Composite Molding Research Articles

Accounting for the microstructure in the prediction of the fatigue life of injection moulded composites for automotive applications

Fatigue characterization of injection moulded carbon fibre is conducted on specimens from ten locations on a flat plaque and two locations from an automotive oil pan. Fatigue testing was carried out using tension–tension and fully reversed loading at room temperature and 120 °C using the specimens from the flat plaques. The stiffness and microstructure of the ten locations are used to calibrate a micromechanics model to evaluate the maximum interface stress for the stresses applied during the fatigue tests. Using the peak interface stress as a failure criteria is proposed and verified by the reduction in variability in the fatigue results. The model is validated on the data set for the two automotive component locations under fully reversed loading at 120 °C.

Elastic properties of injection molded short glass fiber reinforced thermoplastic composites

Depending on fiber size and volume fraction, polymer matrix type, processing temperature, injection speed, etc., short fiber reinforced composites produced by injection molding may exhibit complex fiber concentration, orientation and length distributions at different locations, causing large variations in their mechanical properties. In this work, a representative volume element (RVE) scheme is developed to describe the elastic properties of short glass fiber reinforced PA6,6 composites produced by injection molding. In the RVE formulation, fiber length is assumed to follow a two-parameter Weibull distribution, and a new concept, namely preferential angle, is introduced to account for the preferential alignment of fibers at different locations of injection molded composites. A random sequential insertion algorithm is developed to implement the fiber length distribution and fiber preferential alignment, and finite element method (FEM) is employed to analyze the relations of the elastic properties of RVE with three parameters, that is, the mean length, volume fraction and preferential angle of the fibers. Based on the FEM results, quantitative formulas for these relations are obtained. It is found that the variations in the mean length, volume fraction, and preferential angle of the fibers can cause large variations in elastic moduli and elastic anisotropy of the RVE.

Effects of kenaf filler reinforcement on mechanical properties of molded polypropylene composites: A particle size study

The combination of natural fibers in petroleum plastic soften industrial footprints on the environment. Plastic matrix can be filled with renewable resources leading to a greener composite that is biodegradable. This paper focuses on particulate kenaf filler modification and its affects on the properties of polypropylene, processing techniques and the use of particle size filler for improving linkages between fiber and polymeric matrixes.

Investigation of the interfacial adhesion of glass bead-filled multicomponent injection moulded composites

Polymeric materials are often combined with fillers and reinforcements, which modify their properties. The goal can be for example the improvement of thermal and mechanical properties or a reduction in costs. On the other hand, these materials can have negative effects too. In multicomponent injection moulding or in the case of products with weld lines, bonding problems can occur. In this research project, we analysed the effect of glass fibre and glass beads, and the most important technological parameters, melt temperature and holding pressure on the bonding strength between multicomponent injection moulded parts. The test samples were produced with a special injection mould, and the tear-off tests were performed on a tensile testing machine with a grip we developed.

A numerical study of the meso-structure variability in the compaction process of prepreg platelet molded composites

Compaction deformations in a thermoplastic composite system molded from chopped prepreg platelets were analyzed to obtain statistical distributions of local distortions that define the final consolidated meso-structure. This study provides an insight into and allows quantification of the intrinsic geometric variability of the composite meso-structure that controls the variability of the effective composite mechanical properties. A two-phase viscoelastic finite element model was utilized to treat the behavior of molten prepreg platelets, which were assumed to be incompressible and inextensible in the fiber direction during processing. A two-step simulation procedure with discretely modeled platelets and platelet-to-platelet contacts is proposed. The analysis begins with a drop simulation of the uncontrolled material deposition followed by a 3D finite element analysis of the preform compaction and bulk material flow. The proposed model provides a method for generating a composite meso-structure ab initio starting from a statistical sampling of the initial conditions for platelet deposition. The predicted platelet thickness distribution, intra-platelet fiber waviness and out-of-plane platelet undulations were found to be in good agreement with experimental measurements. An estimate of the volume of resin pockets was inferred from the compaction simulation.

