Composite Molding Research Articles

A Numerical Framework of Simulating Flow-Induced Deformation during Liquid Composite Moulding

Fibre deformation (or shearing of yarns) can develop during the liquid moulding of composites due to injection pressures or polymerisation (cross-linking) reactions (e.g., chemical shrinkage). On that premise, this may also induce potential residual stress–strain, warpage, and design defects in the composite part. In this paper, a developed numerical framework is customised to analyse deformations and the residual stress–strain of fibre (at a micro-scale) and yarns (at a meso-scale) during a liquid composite moulding (LCM) process cycle (fill and cure stages). This is achieved by linking flow simulations (coupled filling–curing simulation) to a transient structural model using ANSYS software. This work develops advanced User-Defined Functions (UDFs) and User-Defined Scalers (UDSs) to enhance the commercial CFD code with extra models for chemorheology, cure kinetics, heat generation, and permeability. Such models will be hooked within the conservation equations in the thermo-chemo-flow model and hence reflected by the structural model. In doing so, the knowledge of permeability, polymerisation, rheology, and mechanical response can be digitally obtained for more coherent and optimised manufacturing processes of advanced composites.

DESIGN AND MANUFACTURE OF BENT AND VARIABLE SECTION TUBES MADE OF FRP COMPOSITE

Manufacturing of bent composite tubes with variable cross-section is a challenge. The traditional process in composite materials uses retractable mandrels that in case of inflated or bent tubes cannot be applied. The tubular composite elements are often used in high performance bicycles, in the manufacturing of frames, handlebars, saddle pipe supports, etc. This paper presents research on the design of a Mountain Bike (MTB) riser handlebar made of Fiber Reinforced Polymer (FRP). The handlebar is numerically analyzed to estimate the most suitable stacking sequence of Carbon Fiber Reinforced Polymer (CFRP) layers. Depending on the safety standard of bicycle handlebars, a case of longitudinal bending tests was numerically evaluated. Comparing the weight of the CFRP handlebar with the steel handlebar of the same shape, the mass reduction is 5.2 times. The obtained results indicate a two-fold reduction in the weight of the handlebar if it is compared to a handlebar made of aluminum alloys. The research also presents the manufacturing process of the composite mold, and CFRP tubular element. Prepreg CFRP materials are used to manufacture the handlebar, the employed technology being the vacuum bag forming and autoclave curing process.

Effect of fly ash on mechanical properties and microstructural behaviour of injected moulded recycled polypropylene composites

The global challenges of plastic waste and fly ash accumulation demand innovative recycling solutions. In Malaysia, the consumption of 11.2 million tonnes of coal annually generates approximately 2 million tonnes of fly ash, while the recycling of Polypropylene (PP) is hindered by thermo-oxidative and shear-induced degradation during mechanical recycling, resulting in reduced mechanical properties. This study addresses these issues by fabricating recycled PP composites incorporating varying fly ash contents, using a single cycle of mechanical recycling with extrusion and injection moulding methods. The composites were comprehensively tested for tensile, flexural, and compressive strengths, as well as microstructural behaviour. The results reveal a complex relationship between fly ash content and mechanical performance: while tensile strength decreases with increasing fly ash, flexural strength and strain peak at 5 % and 9 % fly ash, respectively. Compressive strength also shows a slight increase up to 7 % fly ash, indicating an optimal range for enhancing mechanical performance. Furthermore, mathematical models were proposed to predict the mechanical properties of rPP – fly ash composites, providing a valuable tool for future material design. These findings demonstrate that optimization of fly ash content can mitigate the effects of polymer degradation, offering a sustainable solution to improving the mechanical performance of this composite.

