection of inlet and vent pressure combinations during both the filling and post-filling stages of the process to achieve control of the final fibre volume fractions. Reinforcement thickness and resin pressure were monitored throughout each experiment and the achieved fibre volume fractions were measured post-manufacture. Void content was analyzed microscopically and related to the respective experimental parameters set. The compaction result fairly predicted the achieved fibre volume fraction of the manufactured part. The possibility of controlling the fibre volume fraction through control of the post-filling pressure was demonstrated. Even though there was a risk of increased void content with some post-filling configurations, the fibre volume fraction could still be controlled without creating voids with careful application of post-filling conditions. ABSTRACT Resin Infusion is a manufacturing process used to produce fibre reinforced thermo-set polymer

Autoclave prepreg processing is commonly used to produce high-quality structural components. Unlike in flat geometries, defects such as corner thickening, wrinkling and voids may be generated within complex structures during processing. This research investigates defect formation within the layup, debulking and consolidation stages of processing, focused on female moulded corners with high thickness to radius ratios. The influence of varying corner radii and proportion of 0°-fibres on the formation and size of corner defects was investigated. The wrinkling severity, corner thickening, and material flow behaviour of the samples was quantified through optical microscopy analysis. To characterise laminate corner-thickness variation following each processing step (layup, debulking, consolidation), a non-destructive laser measurement method was developed. It is demonstrated that corner thickening initially occurs during the layup and debulking process. Visualisation of the prepreg mass flow in corners shows that a higher 0°-fibres content increases the shear flow of the material during consolidation.

Inductive Power Transfer (IPT) technology is a promising solution for wireless charging of Electric Vehicles (EVs). Given the expected uptake of IPT technology for both stationary and in motion in-road charging, many technical challenges regarding the electromagnetic field and thermal aspects need to be overcome to generate cost-effective and reliable solutions. One particular design constraint of in-road IPT systems is the occurrence of local increases in temperature during operation due to power losses in the wireless charging pads. In this paper, safe operating conditions of an enclosed wireless power transfer pad within a pavement model were identified. This aspect has been studied less rigorously compared with the electromagnetic design. This paper presents a numerical thermal analysis of a double-D (DD) prototype IPT primary pad based on two possible configurations; flush-mounted or buried, within a model pavement. A coupled electromagnetic-thermal simulation has been developed to aid in the development of thermally robust in-road IPT systems. In order to validate the proposed two-way coupled electromagnetic-thermal Finite Element (FE) simulations, experiments were performed to capture the evolving thermal field within an IPT primary pad under continuous and periodic duty cycles. This method made possible analysis of the heating patterns and so the identification of internal hotspots within an IPT pad in a roading structure. A thermal camera was used to provide detailed surface temperature distributions, while suitable application of non-metallic Fiber Bragg Grating (FBG) sensing technology enabled a robust technique to measure temperatures within the intense magnetic fields of a high frequency wireless power transfer system to be developed. Comparisons at steady state of the pavement surface temperature distribution, as well as point measurements with the pad and sand, demonstrate good accuracy. The maximum steady state surface temperature occurs at the centre of the sand surface where the IPT pad is placed and is approximately 87 °C and 100 °C for buried and flush-mounted pads, respectively. Moreover, for a 2/3 duty cycle loading, the maximum temperature of the pad tended to an average of approximately 76 °C, while at constant operation the average temperature is 105 °C. Therefore, a 5 min cooling period significantly reduced operating temperatures within the studied model IPT system. In the future, the methodologies proposed in this paper can also be used to improve the design of higher power IPT pads by identifying hotspots and maximum thermal stresses and determination of optimal charging patterns for heat dissipation.

Current production trends and demands for Fibre Reinforced Plastics are exceeding the capabilities of classical, recognised inspection and test methods, especially their capabilities to monitor the mass production of carbon fibre reinforced plastic parts. Novel non-destructive measurement methods to efficiently perform quality assurance within industrial mass production are required. This research is focused on a novel method to assess the properties of textile reinforcements employed in liquid composite moulding processes. This method non-destructively measures the resistance provided by semi-finished textiles to compressive deformation and fluid flow. Rather than calculating permeability using traditional methods, simple measures of injectability of textile reinforcements are determined using an air pulse applied within the stack or preform. On this basis, a simple, mobile prototype device has been developed to support production and quality control to evaluate the injectability and compressibility properties of stacks and preforms and gather information about processes and systems.