Effect of Preheating on Micro-hardness of different Composite Resins

Aim: The aim of this study was to assess the effect of preheating on the surface microhardness of different commercially available composite resins (G-aenial, Filtek Z350 and Tetric-N-Ceram). Materials and Methods: Tubes of the composite resins were either kept at room temperature (24 ±10 C) or preheated for 40 min in a commercially preheating device to 40 0 C, 50 0 C and 60 0C, respectively. From composite resin tubes, a total of 120 disk-shaped specimens (40 specimens of each composite resin, 10 disks from each temperature setting) were prepared by inserting uncured preheated composite resin into cylindrical nylon moulds (5 mm diameter × 2 mm height); before light polymerized for 40s with a light emitting diode curing unit. The Vicker’s microhardness number (VHN) of each specimen was measured. Two-way ANOVA and Tukey test were used to analyze the collected data at a significance level of 0.05. Results: In comparison to the room temperature, there was a significant increase in the mean VHNs of each composite resin by preheating to 40 0C, 50 0 C and 60 0 C, respectively (p<0.05). For G-aenial posterior, Filtek Z350XT and Tetric-N-Ceram, at room temperature, the mean VHNs were 51± 4.3, 60.6± 3.7 and 76.6±1.4, respectively with significant difference between G-aenial posterior and Tetric-N-Ceram (p<0.05), while at 400C, the mean VHNs were 65.7±2.5, 86.8±2.3 and 88.4±1.8, respectively with significant differences (p<0.05) between G-aenial posterior and the other two composites. At 500C, the mean VHNs were 109.4±0.9, 104.4±3.4 and 114±0.71, respectively with no significant difference between composite resins. At 600C, the mean VHNs were 122±3.2, 129±3.4 and 136±2, respectively with significant difference between G-aenial posterior and Tetric-N-Ceram (p<0.05). Conclusions: Preheating significantly increased the surface microhardness of all tested composite resins with the highest value observed for Tetric N-Ceram at 600C preheating temperature.

S-XCT experimental determination of local contact angle and meniscus shape in liquid moulding of composites

In-situ spontaneous wicking experiments were scanned using Synchrotron X-ray Computed Tomography (S-XCT) to study the meniscus shape at the fibre scale. To this end, a single tow of E-glass fibres was impregnated with a commercial epoxy resin by using a wicking fixture specially designed for such purpose. The high resolution of the S-XCT images recorded (0.325μm/pixel) allowed the direct access to the surface of the individual menisci formed between fibres and permitted a direct quantification of the contact angle as well as the local curvature measurement. The contact angle values measured were in good agreement with values reported in the literature. The experimental methodology employed was also compared with numerical results obtained using a surface minimization approach. The results obtained with the simulation tool, in terms of effective capillary pressure and meniscus shape, were in good agreement with the experimental data reported.

Study of Compaction Properties and Permeability Prediction of Multilayered Quadriaxial Non-Crimp Fabric in Liquid Composite Molding Process.

A systematic experimental study was performed to detect the compaction and permeability properties of multilayered biaxial and quadriaxial preforms under vacuum pressure. Compression response on ply level showed that the degree of nesting between quadriaxial NCF was more pronounced and the nesting deformation mechanism was affected by the interaction with stitch yarns. Owing to the meso-channels in the fibrous structure and the nesting between layers, the in-plane permeability of quadriaxial NCF did not follow an inverse proportion relationship with the fiber volume fraction. To predict the in-plane permeability of multilayered quadriaxial NCFs, unit cell models at a high level of geometrical details were built, including local variations in yarn cross-sections and the nesting deformation between layers. Numerical methods were implemented, and the prediction results were in very good agreement with the experimental data. Besides, the major contributing parameters to the enhancement of the in-plane permeabilities were identified by investigating the correlation between permeability and structural parameters of quadriaxial NCF. The modeling methodology and the principles established can be applied to the design of the quadriaxial NCF fabrics, where the permeability enhancement was evidenced.

Life cycle impact assessment of different manufacturing technologies for automotive CFRP components

A comparative life cycle assessment analysis among pressure bag molding and bag molding with autoclave for the manufacturing of car components in carbon fiber reinforced plastic (CFRP) was carried out. Four scenarios were analyzed: i) autoclave bag molding with aluminum mold, ii) autoclave bag molding with CFRP mold and plastic master, iii) autoclave bag molding with CFRP mold and medium density fiberboard master, and iv) pressure bag molding with aluminum mold. The collected data for life cycle inventory derives from an Italian manufacturer of CFRP car components, scientific references and Ecoinvent database. Cumulative energy demand, global warming potential, ReCiPe midpoint and endpoint methods were used as impact and damage categories for quantifying the environmental impacts of the different manufacturing processes investigated. The results showed that the pre-impregnated composite fibers with thermoset polymer matrix, used as input material for the four investigated scenarios, represents the main source of total environmental impact, due to the use of polyacrylonitrile as a precursor for carbon fibers. The comparison among the environmental assessments of the different scenarios demonstrated that the most impacting process is the autoclave bag molding with composite mold and polyurethane master, whilst the most sustainable process is the autoclave bag molding with aluminum mold.