Study on process optimization of electroless Ni-P plating on binderless WC

Abstract In the field of Precision Glass Molding (PGM), binderless tungsten carbide (WC) is a pivotal material for molds, despite its high processing costs and complexities. Nickel-phosphorus (Ni-P) alloys also exhibit superior performance at elevated temperatures. The innovation of Ni-P/WC composite molds addresses the issue of the poor machinability of WC. This research delves into the influence of the activating solution’s concentration on the surface activation energy of WC, the quality of plating, and the deposition rate during the electroless Ni-P plating process. Additionally, the study scrutinizes how the pH level of the plating solution impacts the quality of Ni-P, the rate of deposition, and the phosphorus content. These investigations have led to the realization of an efficient and high-quality Ni-P plating process for WC.

Research on interface precision control strategy for additive manufacturing of coplanar sand laying with multi-material composite sand mold

Compared with the additive manufacturing of single sand material, it is more difficult to form multi-material composite sand mold. The paper focuses on the influence of sand laying process for the multi-material composite sand mold, explores the change rules in the quality of different curing agent content of composite sand mold, realizes the high quality and high precision sand laying of multi-material sand, and expands the application of composite sand mold in complex structure and high performance products.

Optimizing the injection molding process for thermally and electrically conductive, carbon fiber and carbon nanotube‐reinforced poly(lactic acid) hybrid composites with enhanced mechanical properties

AbstractWe produced poly(lactic acid) (PLA) matrix carbon fiber and carbon nanotube‐reinforced hybrid composites with enhanced thermal conductivity (0.48–0.59 W/mK) and electrical conductivity (0.35–0.97 S/cm). The conductive fillers greatly decreased the toughness, which was compensated with oligomeric lactic acid (OLA). Since fillers and plasticizers greatly alter the flow and thermal properties of the material as well, it was necessary to optimize several parameters of the injection molding process that were predetermined based on theoretical considerations. Based on oscillatory shear rheometry, we explored the rheological behavior of the materials in a wide temperature and shear rate range for the optimum injection molding temperatures, injection volume rates. We showed that by adding 15 wt% OLA as a plasticizer to the composites, the optimal processing temperature decreased by 45–135°C. This remarkable change illustrates the need for rheological studies of PLA compounds. The injection molded hybrid composites containing 5% oligomeric lactic had a tensile strength, modulus of elasticity, and work of fracture higher by 41%, 10%, and 150%, respectively, compared to samples without OLA.

Injection molded lightweight composites from tea-stem fiber and polypropylene: Effect of fiber loading on forming properties and cell structure

China boasts abundant tea resources and substantial production output. To facilitate the high-value utilization of by-products generated during tea production, such as tea stems, thereby reducing resource wastage, this study pioneered the preparation of tea-stem fiber-reinforced polypropylene (TF/PP) composites through microcellular injection and conventional molding processes. The effects of tea-stem fiber (TF) content on the formability of foamed and unfoamed composites were compared and analyzed. The findings reveal that the inclusion of TFs fostered the crystallization of polymer chains, decreased the flowability of the composites in their molten state, and enhanced the density, surface hydrophilicity, and thermal stability of the molded composites. In the unfoamed state, composites with 20 wt%, 40 wt%, and 30 wt% TF content exhibited optimal tensile (35.92 MPa), flexural (58.43 MPa), and impact (6.49 KJ/m2) strength, respectively. Upon foaming, composites with TF contents of 30 wt%, 40 wt%, and 30 wt% demonstrated superior tensile (32.84 MPa), flexural (51.31 MPa), and impact (6.94 KJ/m2) strength, respectively. A 30 % TF content in foamed composites yielded the best reinforcement effect, creating an ideal balance of internal interactions. This resulted in mechanical properties that were close to or even exceeded those of unfoamed PP while reducing the density by nearly 6 %. The results from this study contribute towards the high-value application of tea by-products, promoting the development of the global tea economy.