This paper presents a non-linear, large strain constitutive approach to modelling the mechanics of fibrous tows. The isotropic and linear St. Venant hyperelastic model was modified to extend its applicability to a transversely isotropic continuum. From this model, a set of large-strain material parameters which resemble the linear-elastic moduli was derived. The non-linear constitutive response of fibrous tows was accounted for through a modelling scheme that incorporates the instantaneous microstructural arrangement of the tows. Tow samples were isolated from the studied textile roll and subjected to a compression study utilising a custom-made tow compression rig, from which a set of material functions that fully defined the constitutive model were generated. The developed model was then implemented as a material subroutine and utilised in a mesoscopic compaction simulation of a multi-layer 2D woven reinforcement. It was found that the constitutive model performed very well in predicting the shape changes and stresses in deforming tows.

The WCM is a novel production technique for fibre-reinforced polymer components. This technique is increasingly adopted in industry, typically in the automotive sector for medium to large-scale production. This process reduces the cost per part significantly by reducing the number of tools and processing steps, relative to Resin Transfer Moulding. To date, the processing variables, their relations and effect on the composite quality have been established through the knowledge gained by technologists. The drive of this research is to develop a fundamental understanding of the impact of process parameters (key process timings and cavity thicknesses, mould closing speed, edge clamping frame dimensions) and material properties (fibre reinforcement compaction response, permeability, and wettability together with test fluid viscosity and surface tension) on textile wetting, impregnation, and resulting composite part quality. In this study, a 480g/m2 non-crimp unidirectional glass fibre reinforcement has been chosen and characterised for compaction response, in-plane, and through-thickness permeability. For ease of handling, motor oil (DTE heavy VG100) has been characterised and used as a test fluid. Two experimental flow visualisation setups have been developed at the CACM to investigate the influence of process and material parameters on initial resin application and textile wetting, and the subsequent compression flow stage.

This paper presents a novel methodology to derive multi-layer textile unit cells directly from μCT scans of real textile specimens. The constructed unit cells are guaranteed to be periodic and free from inter-tow penetrations. Furthermore, no assumptions with regards to the tows’ shape and spatial placement are imposed, which set the proposed technique apart from the state-of-the-art textile unit cell modelling approaches. The methodology can derive various unique unit cells with an arbitrary number of layers and nesting configurations from a given μCT-dataset, which are readily converted to finite element models that contain local information such as fibre fraction and orientation.

Compaction and permeability characterization of fibrous reinforcements is fundamental to liquid composite molding (LCM) processes, given that these fabric properties determine the part thickness, fiber volume content and mold filling time and patterns. In this study, the permeability of three different 3D woven carbon fiber reinforcements (orthogonal, angle interlock and layer-to-layer) was studied, each having a different weave style and z-binder pattern. For all reinforcements, single-cycle and multiple cycle compaction experiments were conducted on dry and saturated samples. The orthogonal preforms were more difficult to compact to the target fiber volume fraction of 0.65, with peak stresses reaching up to 2.3 MPa. Cyclic compaction tests were conducted to highlight the importance of permanent deformation in the reinforcements, when higher fiber volume content is desired via manufacturing using an LCM process. Unsaturated in-plane radial and saturated through-thickness permeability data were obtained at several fiber volume fractions. The orthogonal and layer-to-layer fabrics exhibited greater levels of anisotropy in the plane of flow. The rate of change of in-plane permeability with increasing fiber volume content was lower compared to through-thickness values. The effect of cyclic compaction on permeability was greater in the orthogonal and angle interlock reinforcements. Micrographs of infused samples showed significant permanent deformation of the z-binder yarns, an effect that reduced permeability at high fiber volume contents.

Typically there is variability in the material and geometrical properties of fibre-reinforced composites and this variability is often spatially correlated. Numerical models can predict the response of such panels, but the spatially correlated nature of the variability must be represented within the model. However, characterising spatially correlated variability is problematic. In this study, data is first generated by an automated optical process; light transmissibility measurements are taken of a dry chopped strand mat panel. The consequent image is post-processed to describe the fibre density as a random field using the Karhunen–Loeve decomposition. Previous measurements have shown a strong correlation between the density of the mat and the tensile modulus, so the information is then used to infer the statistics of the stiffness matrix in a Finite Element model. The panel is then cut into beams, from which mobility measurements provide an ensemble of measured mobility and natural frequencies. Subsequent realisations of the random field and corresponding Finite Element model are then used to predict the statistics of the vibration response of the beams and compare well with measured statistics. The method provides an automated approach to the characterisation of spatial variability and hence the prediction of the statistics vibration response.