Non-destructive injectability measurements for fibre preforms and semi-finished textiles

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.

3D-printed and injection molded polymer matrix composites with 2D layered materials

Two-dimensional layered materials (2DLMs), MoS2 and WS2, and three-dimensional (3D) graphite were infused in thermoplastic polymer matrices comprised of acrylonitrile butadiene styrene (ABS) and polyethylene terephthalate glycol (PETG). Two processing approaches were examined for creating polymer tensile test specimens using the composites for mechanical testing, which included three-dimensional (3D) printing and injection molding. The ductility generally decreased with the addition of the fillers indicated by an increase in Young’s modulus and a corresponding decrease in yield stress and tensile stress for the 2DLM-polymer composites. The dynamic friction data of the composites were measured in an attempt to exploit the solid phase lubricating properties of graphite and the 2DLM fillers. Graphite proved to lower the dynamic friction in the cases of 3D printed PETG and injection molded ABS, while MoS2 and WS2 were found to reduce friction in 3D printed PETG and ABS. Finally, the thermal conductivities of these polymer matrix composites were measured and compared to the pure polymer matrices. The thermal conductivity increased in both ABS and PETG composites containing graphite, MoS2, and WS2, irrespective of their processing routes. The use of 2DLM-based polymer composites remains an area of interest for a wide range of applications in the future, such as wearable electronics and sensors with low-cost additive manufacturing approaches.

Time-temperature-cure process window of epoxy-vinyl ester resin for applications in liquid composite moulding processes

In this work, a methodology is proposed to develop time–temperature-cure process window of an epoxy-vinyl ester resin using cure kinetics. The cure kinetics of a commercially available epoxy-vinyl ester resin formulated for Liquid Composite Molding (LCM) processing was studied by Differential Scanning Calorimetry (DSC) under isothermal conditions over a specific range of temperature. For isothermal curing reactions performed at 50, 60, and 70 °C, several influencing factors were evaluated using the heat evolution behavior of curing process. Several cure kinetic models were tested to describe the cure kinetics of epoxy-vinyl ester resin. Comparisons of the model solutions with our experimental data showed that the modified Kamal and Sourour three parameter model was capable of capturing both the degree of cure and the curing rate qualitatively and quantitatively. The model parameters were evaluated by a non-linear multiple regression method and the temperature dependence of the kinetic rate constants thus obtained has been determined by fitting to the Arrhenius equation. The model parameters were extrapolated to operate able time- temperature profiles and resin cure evolution behavior was determined.

Carbon Fiber Composite Material Design and Molding Technology and Issues

Carbon Fiber Composite Material Design and Molding Technology and Issues

Experimental Characterization of Dimensional and Surface Alternation of Straight and Angular Cutting on Self-lubricating Composite: A Wire EDM Approach

Demands on better control over the kerf dimension deviation, surface roughness, and corner accuracy are now on the increase for the two-piece aluminum metal composite mold tools. In this investigation, straight and triangular profile cuts attempted with wire electrical discharge machining (WEDM) on the aluminum 6061 self-lubricating composite-reinforced boron carbide (5–15 vol%) and hexagonal boron nitride particles (10 vol% hBN) fabricated using a stir casting method. Rational video measurement showed an increase in B4C particles reduces kerf width dimension deviation only at TON, TOFF and gap voltage (V) parameters. Optical microscope measurement showed an increase in the corner area inaccuracy increases with both low and high pulse-on duration conditions caused by insufficient material removal and a high order of erosion, respectively. There was a large reduction in corner area inaccuracy with increasing wire feed rate. Surface characteristics were examined using a scanning electron microscope (SEM) and XRD to enable observation of the structural damages and recast layers. Composite with 5% boron carbide showed a re-deposition layer over the machined surface, whereas 15% boron carbide composite went through uneven erosion causing the formation of craters and pits on the cutting surface resulting in higher surface roughness.