High performance ultrasonic vibration assisted Wire-arc directed energy deposition of Invar alloy

As the utilization of composite materials flourishes in commercial aircraft, the use of Invar alloy with low coefficient of thermal expansion (CTE) for fabricating composite molds has gained prominence. The large-size composite molds can be fabricated by Wire-arc Directed Energy Deposition (Wire-arc DED), due to its high deposition efficiency and ability to form optimized topologies. However, the Wire-arc DED Invar components still exhibit heterogeneous microstructure, low strength and non-tunable CTE. To address these challenges, this study explores the integration of an ultrasonic energy field during the deposition process to systematically investigate its effects on microstructural evolution, mechanical properties and CTE of Invar alloy. The results reveal that the ultrasonic vibration-assisted deposition significantly refines the grain structure, resulting in a decrease of 81.04 % in grain size compared to the reference state. Moreover, the components fabricated by ultrasonic vibration assisted Wire-arc DED exhibit exceptional properties, with a yield strength (YS) of 408 ± 11.37 MPa, ultimate tensile strength (UTS) of 645 ± 7.61 MPa, and elongation (EL) of 31.3 %. Additionally, the correlation between grain size and CTE was established. The effectiveness of introducing an ultrasonic energy field in improving the mechanical properties and modulating the CTE of the components is further validated by rigorous theoretical calculations. This research provides a promising way to fabricate high performance Invar alloy composite molds.

Shell element-based prediction of process-induced deformation considering the different fabric parameters and stacking sequences of CFRP woven composites

Herein, we present a finite element method (FEM) based curing analysis for predicting the process-induced deformation (PID) of CFRP woven composites using shell-type elements. This method can efficiently consider various fabric parameters and stacking sequences, even for complex structures. For woven composite plates and L-shaped flanges, FEM-based PID prediction using shell elements reduced computation times by 50–59% compared to solid elements, while maintaining acceptable accuracy with relative errors of 0.17–7.35%. Furthermore, the impacts of various fabric parameters and stacking sequences on the PID of woven composites are analyzed in detail. The main finding is that the variation in material properties due to fabric parameters and stacking sequences significantly impacts the PID of woven composite structures. This prediction method can be applied in the design of composite structures and molds, thereby enhancing the dimensional precision and performance of composite structures.

Experimental and numerical analysis of natural fillers loaded and E-glass reinforced epoxy sandwich composites

Natural fibers play a crucial role in sandwich composites due to their biodegradability, ease of manufacturing, and ability to reduce pollution. The research aims to develop new biodegradable polymer composites using pine tree leaves (PTL) fillers loaded with epoxy through hand layup technique with different wt. % of PTL fillers. The molded composites were characterized to analyze the crystal size and plane orientations, surface morphology, thermal resistance, and presence of elemental compositions in the PTL filler-loaded epoxy composites through X-ray diffraction (XRD), Field emission scanning electron microscope (FESEM), Energy dispersive analysis (EDX), Differential scanning calorimetry (DSC), and Thermogravimetric analysis (TGA). The 40 wt % of PTL epoxy composites showed a maximum tensile strength of 32 ± 0.5 MPa, a compressive strength of 15 ± 0.5 MPa, a flexural strength of 55 ± 0.5 MPa, and a Shore D hardness of 73 ± 0.5 SHN. The mechanical strength of 40 wt% PTL fillers loaded epoxy composite was enhanced by adding a single and double layer of E-glass fiber on the bottom and top of the PTL fillers loaded epoxy composite, achieving a maximum tensile strength of 76 ± 0.5 MPa. The 40 wt% PTL fillers loaded double E-glass fiber on the bottom and top of the PTL fillers loaded epoxy sandwich composite attained the maximum tensile strength of 156 ± 0.5 MPa, compressive strength of 29 ± 0.5 MPa, flexural strength of 220 ± 0.5 MPa, and Shore D hardness of 79 ± 0.5 SHN. The PTL fillers loaded and reinforced double E-glass fiber epoxy sandwich composite would be used in low-strength structural applications.

Optimizing the Tensile Strength of Weld Lines in Glass Fiber Composite Injection Molding.