To date, simulation of the forces exerted on mould tools during RTM and Compression RTM (CRTM) has focused on planar cases. While a flat plate case has some limited validity in practical applications, the majority of applications are for nonplanar geometry components. Such components present a more challenging case to simulate, as the nonplanar geometry introduces an additional out-of-plane shear component to the local tooling stresses as well as effects due to the geometry itself (such as race-tracking in corners). This article presents the first thorough study of mould tooling forces for a nonplanar geometry. A number of RTM and CRTM experiments were undertaken using a truncated-pyramid mould with an acrylic top platen to allow flow front visualization to be undertaken. Repeatability studies showed variations in fill time and peak tooling forces observed during RTM and CRTM cases which could not be accounted for by variation in the sample mass or fluid viscosity alone. This demonstrated that the processes were influenced by the spatial variability in the areal mass of the preforms. The experimental results were also compared to numerical simulations of the processes. Good agreement between experiment and simulation was observed for both RTM and CRTM cases in terms of flow front evolution. Peak forces were also well predicted, within the variability observed in the experimental results; this was partly due to the out-of-plane shear component of the tooling force being well predicted, in combination with the normal component. In addition to the velocity-controlled mould closure cases, force-controlled mould closure was also investigated for CRTM. Good agreement with simulation was also achieved for this complex situation. The range of processes and conditions investigated here show that the simulation package is providing good agreement to experiment for both flow evolution and tooling forces and stresses. POLYM. COMPOS., 36:591–603, 2015. © 2014 Society of Plastics Engineers

Biocomposite panels consisting of biobased thermoset resins (EP, PU, UP, and tannin) and flax fibre reinforcements were produced using the vacuum assisted resin transfer moulding process. Panels based on a conventional chemical-based resin matrix were also produced, and investigated comparatively. Rheometric analyses were performed to evaluate the suitability of these resins for liquid composite moulding. Tensile, shear, and impactbending tests have been carried out to assess the quality and mechanical performance of manufactured laminates. The impregnation quality was assessed by means of ultrasonic-C-scanning and microscopy. It turned out that the properties of the biobased composite panels made of biobased epoxy resin and a biobased UP-resin from the company Nuplex in New Zealand were onlay slightly inferior to those produced with a conventional epoxy resin. A biobased PU-resin from the company USSC in the USA developed voids during curing. A tannin-based resin containing of formaldehyde was not processable.

This study executed an objective comparison between Resin Infusion methods currently used, providing a level comparison in identical circumstances. Six different resin infusion methods including VARTM, SCRIMP, CAPRI, DBVI, VAP, and PI were investigated to discern if the modifications made relevant to the standard VARTM process have a distinguishable effect, and how significant the effect was. Process parameters were found to vary significantly between methodologies, with large differences in infusion time, laminate pressure and relaxation, and resin usage. Fibre volume fractions were found to vary significantly both between methodologies and along the infusion length of some panels. Differences of up to 13% and 10% were found in short beam strength and compression strength between the infusion methods. There was found to be no significant difference in void content between methodologies once the best process parameters had been established, with the exception of PI which resulted in a significant increase.

This paper presents a novel methodology to isolate the individual tow information contained within relatively low resolution µCT scans of real textile specimens. The proposed method can process high fibre fraction (Vf > 0.60) datasets in a fast and automated manner with minimal user interaction. The methodology has been validated qualitatively and quantitatively. The geometric description of the isolated tows can be used to create structured finite element meshes and voxel meshes, that contain the local tow information such as fibre volume fraction and fibre direction using an in-house meshing algorithm. The structured finite element meshes can be used as initial geometry for textile compaction simulations. The voxel meshes can be used directly for a flow simulation to predict the textile permeability. Finally, a methodology to observe the geometrical evolution of the same tows from different µCT datasets is also presented.

All-cellulose composites (ACCs) represent a class of biocomposite that are entirely synthesised from cellulose, resulting in a matrix and reinforcing phase that are chemically identical. The flexural strength, puncture impact strength and unnotched Charpy impact strength of ACC laminates are reported for the first time and compared with conventional biocomposites. In this study, the flexural and impact properties of ACC laminates based solely on a rayon textile were investigated. It is observed that all-cellulose composite laminates exceed the impact properties of most conventional biocomposites. A high level of fibre–matrix adhesion was observed to hinder interlaminar failure. The unique combination of high flexural and impact strength of ACC laminates demonstrates the potential of ACC laminates as a new class of biocomposite.

The Compression Resin Transfer Moulding (CRTM) process is a variant of the traditional RTM process and permits significantly faster fill times. However, the design parameters of CRTM processes must be carefully chosen in order to reduce cycle time, capital layout and running costs, while maximizing final part quality. These objectives are principally governed by the filling and curing phases which are strongly coupled in the case of non-isothermal processes. In this work the composites manufacturing cycle is modelled as a static Stackelberg game with two virtual decision makers (DMs) monitoring the filling and curing phases, respectively. The model is implemented through a Bilevel Multiobjective Genetic Algorithm (BMOGA), in conjunction with the Cascade-Correlation Learning Architecture Neural Network (CCA-NN) for function evaluations. The obtained results are efficient with respect to the objectives of both DMs and provide the manufacturer with a diverse set of solutions to choose from.