Polyvinylidene Fluoride/ZnSnO3 Nanocube/Co3O4 Nanoparticle Thermoplastic Composites for Ultrasound-Assisted Piezo-Catalytic Dye Degradation

This work reports a facile, easily retrievable (from treated water), environmentally friendly, ultrasound-assisted piezocatalyst device exhibiting higher reaction kinetics and the lowest degradation time for dyes using a thermoplastic piezocomposite (polyvinylidene-fluoride (PVDF)-zinc stannate (ZnSnO3)-cobalt oxide (Co3O4)). The composite mold (PZC) comprises of hydrothermally grown ZnSnO3 nanocubes interspersed into the PVDF matrix and decorated with Co3O4 nanoparticles by a simple blending and hot molding technique. The orthorhombic structure of ZnSnO3, and β-PVDF were confirmed by XRD, while SEM and FESEM provided a detailed investigation of the composite's morphology. The mold exhibits excellent stability against applied ultrasonic stress without release of ZnSnO3 and Co3O4 particles into treated water and degrades rhodamine B (RhB), methylene blue (MB), and a 1:1 mixture of both dye solutions (RMB) with 100% efficiency within 20 min, which is the fastest time reported so far for piezocatalysis-based dye degradation studies. This enhanced performance is attributed to the synergistic catalytic effect of PVDF in the presence of ZnSnO3 and Co3O4, where ZnSnO3 enhances the polarizability of PVDF, and Co3O4 improves the transport of charge carriers to the surface of the mold for efficient redox reactions. Scavenger testing was performed to confirm the catalytic nature of ultrasonic stress induced dye degradation. Reusability tests revealed 100% efficiency for six consecutive trials. The strategy outlined here can be used for the degradation of a wide variety of complex dyes found in industrial effluents for environmental remediation.

Electrical Heated Epoxy Tool for Rotational Moulding Application

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;The conventional method of making rotational moulding part is by heating the cast aluminium mould or sheet metal mould by hot air medium which has its own limitation on energy loss, the other means is by direct heating and cooling of mould by passing hot oil/water in the mould to have better energy efficiency but leakage and safety problems associated with pumping pressurized hot oil/water. There is no solution available for prototyping rotational moulding parts using design intended material. The current practice of prototyping with the conventional method is expensive and time-consuming. In this work, a simple method is presented to produce a rotational moulded part with a breakthrough in-mould construction, which is Composite Mould Technology (CMT) with glass fibre reinforced epoxy resin built-in with electrical heaters. The project focuses were on proving CMT in comparison with the current production method. CMT reduce the cost by 90% and time to build Protomould by 85%. This electrical heated CMT can be used for new product development (NPD) and very low volume production as the cycle time of the part development was observed very high and life mould is yet to be tested. A deeper study of the life of the mould and associated electrical heater parameters to provide deployment for higher volume production with the improved cost of operation.&lt;/div&gt;&lt;/div&gt;

Capillary wicking in bio-based reinforcements undergoing swelling – Dual scale consideration of porous medium

Capillary wicking of liquids in natural fibrous reinforcements is a significant phenomenon in fibre-reinforced composites manufacturing through Liquid Composite Moulding (LCM) processes. Such phenomenon is however difficult to analyse due to heterogeneous, multiscale and variable fibrous medium during flow. Taking into account the fibre swelling, a modified Washburn’s model is proposed to predict the capillary rise of liquids in flax fibres. Particularly, swelling and wicking are studied at two different scales, i.e. elementary fibres and individual yarns. Swelling effects have been considered in the model and a modified Washburn’s theory has been developed. The proposed model satisfactory fits experimental results from capillary wicking tests, and hold for a 60% fibre volume fraction (Vf) of fabric on a relatively short duration while it fits well on a longer duration for lower Vf.

Manufacture and Strength Analysis of Ergonomic Bicycle Helmet Made from Polymeric Foam Composite Strengthened by Oil Palm Empty Fruit Bunch Fiber with Free Fall Drop Test Method

