Search

To meet the processing requirements of resin transfer moulding (RTM) technology, reactive diluent containing m-phenylene moiety was synthesized to physically mixed with phenylethynyl terminated cooligoimides with well-designed molecular weights of 1500−2500 g/mol derived from 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 3,4'-oxydianiline (3,4'-ODA) and m-phenylenediamine (m-PDA). This blend shows low minimum melting viscosity (

Fibre Reinforced Plastic (FRP) materials are widely used in several key engineering applications such as ships, aircraft, wind turbine blades, helicopter blade, automobiles, and other transportation vehicles because of their mechanical properties and tailoring capabilities.Carbon and glass fibres are the most popular fibre reinforcements used for composite components. In the present study, two different stacking sequences, (0 degrees) and (0/90 degrees), are selected to study effect of fibre hybridization on flexural performance using three-point bending tests. Materials used are E-glass and T-300 carbon fibres in an epoxy matrix and the laminates were produced by resin transfer moulding methods. Fracture surfaces of composite laminates were examined using a scanning electron microscope. The results showed that the flexural strength, modulus and strain at failure of unidirectional and bidirectional composite laminates were strongly influenced by stacking sequences, fibre orientation and the hybrid ratio of the fibres. A higher flexural modulus was achieved when carbon fibres were placed on the compressive side. Hybrid specimens showed higher flexural strength and modulus by 21.08% and 145.39%, respectively, compared to the pure glass fibre reinforced laminates. On the other hand, flexural strength and modulus of hybrid specimen were less by 6.50% and 8.20%, respectively, as compared to carbon fibre reinforced specimens. Stacking sequences and hybrid ratio of glass/carbon fibre reinforced specimens were investigated with a view towards improving the mechanical properties of hybrid composites.

Vacuum-assisted resin transfer molding (VARTM), used in manufacturing medium to large-sized composites for transportation industries, requires non-woven mats. While non-woven glass mats used in these applications are optimized for resin impregnation and properties, such optimized mats for natural fibers are not available. In the current research, cattail fibers were extracted from plants (18–30% yield) using alkali retting and non-woven cattail fiber mat was manufactured. The extracted fibers exhibited a normal distribution in diameter (davg. = 32.1 µm); the modulus and strength varied inversely with diameter, and their average values were 19.1 GPa and 172.3 MPa, respectively. The cattail fiber composites were manufactured using non-woven mats, Stypol polyester resin, VARTM pressure (101 kPa) and compression molding pressures (260 and 560 kPa) and tested. Out-of-plane permeability changed with the fiber volume fraction (Vf) of the mats, which was influenced by areal density, thickness, and fiber packing in the mat. The cattail fibers reinforced the Stypol resin significantly. The modulus and the strength increased with consolidation pressures due to the increase in Vf, with maximum values of 7.4 GPa and 48 MPa, respectively, demonstrating the utility of cattail fibers from waste biomass as reinforcements.

Tensile strength and impact toughness of inter-layer hybrid composites, made of twill woven E-glass fabric and unidirectional carbon fiber in epoxy resin matrix with/without surface crack, were experimentally investigated. Hybrid laminates with eight, ten and twelve layers were prepared by employing the vacuum-assisted resin transfer molding method, while carbon and E-glass layers were stacked in an alternating sequence. Specimens were cut for uniaxial tensile loading, low-velocity Charpy impact tests, and for resin burn-off process, while additional specimens with standard artificial surface crack were also prepared for the tensile tests. The results of the quasi-static tensile tests surprisingly showed that tensile properties are a function of number of layers. It is seen that, ultimate tensile stress increases with number of plies by 20 ± 6% and 38 ± 11%, on an average basis for the uncracked and cracked specimens, respectively. This increase is less pronounced for ultimate strain and initial tensile modulus. As for the impact toughness of the specimens, those with twelve layers showed the largest toughness. In all cases, the rate of increase in mechanical properties decreases with increasing number of layers. It is also shown that the existence of surface crack generally increases the ultimate strain at the expense of a drop in ultimate tensile stress, because the laminates are more glass dominated. Reinforcement efficiency factors for uncracked specimens were found to be the constant value of 0.37. A detailed failure analysis has been also presented by scanning electron microscopy of the fracture surface. Charpy impact tests revealed that impact toughness of hybrid laminates increases with the number of layers. Failure modes are reported qualitatively in macroscopic and microscopic scales.

Compression resin transfer molding using inflatable seals is a new variant of LCM (“Liquid composite molding”) processes, which uses the inflatable seals to compress the fiber reinforcements and drive the resin to impregnate the fabric preform, resulting to fill the entire mold cavity. During resin injection, the preform is relaxed. Consequently, the resin enters easily and quickly into the mold cavity. After, the necessary resin is injected into the mold cavity, the compression stage takes place, in a stepwise manner, by swelling the inflatable seals. The objective of this paper is to present this new process and study the effect of the number of inflatable seals on the filling time.