Weld line defects, commonly occurring during the plastic product manufacturing process, are caused by the merging of two opposing streams of molten plastic. The presence of weld lines harms the product's aesthetic appeal and durability. This study uses artificial neural networks to forecast the ultimate tensile strength of a PA6 composite incorporating 30% glass fibers (GFs). Data were collected from tensile strength tests and the technical parameters of injection molding. The packing pressure factor is the one that significantly affects the tensile strength value. The melt temperature has a significant impact on the product's strength as well. In contrast, the filling time factor has less impact than other factors. According to the scanning electron microscope result, the smooth fracture surface indicates the weld line area's high brittleness. Fiber bridging across the weld line area is evident in numerous fractured GF pieces on the fracture surface, which enhances this area. Tensile strength values vary based on the injection parameters, from 65.51 MPa to 73.19 MPa. In addition, the experimental data comprise the outcomes of the artificial neural networks (ANNs), with the maximum relative variation being only 4.63%. The results could improve the PA6 reinforced with 30% GF injection molding procedure with weld lines. In further research, mold temperature improvement should be considered an exemplary method for enhancing the weld line strength.

Analysis of thermal residual deformation using different FVFs for each ply

The thermal stresses and residual deformations in composite materials are caused by differences in the thermal expansion coefficients between the fiber and matrix, chemical shrinkage of the matrix, and temperature distribution during curing. Complex thermal stresses can cause residual thermal deformations, including spring-in, spring-out, and warpage. Consequently, modifying composite molds is time-consuming and labor-intensive.In this study, composite laminate plates were fabricated using the VARTM and VIP processes. For each ply, thermal deformation analysis using different FVFs was performed, and the results were compared with the experimental results. The analysis error of the thermal residual deformations using various FVF for each ply was 9.9–36.1%, which was lower than that using the uniform FVF for all plies. Additionally, the residual thermal deformations caused by the VIP process were smaller than those caused by the VARTM process.

High-Performance 3D Sand Printing Process Using Interlayer Heating

Sand mold 3D printing technology has been recognized as a digital, high-quality, and promising sand mold forming method. However, sand mold 3D printing technology has drawbacks, such as single molding material and long curing time, which limit its further industrial application. Therefore, this study proposes a method for forming composite sand molds based on a layer-stacking structure and a strengthening method based on interlayer heating. The influence of the process parameters on the properties of traditional and composite sand molds was systematically studied. Experimental results demonstrated that when the heating temperature was 150 °C, the enhancement of the sand mold was obvious, with an increase of approximately 20% compared to untreated sand mold. When the composite sand mold with a laminated thickness of 1.5 mm was heated at this temperature, its tensile strength reached 1.53 MPa, and compressive strength reached 5.80 MPa, which met the casting requirements. The composite sand mold printed by interlayer heating has excellent casting performance and economic advantages, which provide theoretical guidance for the high-performance printing of sand molds.

Fabrication of Large-Area Nanostructures Using Cross-Nanoimprint Strategy.

Nanostructures with sufficiently large areas are necessary for the development of practical devices. Current efforts to fabricate large-area nanostructures using step-and-repeat nanoimprint lithography, however, result in either wide seams or low efficiency due to ultraviolet light leakage and the overflow of imprint resin. In this study, we propose an efficient method for large-area nanostructure fabrication using step-and-repeat nanoimprint lithography with a composite mold. The composite mold consists of a quartz support layer, a soft polydimethylsiloxane buffer layer, and multiple intermediate polymer stamps arranged in a cross pattern. The distance between the adjacent stamp pattern areas is equal to the width of the pattern area. This design combines the high imprinting precision of hard molds with the uniform large-area imprinting offered by soft molds. In this experiment, we utilized a composite mold consisting of three sub-molds combined with a cross-nanoimprint strategy to create large-area nanostructures measuring 5 mm × 30 mm on a silicon substrate, with the minimum linewidth of the structure being 100 nm. Compared with traditional step-and-flash nanoimprint lithography, the present method enhances manufacturing efficiency and generates large-area patterns with seam errors only at the micron level. This research could help advance micro-nano optics, flexible electronics, optical communication, and biomedicine studies.