This article contains a study report on the manufacturing of bicycle helmet models that use polymeric foam composite materials strengthened by oil palm empty fruit bunch (OPEFB). The test results of mechanical polymeric foam obtain tensile stress (σt) 1.17 MPa, compressive stress (σc) 0.51 MPa, bending stress (σb) 3.94 MPa, modulus of elasticity (E) 37.97 MPa, density ( ρ) 193 (kg / m3). The testing results of thermal conductivity (k) with ASTM C177-04 standard obtain 0.096 W/mK. Aerodynamic simulation is carried out on 5 bicycle helmet models with different variations of air ventilation formations and obtained the M4A model that best met the ergonomic criteria. The simulation results of the M4A helmet model are max 65.668 Pa of air pressure (Pu), 26,8 0C of inner wall temperature (Ti), 11.0724 m/s of air velocity (vi) and 0.89 of drag coefficient (CD). Bicycle helmet manufacturing is carried out by hand lay up method for shell layer and casting mold for liner by using GFRP polymer composite molds. Both layers are made by sandwich method with the composition of the shell layer is 100 grams resin, 15 grams glass fiber and 5 grams catalyst. The composition of the liner layer is 275 grams (50%) of unsaturated Polyester 157 BQTN-EX resin, 27.5 grams (5%) of OPEFB fiber, 247 grams (45%) of Blowing Agent Polyurethane and 27.5 grams (5%) of Methyl Ketone Perokside catalyst (MEKPO). The toughness of the helmet is tested by using a free fall drop test with the standard of Consumer Product Safety Commission (CPSC) with the height of impact 1.5 meters. The free fall drop test results are max 2.02 MPa of the impact stress of the M4A bicycle helmet model (σi) and max 283.77 joules of energy impact (Ei) which is close to the Consumer Product Safety Commission’s (CPSC) standard value of 110 joules.

The potential of flax shives as reinforcements for injection moulded polypropylene composites

Flax shives (FS) represent approximately 50 % in weight of dry flax stems, making it the main by-product of the flax scutching industry. Being an available and low-added value lignocellulosic resource, flax shives are an interesting candidate for thermoplastic composite reinforcement. In this study, raw flax shives were fragmented by knife milling using two grids of 500 and 250 μm respectively, while a third batch, with a targeted particle size below 50 μm, was obtained by an attrition beads mill. The fragmentation methods used do not modify the biochemical composition of FS but do reduce their crystallinity due to both crystalline cellulose allomorph conversion and amorphization. The poly-(propylene) and 4%-wt maleic anhydride modified poly-(propylene) injection moulded composites produced with these reinforcing materials have a maximum tensile strength that evolves linearly with particle aspect ratio after processing. The tensile Young’s modulus of the composites reinforced by coarser particles is 3268 ± 240 MPa, which is almost 90 % that obtained for a reference 1mm flax fibre reinforced composite. Furthermore, a basic micromechanical model was applied highlighting the reinforcing capacity of cell wall-like small tubular structures (e.g. flax shives). This study underlines the reinforcing potential of low-value by-product flax shives for value-added composite applications.

Effects of fiber reinforcement on adaptation and bond strength of a bulk-fill composite in deep preparations

ObjectiveThis study investigated the effect of plasma-treated leno weaved ultra-high-molecular-weight polyethylene fiber placement on gap formation and microtensile bond strength (MTBS) of a bulk-fill composite in deep cavity. MethodsResin composite molds (3 mm width, 4 mm depth) were treated with Clearfil SE Bond 2 and restored with 3 techniques : (1) Surefil SDR flow (SDR) placed in bulk (BLK), (2) SDR placed in two unequal increments (INC) and (3) SDR placed after an increment of SDR placed with wetted polyethylene fiber (Ribbond Ultra) at the cavity floor (FRC). As a control, the cavities were bulk-filled with SDR and no bonding agent (n = 12). All the specimens were subjected to real-time and 3D imaging by SS-OCT (1330 nm) to calculate the total volume of gap formed (mm3) at the cavity floor and between the composite increments. For MTBS, the occlusal cavities of the similar dimensions (3 × 3 × 4 mm3) were prepared on extracted molars with similar composite placement techniques (BLK, INC and FRC). After 24 h 37 °C water storage, the specimens were sectioned using a diamond saw to create 0.7 × 0.7 mm2 beams for MTBS, and subjected to bond testing at a crosshead speed of 1 mm/min. Data for both tests was analyzed by one-way ANOVA and multiple-comparisons with Bonferroni correction (α = 0.05). ResultsThe gap volumes were different among the groups (p < 0.05). The largest cavity floor gaps (mm3) were observed in the control group (2.00 ± 0.08); followed by BLK (0.74 ± 0.20) and INC (0.02 ± 0.01). In FRC, the cavity floor was gap-free in all specimens but some separation was observed between the two increments. MTBS values (MPa) were 13.8 ± 7.6, 31.7 ± 12.5 and 28.3 ± 8.5 for BLK, INC and FRC groups. There was no significant difference between FRC and INC and both were different from BLK (p < 0.05). SignificanceGap formation of the bulk-fill composite at cavity floor was significantly reduced with the placement of a fiber-reinforced increment at the base of the deep preparation. The fiber-reinforced increment acts as a shrinkage stress breaker and protects the bonded interface at deep dentin.