Filament winding is an advanced technology for fabrication of high-performance composites. Pressure-free fabrication can be achieved for non-planar composites with complicated shapes using resin-immersed twisting fibers. In this study, twisted bamboo fiber (TBF) composites were prepared by a filament winding processing (FWP). Short bamboo fiber (SBF), long bamboo fiber (LBF), and TBF composites were prepared by hot pressing (HP) and resin transfer molding (RTM). The results showed that the bamboo fiber/epoxy resin composites were positively related to the fiber size. The bamboo fiber/epoxy resin composites fabricated by FWP exhibited optimal shear performance, while those generated by RTM exhibited optimized bending performance. Dynamic thermomechanical analysis revealed that composites made by FWP had optimized interfaces. The FWP mechanism of bamboo fiber composites was resin immersion and alignment of TBF; upon resin immersion the TBF were coated by resin and could not enter the internal tubes or parenchyma tissues of the TBF. The TBF was aligned by winding equipment. After heated solidification of the resin, several bubble pores were distributed on both sides of the TBF, whose positions remained static over time. The filament winding processing for bamboo fiber composites enhanced their performance and could lead to the applications in bamboo fibers composites.

S-glass-fiber-reinforced plastic layered composites were prepared by the vacuum-assisted resin transfer molding, and their mechanical properties in relation to different layering types were studied. The effects of layering type and off-axis angle on the tensile and flexural strengths of the composites were clarified. In addition, variations in the intelaminar shear strength and bearing strength by bolted joints as functions of off-axis angle were investigated. Results indicated that the tensile and flexural strengths of the S-glass fiber composites with the 0° lamination were more sensitive to the off-axis angle than those with the 0°/90° orthogonal lamination.

The impact behavior and energy absorption of two types of composite tubes, fabricated from carbon fabrics by the resin transfer molding and from carbon prepregs by the lay-up method, were investigated experimentally and numerically. In impact tests, outward-splaying crush caps with different fillet radii were used. Different types of crushing behavior of the tubes were simulated by the finite-element analysis, including a progressive failure function and considering the possibility of delamination. A comparison with experimental results confirmed that, the finite-element analysis was able to well predict the crushing behavior of the composite tubes, showing that the specific energy absorption of the prepreg composite tubes was always about 20% lower than that of the braided ones.

In the current era of high-strength, lightweight, and durable aircraft components, the need for carbon fiber-reinforced epoxy (CFRP) laminates is highly desired owing to their high specific strength and modulus, low coefficient of thermal expansion, and tunable properties that are unmatched by other materials. However, such components’ catastrophic failure occurs due to the interfacial defects and debonding, thereby reducing service life and economic viability. Therefore, there is a pressing need to enhance the mechanical properties of CFRPs through matrix and fiber modifications and introduce the components’ self-healing ability under a natural trigger. This study assessed the crucial role of “thermoreversible bonds” and graphene oxide (GO) “interconnects”, which worked in tandem toward significantly improving the mechanical properties and imparting self-healing properties in CFRP laminates. The laminates were fabricated with varying percentages of GO-modified epoxy matrix via vacuum-assisted resin transfer molding (VARTM) method. The carbon fibers were covalently modified with bis-maleimide (BMI) to establish a thermoreversible bond with GO at the fiber matrix interface to make interconnects. Flexural strength and interlaminar shear strength (ILSS) values for the optimized GO-modified epoxy laminates with BMI-deposited carbon fibers exhibited a significant increase of 30 and 47%, respectively. After a self-healing cycle triggered at 60 °C, they exhibited a recovery in their ILSS values up to 70%. These improvements are particularly useful for aircraft wings made up of CFRP laminates.

Electromagnetically induced preform resting (EIPR) process is a new version of vacuum-assisted resin transfer molding (VARTM) process which allows manipulation of resin flow during the filling step. The EIPR process enhances the permeability of preform locally in case of undesirable flow front situations. This technique ensures the perfect filling despite the existence of permeability variation. To utilize the EIPR process in a better way, its comprehensive characterization to find the optimum value of key factors and filling simulation of it is necessary. Key factors of the EIPR process (i.e., amplitude, frequency of vibration) and permeability of preform as a material index are recognized as independent factors that must be considered to characterize the process. These factors are considered to establish a mathematical model for the permeability of preforms. Maximum and minimum values of the frequency and amplitude are determined based on the observations in acceptable composite material manufacturing and in-plane permeability characterization. Response surface methodology is used to model the permeability of EIPR process to find the optimum response values of the key factors for selected preforms. To assess the process numerically, EIPR process simulation with the optimum values is conducted on two case studies. These case studies involving two different permeability zones are designed in order for evaluation. In each case, a low permeability preform is employed in the middle of high permeability one to create an artificial problem. Simulation results demonstrate an acceptable accuracy.

In this study, the impact of adding TiO2 nanopowders prepared by hydrothermal-assisted sol-gel method on the mechanical properties of a polyester composite reinforced by glass fibers has been investigated. The nanocomposite was fabricated using vacuum-assisted resin transfer molding (VARTM) with TiO2 nanopowders amount ranging from 0 to 7.5 wt%. The obtained results have shown that, firstly, TiO2 nanopowders are formed of anatase structure with a nanometric size in the range of 10–12 nm. Secondly, the optimum amount of TiO2 nanopowders with enhanced properties of the nanocomposite was around 5 wt%. At optimal conditions and compared to unfilled composites, the microhardness increased from 15 to 21 Hv. This result is in good correlation with the tensile modulus, ultimate tensile strength (UTS) and strain to break (SB) which increased by 14%, 83% and 246%, respectively. Including high specific strength and modulus, good fatigue resistance, a these findings may have interesting industrial applications.