Application of machine learning for composite moulding process modelling

Fibre-reinforced composites are commonly manufactured through moulding processes such as Resin Transfer Moulding (RTM) due to their great reliability and scalability. State-of-the-art RTM process modelling and simulation primarily rely on computationally expensive physics-based modelling methods. Given the great volume of possible input-output combinations, process optimisation via exhaustive physics-based simulations or experiments becomes unfeasible. Hence, this paper proposes the integration of machine learning to facilitate composite moulding process modelling. The well-established PixelRNN, an image-based machine learning model, is employed to model and simulate the complex composite mould filling phenomenon. Upon training and validation, the developed PixelRNN metamodels demonstrated impressive prediction accuracies of up to 97.35 % at 50 % training data proportions, at roughly half the cost of exhaustive simulations. The results of this early study convincingly underscore the promising potential of machine learning in composite moulding applications, particularly when utilising graphical input data rather than the traditional numeric data.

Ceramic Complexes of the Don Settlements of Gorodets and Scythoid Cultures: Experience of Comparative Analysis

The article is devoted to one of the aspects of interaction between two population groups in the forest-steppe Don region. These interactions are related to settlements of the Gorodets and Scythoid cultures of 5th – 3d century BC. In particular, such interactions manifest as transformations of the Gorodets ceramics that gained more dominating Scythoid shapes. The article offers a formalized assessment of common features in the crockery. Previously such assessment was visual. Comparison is imposed on 25 Gorodets and 107 Scythoid modelled kitchen pots. The research compares scaling and the reference profile height and defines the shape similarity index . 22 Gorodets vessels (88%) turn out similar to 69 Scythoid samples (64%). Their similarity indices are 95 to 98%. It is the result of Gorodets potters borrowing crockery shapes from their local neighbours. This should be the consequence of their mutual business. Poorly progressed ethnic mixing is proven by a limited range of Gorodets cookware missing crockery. It is assumed that five Gorodets pots with not really Scythoid profiles and proportions reflect how potters were adapting to acquire new shapes. Scythoid traditions influence is also noticeable in the ceramics production technology. The research compares artificial admixtures detected in the moulding compositions with petrographic analysis imposed on fragments of 80 Gorodets and 108 Scythoid vessels. Both ceramic groups have similar ingredients of the moulding compositions. Among them complex compositions prevail. The study finds eight matching ratios of artificial admixtures with two minor deviations. It proves that different processes mix most probably due to kinship ties of their bearers. Two groups of settled people from the Don forest-steppe interact and make their ceramic materials illustrate dominations of the more socially and economically developed group. However, they do not allow doubts in the ethnocultural authenticity of the Gorodets dwellers.

Effects of Fiber Orientation on the Mechanical Properties of Bidirectional Woven Kevlar Epoxy Composite

Objectives: This study focuses on the mechanical behavior of different fiber orientations of bi-directional woven Kevlar fabric to improve the mechanical properties of the Kevlar epoxy composite materials. Methods: Here in this paper hand moulded composites are fabricated with the Bidirectional plain-woven Kevlar-49, Epoxy resin LY 556 and hardener HT972 and the configuration of the layer was symmetrical and contained 6 plies which arranged as C- (0/45/-45/45/-45/0), B- (0/60/-60/60/-60/0). The standard ASTM D 3039 for tensile test, ASTM D790 for flexural test and ASTM D256 was followed for the laboratory test. F indings: Polymer composite materials are popular due to its weight strength ratio. Bidirectional woven fiber is used for the analysis, where different fiber orientations are compared. From the analysis it is observed that, mechanical properties vary with different fiber orientations. Novelty: In this paper, tensile modulus, flexural modulus, and absorbed impact energy observed in the laboratory to find out the suitability of the Kevlar composite as a building material. The findings of this research are expected to have practical implications for the development of stronger and more durable polymer fiber composites in various structural applications. Keywords Kevlar fiber, Epoxy, Tensile test, Woven fabric, Fiber orientation