International audience; Two experimental setups used to characterise the in-plane and through-thickness permeabilities of reinforcing textiles have been developed and are presented. Both the experimental testing and data processing techniques used have been selected to ensure that the characterisation is completed in an efficient and robust method, increasing the repeatability of tests while minimising user induced errors as well as the time and resources needed. A number of key results and outputs obtained are presented from tests carried out on a plain woven reinforcing textile with a range of number of layers and at different fibre volume fractions.

Moulds used for rigid-tool Liquid Composite Moulding (LCM) processes, namely Resin Transfer Moulding (RTM) and Compression RTM, are often subjected to large internal forces which originate due to resin injection and from the compaction of fibre reinforcements. Appropriate clamping equipment (e.g. press or perimeter clamps) is necessary to equilibrate these forces. An optimal selection (or design) of such clamping equipment calls for an accurate prediction of the tooling forces generated. This work aims to introduce a comprehensive numerical scheme which addresses this issue, including the case of non-isothermal mould filling. A hybrid Finite Element/Finite Difference (FE/FD) methodology is utilised for solving the coupled flow/energy/species equations. A new fibre compaction model, developed in order to reduce computational complexity while maintaining solution accuracy, is implemented into the simulation algorithm. The force predictions obtained for a planar axisymmetric part reveal that the chosen combination of mould and resin temperatures, together with other process variables, plays a crucial role in allowing fast fill times while keeping setup costs low.

Composite materials are increasingly being used in applications in which their fire response is a critical consideration. Environmental concerns motivate the use of natural fibres, but they represent an additional fuel source for combustion, and their composites will perform worse in flammability testing compared to synthetic alternatives. An experimental study is presented, comparing flax fibre reinforced epoxy samples to composites formed from glass fibre reinforcements of similar architecture, reinforcing the same resin system. The flax composites ignite earlier, release greater levels of heat, and their structure deforms significantly during combustion. Further studies are required to increase understanding of the combustion process, if efficient mechanisms are to be found to reduce flammability of natural fibre composites to acceptable levels.

Continuous fibre-reinforced all-cellulose composite (ACC) laminates were produced in the form of a dimensionally thick (>1 mm) laminate using an easy-to-use processing pathway termed solvent infusion processing (SIP) from a rayon (Cordenka™) textile using the ionic liquid 1-butyl-3-methylimidazolium acetate. SIP facilitates the infusion of a solvent through a dry cellulose fibre preform with the aim of partially dissolving the outer surface of the cellulose fibres. The dissolved cellulose is then regenerated by solvent exchange to form a matrix phase in situ that acts to bond together the undissolved portion of the fibres. SIP is capable of producing thick, dimensionally stable ACC laminates with high volume fractions of continuous fibres (>70 vol.%) due to the combination of two factors: (i) homogeneous and controlled partial dissolution of the fibres and (ii) the application of pressure during regeneration and drying that provides a high level of fibre compaction, thereby overcoming void formation associated with material shrinkage. The effect of inlet and outlet positioning, and applied pressure on the macro- and microstructure of all-cellulose composites is examined. Finally, SIP expands the applications for ACCs by enabling the production of thick ACC laminates to overcome the limitations of conventional thin-film ACCs.

Ambient temperature curing epoxy resins are widely used as the matrix material in fibre reinforced plastics in the marine and wind energy sectors, where they are popular due to their relatively high mechanical performance yet low processing and tooling costs. To date, the characterisation of ambient curing epoxy resins has been limited to relatively simple measures, not suitable for use in heat transfer and flow process models. A complete cure kinetics and rheology model allows the prediction of the progression of degree of cure and viscosity for any time–temperature history. The progression of degree of cure of two epoxy resin systems was measured by differential scanning calorimeter and fitted to an nth order model incorporating vitrification effects. Viscosity was measured using an oscillatory rheometer and fitted to a model from the literature. The resulting cure kinetics and rheology model enables the improvement of resin infusion and wet layup processes by providing a thorough understanding of the interlinked relationship between time, temperature, degree of cure and viscosity.

This paper presents a novel optical technique to quantify in-plane geometric variations within dry glass fibre reinforcement materials. Samples of up to 290 × 450 mm can be examined. Three different reinforcement structures have been studied; a random mat, a plain weave and a stitched bi-axial fabric. Using an empirically derived function, reinforcement areal weight has been predicted locally from a single reinforcement photograph. It was found that areal weight predictions were typically within 5% of experimentally obtained values for 25.4 mm square samples. For periodically structured (woven or stitched) reinforcements, local information describing the tow orientation and geometry has been collected automatically. Manual verification of the reinforcement geometry showed good agreement with the automated technique. 3D textile models have been created within a textile modelling software that include the measured variability.