A numerical model is developed for analyzing the filtration of suspension through fibrous media, during the particle-filled resin transfer molding process. The modeling approach is based on a coupling between flow and filtration models, and it is validated by comparison to various experimental results. The effect of process parameters on the distribution of the concentration and retention of particles within the preform was studied. Four parameters were considered: (i) the injection velocity, (ii) the injection pressure, (iii) the initial filler concentration, and (iv) the overflow time and the lost suspension. The obtained results reveal that the particle distribution and retention depend strongly on the initial concentration and the injection pressure, but very weakly on the injection velocity. A comparison between the distributions of the concentration and retention obtained was established with the two injection modes (imposed velocity and imposed pressure). A quasi-uniform distribution is obtained with the injection at imposed pressure, while a significant non-homogeneity in the distribution is observed in the case of injection at imposed velocity. In the latter case, a marked improvement in the distribution of the concentration and the retention of the particles is obtained by modifying the injection strategy. This operation consists of continuing the suspension injection after filling the mold and evacuating the suspension overflow through the vent. It was found that a small volume of lost suspension is enough to significantly improve particle distribution.

Current research investigates the effect of the core-shell (C/SH) particles in composites manufactured using novel thermoplastic Elium® resin and carbon fiber reinforcement of different areal weights, 200 gsm and 400 gsm bi-angle non-crimp carbon fabrics (NCCFs). The core-shell particles were activated using the ex-situ methodology which involves the activation of particles before the Resin transfer molding (RTM) injection process. Recommended particle activation parameters are established after carrying out a detailed microscopic study to understand the melting and flattening behavior of these particles. Static indentation and damping attributes are studied to understand the influence of C/SH particles added novel carbon/Elium® composite in improving the out-of plane properties and dynamic mechanical attributes respectively. The interply regions were also toughened with the addition of 1% core-shell particles and the intensity of load drop has reduced by 20% while comparing the thick and thin ply NCCF/Elium® composites. Microscopic examination has shown that the core-shell particles helped to spread the damage evenly throughout the specimen and absorbed more energy during the static-indentation. Loss factor or damping for thick ply Elium® composite and thin ply epoxy composite is increased by 19% and 16.4% with the addition of 5% and 1% C/SH particles respectively. The underlying reasons for improvement offered by C/SH particles in quasi-static impact and dynamic mechanical tests are also deliberated in this paper.

Flow behavior inside the mold cavity of liquid molding processes such as resin transfer molding (RTM) is important information that is necessary to determine filling time and void formation. Most of the studies found in the literature use isothermal models with Newtonian fluids and constant viscosities. However, for some specific applications, the mold filling time dependence on temperature and the viscosity dependence on time and temperature must be considered to precisely predict the flow advance inside the mold. In this study, a viscosity model, that accounts for temperature and time dependence is coupled with a standard computational fluid dynamics (CFD) model to simulate the resin advance inside an RTM mold cavity. The model is simpler than similar methods that describe viscosity as a function of temperature and resin conversion. Nevertheless, the results show that the proposed model is capable of calculating flow advance, air and resin temperatures, and viscosity changes with time and temperature as expected in actual RTM and correlated processing of thick parts or with low injection pressure or high fiber content.

This paper will discuss the improvement made to increase machine capacity in order to be prepare for incoming demand ramp-up and to free up machine allocation to back-up automotive machine. Using DMAIC methodology (Define, Measure, Analyze, Improve and Control) approach, mold curing time identified as the top contributor during time study of the process with 120 secs consumed time per shot. A Differential Scanning Calorimetry (DSC) and Curability Curve study for molding compound was conducted from both internal and external expertise to get the optimum lower range of cure time. Considering all the quality risk using Risk assessment, the success of reducing Mold curing time from 120secs to 80secs increases 25% machine capacity of transfer Molding for Quad Flat No leads(QFN) / Quad Flat No leads multi-Row(QFN-mR) with significant cost savings. The project was able also to free up 3 molding system to support upcoming products.

From the last few decades, the study of natural fiber composite materials has been gaining strong attention among researchers, scientists, and engineers. Natural fiber composite materials are becoming good alternatives to conventional materials because of their lightweight, high specific strength, low thermal expansion, eco-friendly, low manufacturing cost, nonabrasive and bio-degradable characteristics. It is proven that natural fiber is a great alternative to synthetic fiber in the sector of automobiles, railway, and aerospace. Researchers are developing various types of natural fiber-reinforced composites by combining different types of natural fiber such as jute, sisal, coir, hemp, abaca, bamboo, sugar can, kenaf, banana, etc. with various polymers such as polypropylene, epoxy resin, etc. as matrix material. Based on the application and required mechanical and thermal properties, numerous natural fiber-based composite manufacturing processes are available such as injection molding, compression molding, resin transfer molding, hand lay-up, filament welding, pultrusion, autoclave molding, additive manufacturing, etc. The aim of the paper is to present the developments of various manufacturing processes of natural fiber-based composites and obtained mechanical properties.

This paper presents a simple and computationally efficient multi-scale procedure to predict the macroscopic temperature dependent coefficient of thermal expansion (CTE) of any linearly thermoelastic material from isothermal mechanical simulations only. The approach relies on Levin’s demonstration that, in analytical homogenization, the effective coefficient of thermal expansion is related to the local coefficient of thermal expansion and the stress concentration tensor. For demonstration purposes, this procedure was applied to a 3D woven composite material. The proposed approach was successfully validated with full thermal simulations.