Recognition of local fiber orientation state in prepreg platelet molded composites via deep learning

This paper presents a novel deep learning approach for reconstruction of local through-the-thickness fiber orientation distribution (FOD) in discontinuous long-fiber, prepreg-platelet molded composites (PPMC). The thermal-residual strains on composite surfaces are used as inputs to train a fully convolutional neural network, named U-Net, to predict spatially varying, local FOD. High fidelity synthetic data was generated via computational simulation of PPMC with stochastic material orientation state and was used for training the deep learning model. The proposed U-Net model allowed for rapid recognition of PPMC morphology by solving the inverse structural mechanics problem of determining the average fiber orientation through the composite thickness based on the provided surface strain measurements. Upon training and validation, the U-Net deep learning model was deployed to rapidly predict complex distributions of the local through-the-thickness FOD in PPMC.

Terahertz time-domain spectroscopy for the inspection of dry fibre preforms

Liquid moulded polymer matrix composites (LM-PMCs) are increasingly used in aerospace, automotive and other industrial applications. Liquid moulding processes featuring dry fibre preforms provide flexibility and enable cost reductions for secondary load-bearing structures. However, preform variability and manufacturing reproducibility remain major obstacles to wider use in primary structures. The open literature records only marginal use of non-destructive inspection (NDI) methods for dry multilayer preforms due to technological limitations and cost of NDI methods. In this work, terahertz time-domain spectroscopy (THz-TDS) is used for inspecting three dry multilayer glass fibre preforms featuring different defects, for the first time. A novel time-domain enhancement method is compared with classical image processing methods, aiming at improving image contrast and detecting potential defects. Furthermore, THz B-Scan is used for verifying the accuracy of interply defect detection. Finite difference time domain is simulated for analyzing THz magnitude variation in time-domain. Finally, quantitative evaluation is applied to further illustrate the significant potential of THz-TDS for the inspection of dry fibre preforms. The results show that the errors on defects lengths, widths, angles, and diameters for THz-TDS are in the ranges 8.2 %–34.3 %, 18.67 %–75 %, 0.29 %–6.67 %, and 1.33 %–10 % respectively.

Research on the Solid-Liquid Composite Casting Process of Incoloy825/P110 Steel Composite Pipe.

Bimetallic composites have a wide range of application prospects in various industries. Different bonding temperatures, as one of the influencing factors, directly affect the bonding effectiveness as well as the performance and application of the materials. Using metallurgical bonding techniques ensures a strong bond at the interface of bimetallic materials, resulting in high-quality composite pipe billets. This paper describes an Incoloy825/P110 steel bimetal composite material made by the solid-liquid composite method. By utilizing ProCAST 14.5 software for simulation and deriving theoretical formulas, an initial range of temperatures for bimetallic preparation has been tentatively determined. And this temperature range will be utilized for on-site experiments to prepare bimetallic samples. After the preparation process is completed, samples will be selected. The influence of the external mold temperature on the interface bonding of Incoloy825/P110 steel solid-liquid composite material is studied using an ultra-depth three-dimensional morphology microscope and a scanning electron microscope. Through research, the optimal preheating temperature range for the solid-liquid composite outer mold of Incoloy825/P110 bimetallic composite material has been determined. The casting temperature of the inner mold has a significant impact on the interface bonding of this bimetal composite material. As the casting temperature of the inner mold increases, the interface thickness gradually increases. At lower temperatures, the interface thickness is lower and the bonding is poorer. At higher temperatures, melting may occur, leading to coarse grains at the interface. When the temperatures of the inner and outer molds are within a certain range, a new phase appears at the interface. Indeed, it increases the strength of the interface bonding. Due to co-melting of the bimetal near the interface, element migration occurs, resulting in increased Ni and Cr content at the interface and enhanced corrosion resistance.