High Pressure Resin Transfer Molding (HP-RTM) is a new variant of composite Resin Transfer Molding (RTM) process that enables a short cycle time and a high composite strength to weight ratio, thus presents a great potential for fabricating automotive structural parts. Due to the high injection pressure, fiber-tow washout is becoming one of the major defects which impact the properties of composite materials. To predict and mitigate the fiber-tow washout problem, approaches of both experimental process optimization and computational prediction are essential. In this paper, an experimental study of fiber-tow washout is undertaken to determine the flow injection limits beyond which the preform deformation can be observed at various fiber volume fractions. A feasibility map is developed for a specific fabric and resin combination. It provides a means to determine the injection rates and fiber volume fractions to fabricate a quality part with minimal in-plane fiber washout due to the hydrodynamically flow-induced force during the HP-RTM process.

The aim of this work is to study the mechanical behavior of a hybrid composite based on polyester thermoset matrix reinforced by a mixture of Luffa (LF) and Glass (GF) fibers. The whole volume fraction of the fibers was limited to 20 vol% in which the LF fraction was varied from 5 vol% to 20 vol%. Composites plates were prepared using the resin transfer molding (RTM) method. The morphology was studied by scanning electron microscopy (SEM), and the mechanical properties of the composites were characterized using tensile, three points’ flexural tests and hardness. Obtained results have shown that the mechanical properties of the hybrid composites were superior to those of polyester/LF composite. The mechanical properties depend on the GF fraction and on the organization of GF and LF sheets in the composite. The analytical modeling of tensile properties showed that the mechanical behavior of these hybrid composites is better described by the model of Hirsch with an adjustable value between 0.37 and 0.55. In addition, the water absorption behavior of these hybrid composites was also investigated during 200 h.

In the present research work, the thermal conductivity of unfilled and marble dust filled needle punched nonwoven jute-epoxy composite is investigated. The hybrid composites are prepared using vacuum assistant resin transfer molding (VARTM) process with varying the wt.% of marble dust (filler) from 0 to 24 wt%. The hot disk transient plane source (TPS) thermal constant analyzer is used to measure experimental thermal conductivity. The analytical thermal conductivity is estimated using different theoretical models and Finite element simulation package ANSYS workbench. Three-dimensional model is used to simulate the thermal conductivity of fabricated composite for various filler concentrations. The Temperature and heat flow are considered as the input parameters, while heat flux is output for the finite element simulation. The experimental results indicate that the thermal conductivity increase with increase the filler wt.% in the composite. The result obtained from the theoretical models and ANSYS are found to be in good agreement with the experimental results.

This work investigates the ultimate tensile strength of the non-crimp glass fiber reinforced polymer composite. Two different angle-ply materials are used for this study. One is of biaxial glass cloth (E-Glass) with ± 45° fiber orientation, and the other is of ± 60° fiber orientation. Laminates are made by the vacuum-assisted resin transfer molding method. Tensile and compression tests are conducted on these two materials. From the experimentation, the ultimate tensile strength of the composite is 176.82 MPa (±45°), which is 18% higher than other research works, which has been achieved with a reduction in the number of layers of the laminates prepared. The compression strength of the composite (±45°) is found to be 151.3 MPa. Also, the mechanical properties of both ± 60° and ± 45° fiber orientation with the same density are compared. The results show that the fiber with ± 45° orientation yielded more strength when compared to the ± 60° fiber orientation.

This work has been developed for a comparative purpose concerning the processing and respective mechanical performance of CFRP composites processed by resin transfer molding (RTM) and compression molding (CM) techniques. Thermal and viscosimetric tests before processing certified the optimal parameter procedure. Both composites were submitted to short-beam shear tests and through microscopy to determine failure mechanisms. CM specimens presented a decrease of 27% in shear strength caused by the presence of macro porosity that induced crack initiation and connection of different delamination plies, causing the speeding up of crack propagation and jump of the interlaminar layer. The low capillary effect and higher viscous force were responsible for macro porosity, inducing heterogeneous impregnation in CM and to the direction reduce in mechanical behavior. On the other hand, more homogeneous impregnation in RTM specimens was responsible for the absence of macro porosity, ensuring higher values of shear strength and lower void volume fraction.

This work deals with the investigation of the synergistic effect of bagasse ash with sisal-banana-kenaf-flax fibers reinforced epoxy composite for their flexural behavior. The composites with three combinations of hybrid fibers viz. sisal/kenaf (HSK), banana/kenaf (HBK), and banana/flax (HBF) with bagasse ash (BGA) as filler material are fabricated using vacuum bag assisted resin transfer molding. Experiments were conducted based on L27 orthogonal array to understand the influence of control factor viz. fiber volume, alkali concentration & BGA over output response. X-ray micro computed tomography analysis was conducted over the developed sample to infer the uniform dispersion of fiber and filler material. The experimental results reveal that the addition of fiber up to 30 vol% depicts better strength and further addition results in a negative impact. Increasing in order of BGA decreases the flexural strength of the developed composites.

In this study, experimental and numerical investigations were carried out in order to determine the mechanical properties and impact response of hybrid composite laminate. The hybrid composite laminate was formed from plain woven carbon fiber reinforced epoxy (CFRE) and plain woven glass fiber reinforced epoxy (GFRE) fiber using VARTM (vacuum-assisted resin transfer molding) process. The mechanical properties of the hybrid composites were determined using tensile test device with a 1 mm/min loading rate at room temperature. In addition, hybrid composites were subjected to low-velocity impact test under different impact energy levels (10, 20, 30, 40 J) for determining the impact response. Moreover, mechanical properties and impact responses of CFRE and GFRE laminates were also determined to compare to those of hybrid composite (HCGFRE). Microstructure analysis was performed to investigate the damage surfaces of the fiber and matrix in the composite material subjected to impact and tensile forces. In numerical analyses, composite damage model (Mat 54) was utilized in LS-DYNA® explicit finite element program to simulate the impact behavior of CFRE, GFRE and HCGFRE laminates. Consequently, the tensile test results showed that hybrid composite laminate behaved more ductile than carbon composite laminate and it exhibited more brittle behavior than glass composite laminate. Also, it was determined that absorbed energy and impact load capacity of HCGFRE composite laminate are between absorbed energy and impact load capacity of CFRE and GFRE composite laminate. It was determined that numerical results indicate a similar tendency with the experimental results.

This article examines the use of fiber Bragg grating sensors for cure monitoring purposes in resin transfer molding processes. Within a resin transfer molding test series a thermoset epoxy-amine resin system was used in combination with a woven flax fiber reinforcement. Particular attention was paid on the location of the optical fiber sensor and its sensitive Bragg grating element inside the mold cavity. Three different installation approaches were tested and the correlation of the corresponding strain response with the actual cure state of the resin system was investigated at 50°C and 70°C isothermal cure temperature, respectively. We could demonstrate that characteristic, conspicuous strain changes are directly related to the sol–gel conversion of the thermoset polymer, which was analyzed considering different approaches for the gel-point detection based on rheological measurements. With the installation of the sensor inside a controllable, capsuled resin volume, we could achieve the most reliable strain response that provides capabilities to give in-situ information of the cure state beyond the gelation point.

The mechanical behavior of hybrid composite laminates under varying strain rates and temperatures was investigated in this study. The hybrid composite laminate is constituted as a sequential stacking sequence of plain-woven carbon-fiber-reinforced epoxy (CFRE) and plain-woven glass-fiber-reinforced epoxy (GFRE) laminates. Vacuum-assisted resin transfer molding (VARTM) process was used to fabricate the composite laminates. Hybrid composite laminates (HCGFRE) were tested under four different strain rates (0.05 min−1, 0.5 min−1, 2.5 min−1, 5 min−1) and three different temperatures (RT, 60 °C, 100 °C). Microstructure analysis was performed to observe the voids, fiber delamination and matrix failure occurring in the composite laminate. In numerical analyses, continuum damage mechanics material model (MAT 58) was utilized in LS-DYNA® explicit finite element program to simulate the mechanical properties of CFRE, GFRE and HCGFRE laminates. It was determined that the tensile strength of all composite laminates is increasing by increasing the strain rates in all temperatures. The continuous damage mechanics material model (MAT 58) was found to be suitable for simulating woven composite laminate under different strain rates and temperatures. In microstructural study, it was not observed significant changes in the microstructure of composite laminates by changing strain rates.

Plain-weave fabric is a kind of fiber preform which has been commonly used in resin transfer molding (RTM) to manufacture polymer composites. However, the edge area of plain-weave fabric is easy to shed yarns which will cause the uneven distribution of permeability between edge channel and center of mold in filling process of RTM. Meanwhile, the uneven distribution of permeability will cause the edge effect and seriously affect the final quality of composite materials. In this paper, a method to numerically calculate the permeability of edge channel which fully considers the edge area of plain-weave fabric is proposed. The experiment and simulation of edge effect in filling process are performed. The results show that the simulation of edge effect which applies the edge channel’s permeability calculated by this method are in good agreement with the experimental results. The research in this paper is meaningful to improve the accuracy of edge effect simulation so as to provide a reference for the design of mold structure.

In this study, glass fiber/epoxy resin/multi-walled carbon nanotubes (MWCNTs) were used to fabricate hybrid composites with biaxial warp-knitted fabrics. The biaxial warp-knitted fabrics were grafted with various amounts of MWCNTs and the hybrid composites were fabricated using the resin transfer molding (RTM) method, subsequently. The fabricated samples were subjected to compression after impact and Charpy impact tests. The hybrid composites exhibited higher compression after impact modulus and strength with 26 % and 17 % compared to the samples without nanotubes, respectively. Moreover, the MWCNTs integrated specimens showed 17 % improvement of Charpy impact strength against specimens without carbon nanotubes in 0 ° degree direction. Fracture surface analysis revealed lower number of cracks and shorter crack propagation lengths in the MWCNTs reinforced specimens. The improvement in mechanical properties of the hybrid composites can most likely be attributed to an increase in interfacial adhesion due to the presence of the carbon nanotubes.

Conformal ablators are low-density composite materials comprising a flexible fibrous substrate and polymer matrix. Recent advancements have improved the efficiency of conformal ablator fabrication ...

Vacuum-Assisted Resin Infusion (VARI) and Resin Transfer Molding (RTM) techniques are the most common techniques for the manufacturing of polymeric composite laminates. The VARI technique has a lot of advantages such as low cost, free voids laminates and the ability to produce complex shapes. However, it has some drawbacks such as poor surface finish and temperature instabilities. On the contrary, the RTM technique can withstand high temperature, producing a good surface finish and complex shape laminates. However, it has a high tooling cost and poor quality laminates due to void contents. In this study, a new technique integrated both VARI and RTM techniques is developed to minimize their drawbacks. This technique involves using a semitransparent composite plate instead of a vacuum bag in the VARI technique. This semitransparent plate takes the inverse shape of the composite laminate similar to the RTM tooling. However, this plate has a low cost compared with RTM tooling and allows monitoring of the resin flow during the infusion process. To validate the integrated technique, the mechanical properties of composite laminates are compared with that produced by hand layup technique (HLT). Moreover, the influence of incorporation of 0.25 wt. % and 0.5 wt. % of titanium dioxide (TiO2) nanoparticle into woven and chopped fiber/epoxy composite laminates was demonstrated. The results indicated that the laminates fabricated by the integrated VARI method showed higher mechanical properties than those produced by the hand-layup technique. Moreover, glass fiber/epoxy filled with 0.25 wt. % of TiO2 nanoparticles gives high mechanical properties.

Relaxation-compression resin transfer molding under magnetic field is a new variant of VARTM (“vacuum assisted resin transfer molding”) process, which uses a flexible magnetic membrane controlled by a magnetic force, in order to govern the relaxation and compression phases by changing the permeability of the fabric preform. Thus permits to the resin to enter easily into the mold and to increase the resin impregnation velocity and the fiber volume fraction. This innovation is based on the application of the TRIZ theory (“the theory of inventive problem solving”), which allows us to answer to the shortcomings and the conflict links exist inside the VARTM processes. The objective of this paper is to present this new process and to study the effect of the current intensity and the separated gap between the flexible magnetic membrane and solenoid on the permeability of the preform.

Thermomechanical modeling of a new double-overmolded optical sensor package, comprising a highly filled, as well as an unfilled, strongly thermally expanding transfer molding compound, is presented. Materials' characterization of the polymers using thermal, thermomechanical, dynamic, and optical correlation methods was used to set up finite element models of the three major steps in the assembly packaging process. The results of the simulation were validated by in-plane stress determination using a piezoresistive integrated circuit measured at various temperatures. In addition, the overall package substrate warpage was optically characterized while loading the sample on a hot plate. Agreement between the measurement and the simulation was only found when the stress-free state of the polymers was set to be at the curing-onset temperature. The results obtained are compared with different levels of complexity on materials' characterization and constitutive modeling and could finally be used for sensitivity analysis of the sensor package design. A thicker and more compliant transparent molding compound in this package was found to reduce the stresses that could cause delamination.

Artificial stone materials (ASM) were produced with an iron ore tailing (IOT) from the disruption of Fundão’s tailing dam, located in Mariana, Minas Gerais State, Brazil. The IOT was separated in 3 powders with different particle sizes: DAG (

The present article highlights the development of hybrid-fiber-reinforced composites using a vacuum-assisted resin transfer molding technique on low-cost flax fibers, carbon fiber, glass fibers and a vinyl ester resin system. Flax fibers are introduced to modulate mechanical properties, green credentials, cost, and the weight of carbon/glass/vinyl ester composites. The hybridization effect of flax, carbon, and glass fibers on mechanical properties, including tensile and flexural strengths, flexural modulus, impact strength, interlaminar shear strength, and damping is evaluated, which is also observed by SEM. The dynamic mechanical analysis was carried out for the composites with a three-point bending mode within a frequency range of 0 to 100 Hz. The results of the experiment reveal that hybrid composites with flax fabric and glass fabric had the highest flexural strength (727.8 MPa) and impact strength (0.171 J/mm2) compared with other composites. The dynamic mechanical analysis also showed that the highest value of Tan δ (0.0722) and damping ratio (2.75 %) were obtained compared with those of other composites.

Unsaturated polyester resins (UPR) and vinyl ester resins (VER) are among the most commercially important thermosetting matrix materials for composites. Although comparatively low cost, their technological performance is suitable for a wide range of applications, such as fiber-reinforced plastics, artificial marble or onyx, polymer concrete, or gel coats. The main areas of UPR consumption include the wind energy, marine, pipe and tank, transportation, and construction industries. This chapter discusses basic UPR and VER chemistry and technology of manufacturing, and consequent applications. Some important properties and performance characteristics are discussed, such as shrinkage behavior, flame retardance, and property modification by nanoparticles. Also briefly introduced and described are the practical aspects of UPR and VER processing, with special emphasis on the most widely used technological approaches, such as hand and spray layup, resin infusion, resin transfer molding, sheet and bulk molding, pultrusion, winding, and centrifugal casting.

In this study, three novel thermoplastic impregnation processes were analyzed towards automotive applications. The first process is Thermoplastic Compression Resin Transfer Molding in which a glass fiber mat is impregnated in through thickness by a thermoplastic polymer. The second process is a melt-thermoplastic Resin Transfer Moulding (RTM) process in which the glass fibers are impregnated in plane with the help of a spacer. The third process, stamp forming of hybrid bicomponent fibers, coats the fibers individually during the glass fiber production. The coated fibers are used to produce a fabric, which is then further processed by stamp forming. These three processes were compared in a life cycle analysis (LCA) against conventional resin compression resin transfer moulding with either glass or carbon fibers and metal processes with either steel or aluminum that can be new, partly or fully recycled using the case study of the production, life and disposal of a car bonnet. The presented LCA includes the main phases of the process: extraction and preparation of the raw materials, production and preparation of the mold, process, and energy losses. To include the life of the analyzed bonnet, the amount of diesel that is used to drive the weight of the bonnet for 300′000 km is calculated. In this LCA, the disposal of the bonnet is integrated by analyzing the used energy for the recycling and the incineration. The results show the potential of the developed thermoplastic impregnation processes producing automobile parts, as the used energy producing a thermoplastic bonnet is in the same range as the steel production., Journal of Cleaner Production, 330, ISSN:0959-6526

The bladder molding process is primarily used in sporting applications but mostly with prepregs. Bladder-Assisted Resin Transfer Molding (B-RTM) presents the tremendous potential to automate and mass produce the complex hollow-composite profiles. Thin-ply, non-crimp fabrics (NCFs) provide excellent mechanical, fracture toughness, and vibration damping properties on top of the weight saving it offers to a final product. However, these fiber architectures are difficult to inject due to the resistance they provide for the polymer flow using the liquid injection process. Therefore, it is mandatory to optimize the process parameters to reduce the time for injection and simultaneously achieve better consolidation. This work presents a first, detailed, experimental case study to successfully inject a low-permeability, thin-ply, complex, thermoplastic tubular structure, and the effect of process parameters, boundary conditions, the associated manufacturing challenges, and proposed solutions are deliberated in this paper.

In this paper, structural design and analysis of a composite boat hull was performed. A resin transfer molding manufacturing method was adopted for manufacturing the composite boat hull. The RTM process is an advanced composite manufacturing method that allows a much higher quality product than the hand lay-up process, and less manufacturing cost compared to the autoclave method. Therefore, the RTM manufacturing method was adopted. The mechanical properties of the various aramid fibers and polyester resin were investigated. Based on this, structural design of boat hull was performed using aramid fiber or polyester. After structural design, the optimized resin infusion analysis for RTM manufacturing method was performed. Through the resin infusion analysis, it is confirmed that the designed location of resin injection and outlet is acceptable for manufacturing.

For fast and complete impregnation in Liquid Composite Molding, knowledge about the permeability of the fibrous reinforcement is required. While development of experimental methods continues, a parallel benchmark effort to numerically characterize permeability is being pursued. The approach was to send out the images of a real fibrous microstructure to a number of participants, in order for them to apply their methods for virtual permeability prediction. Via resin transfer molding a plate was manufactured, using the glass woven fabric Hexcel 01102 (295 g/m²) at a fiber volume content of 54% and a thermoset resin. From this plate, a specimen was scanned using a 3D x-ray microscope at a scan size of 1000 x 1000 x 1000 μm³ and a resolution of 0.521 μm³ per voxel. The sample extracted for the simulations with a size of 523 x 65 x 507 μm³ contains about 400 fibers of a single tow. It revealed a variation of filament diameters between 7.5-9.3 μm and a fiber volume content in average of 56.46% with a variation of 54 - 59% in the individual 2D-slices transverse to the fiber direction. The image segmentation was performed by 2D-slices, to which a Hough transform was applied to detect fiber centers and cross-sections. Then fiber paths were tracked through-out the slices by the closest neighbor algorithm. Finally, fiber paths were smoothened by means of the local regression using weighted linear least squares and a 1st degree polynomial model. The participants received a stack of 973 segmented (binary) 2D-images and a corresponding segmented 3D volume raw-file. They were asked to calculate the full permeability tensor components and fill out a detailed questionnaire including questions e.g. on applied flow models and conditions, numerical discretization and approximation methods, fluid properties etc. The received results scatter considerably over two orders of magnitude, although the participants were provided an already segmented image structure, thus eliminating from the beginning a significant source of variation that could have come from image processing. Model size, meshing and many other sources of variation were identified, allowing further specification of the guidelines for the next step.

An experimental study was performed to characterize the evolution of damage in a unidirectional Non-Crimp Fabric (NCF) carbon fiber/snap-cure epoxy composite under in-plane quasi-static tensile loads. The NCF composites were manufactured using a High Pressure-Resin Transfer Molding (HP-RTM) process and comprised a fast-curing epoxy resin and heavy tow unidirectional carbon fiber NCF layers. Laminates with stacking sequences [0/±45/90] and [±45/0 ] were subjected to axial and transverse quasi-static tensile loads and an in-situ Edge replication (ER) technique was used to capture the damage evolution at predefined intervals. An imprint of the composite microstructure, as observed on the edges of a test coupon, was created on a cellulose acetate replicating tape, which was then observed under the microscope. The onset and progression of ply cracks and delamination, which were the two major damage modes present, were quantified and correlated with the stress-strain curves and changes in stiffness. The influence of stacking sequence and ply thickness are also captured.

3D woven composites are well known for their high strength, dimensional stability, delamination, and impact resistance. They are often used in aerospace, energy, and automotive industries where material parts can experience harsh service conditions including substantial variations in temperature. This may lead to significant thermal deformations and thermally-induced stresses in the material. Additionally, 3D woven composites are often produced using resin transfer molding (RTM) technique which involves curing the epoxy resin at elevated temperatures leading to accumulation of the processing-induced residual stress. Thus, understanding of effective thermal behavior of 3D woven composites is essential for their successful design and service. In this paper, the effective thermal properties of 3D woven carbon-epoxy composite materials are estimated using mesoscale finite element models previously developed for evaluation of the manufacturing-induced residual stresses. We determine effective coefficients of thermal expansion (CTEs) of the composites in terms of the known thermal and mechanical properties of epoxy resin and carbon fibers. We investigate how temperature sensitivity of the thermal and mechanical properties of the epoxy influences the overall thermal properties of the composite. The simulations are performed for different composite reinforcement morphologies including ply-to-ply and orthogonal. It is shown that even linear dependence of epoxy’s stiffness and CTE on temperature results in a nonlinear dependence on temperature of the overall composite’s CTE.

With the development of electronic packaging technology in 5G era, System-in-Package (SiP) module is developing into smaller size and higher integration to realize the multi-functional applications, and the reliability of SiP module, especially the interfacial delamination has become one of the most concerned issues. To predict interfacial delamination precisely through modeling and simulation methodologies, accurate warpage of SiP module should be calculated accordingly since warpage deformation is one of the main reasons of interface delamination. For plastic packaged devices, like most SiP modules, coefficient of thermal expansion (CTE) mismatch between epoxy molding compound (EMC) and its adjacent materials will lead to warpage during the process of transfer molding and post-mold cure of EMC. In addition to this, another important reason of warpage is the chemical shrinkage of EMC during curing process. In this work, a method of characterizing cure shrinkage of EMC was proposed by using bi-material test method. The cure shrinkage rate of EMC was calculated combining the simulation methods and the warpage test results, which was applied in optimizing the SiP module warpage simulation during reflow process. Furthermore, the effect of viscoelasticity of EMC on SiP module warpage was also investigated in this work.

With the continuous improvement on the function of electronics, the IC integration density is gradually increased. Meanwhile, the stacked chip packaging technology appeared to meet the requirements of chip integration. Among them, the cantilever stacked chip structure not only increases the package density, but also satisfies the need of vertically integrated chips with the same size. However, the gold wire sweep induced during the transfer molding process is still one of the critical issues for the reliability of the cantilever stack structure. Therefore, it is of great significance to explore the wire offset in the process of transfer molding to enhance the reliability of stacked chip packaging. In this paper, a mold-flow analysis model of cantilevered chip-stacked structure is setup. The viscoelastic properties were measured by using a DMA analyzer. For studying the deviation of wire loop in transfer molding, the process parameters including the molding temperature, filling time and melt temperature are analyzed by finite element simulation. Firstly, the effect caused by different positions of the gate on the wire offset also is studied. Secondly, the influence of the above process parameters on the position deviation of gold wire is studied following an orthogonal experiment route. The results show that the inhomogeneous temperature field caused by transfer molding has an affect the quality of the chip wire bonding, while the melt temperature has a great influence on the wire offset. Due to the influence of the flow rate of transfer molding, the closer the wire to the gate position is, the larger the offset will be, especially for the wire perpendicular to the gate position.

Today's flip chip scale packaging (FCCSP) microelectronics products are becoming more and more complex, especially in the packaging process using molded underfill manufacturing, which reduces the cost of flip chip technology such as molded underfill (MUF) High, provides molding ability in molding. The problem is to leave effective space under the chip. Generally speaking, this requires a lot of experimental DOE (chip size, substrate design, and epoxy resin type) to solve this problem. For the reasons mentioned above, mold-flow simulation software can be applied to use different flow condition to obtain the best solution as the MUF FCCSP of the substrate structure design. Such a simulation method can help shorten the product development cycle. This article uses the commonly used 3D molding process simulation software for transferring manufacturing process parameters. This article will introduce a comparison of two different structures. A MUF is FCCSP, it is matched with different bump height (SOH) structure comparison (control the flow of different chip bottom space), and observe the difference of the flow melt-front. The second is that there are two different designs on the surface of the substrate (welding masks with completely open or partially open patterns) through the table to enter the previously separated welding mask samples (welding masks with l0um depth structure) to maintain different modes. As this research, we can get a lot of conclusion that improve the molding capability of molded underfill FCCSP in the transfer molding process. If the bottom of the molded underfill FCCSP chip is matched with a structure with a height of 55 µm, then the molding epoxy can easily flow under the area with a large flow space, so the risk of entrapment can be reduced. In addition, the molding compound also has good melt front fluidity, and the fully open substrate surface design of the substrate solder resist layer can achieve more l0µmm space underneath the die area. Then, the CAE output are consistent as the experiment and it can to predict whether the product has a risk assessment of void.

In flip chip packaging, the molded underfill (MUF) integrates the underfilling and molding processes to reduce manufacturing cost and cycle time of process, but is difficlut to obtain high quality filling due to void trapping problem. Virtually, from a technical perspective, it is a microinjection molding process, the MUF process can be thought as a pressure-driven suspension flow. For transfer molding, the main factors affecting the reliability of products include the properties of filling materials, injection process parameters and the geometry of the cavity. In this paper, 3D mold flow modeling of the transfer molding process with MUF using Moldflow is applied. By designing DOE experiments, the MUF process parameters were optimized under different packaging structures of flip chip, and the influence of different methods of chip placement on the molding results was discussed, providing a basis for the design and optimization of process parameters and chip geometry structure.