Pressurized Infusion: A New and Improved Liquid Composite Molding Process

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
M. Akif Yalcinkaya ◽  
Gorkem E. Guloglu ◽  
Maya Pishvar ◽  
Mehrad Amirkhosravi ◽  
E. Murat Sozer ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Composite Laminates ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Compaction Pressure ◽  
External Pressure ◽  
Void Content ◽  
Liquid Composite Molding ◽  
Molding Process ◽  
Fiber Volume

Vacuum-assisted resin transfer molding (VARTM) has several inherent shortcomings such as long mold filling times, low fiber volume fraction, and high void content in fabricated laminates. These problems in VARTM mainly arise from the limited compaction of the laminate and low resin pressure. Pressurized infusion (PI) molding introduced in this paper overcomes these disadvantages by (i) applying high compaction pressure on the laminate by an external pressure chamber placed on the mold and (ii) increasing the resin pressure by pressurizing the inlet resin reservoir. The effectiveness of PI molding was verified by fabricating composite laminates at various levels of chamber and inlet pressures and investigating the effect of these parameters on the fill time, fiber volume fraction, and void content. Furthermore, spatial distribution of voids was characterized by employing a unique method, which uses a flatbed scanner to capture the high-resolution planar scan of the fabricated laminates. The results revealed that PI molding reduced fill time by 45%, increased fiber volume fraction by 16%, reduced void content by 98%, improved short beam shear (SBS) strength by 14%, and yielded uniform spatial distribution of voids compared to those obtained by conventional VARTM.

VARTM Process Improvement for Repeatable and Improved Mechanical Properties of Composite Laminates

2009 ◽  
Author(s):  
Sanjay Sharma ◽  
Dennis A. Siginer
Keyword(s):  
Mechanical Properties ◽  
Process Parameters ◽  
Composite Laminates ◽  
Volume Fraction ◽  
Void Content ◽  
Molding Process ◽  
Fiber Volume ◽  
The Impact ◽  
Vartm Process

Quality of laminates produced by Seeman Composite Resin Infusion Molding Process (SCRIMP) is studied by comparing their Fiber Volume fraction and void content. SCRIMP is a variant of Vacuum Assisted Resin Transfer Molding (VARTM). Manufacturing process parameters are then identified and varied to study the impact on mechanical properties of laminated composites. Modification to SCRIMP is carried out by infusing the resin under additional pressure. Optimal process parameters for this modified SCRIMP process are suggested to yield laminates that are repeatable and consistent in quality. Void content is reduced in the composite laminates by altering the vacuum pressure level. Thickness gradient commonly found in SCRIMP processed laminates is eliminated by allowing longer de-bulking time. Final laminate quality is measured using ASTM standardized mechanical testing.

Optical measurement of local permeability of flax fiber fabrics before liquid composite molding

2018 ◽  
Vol 52 (24) ◽  
pp. 3289-3297 ◽  
Author(s):  
Benoît Cosson
Keyword(s):  
Optical Method ◽  
Fiber Volume Fraction ◽  
Natural Fiber ◽  
Volume Fraction ◽  
Optical Measurement ◽  
Transmission Measurement ◽  
Liquid Composite Molding ◽  
Fiber Volume ◽  
Filling Time ◽  
Composite Molding

Tracking the variability of natural fiber-based fabrics properties, such as local areal weight, fiber volume fraction, and therefore permeability, is crucial to optimize the parts processing of the bio-composites. This paper aims at developing a cost-effective and efficient optical method in order to predict the permeability of flax fabrics used in liquid composite molding processes. This method using an LCD monitor as light source and a reflex camera as a measurement device is based on light transmission measurement through fabric thickness. The raw data given by the camera are gray scale maps, transformed into areal weight maps. FEM software based on levelset method is finally used to highlight the influence of the local variability of the fiber volume fraction, and of the related fabrics porosity and permeability on the mold filling time. The proposed method can be directly implemented on the manufacturing line of the composites. It can be used to optimize, part-to-part, the resin consumption by predicting the resin flow through perform. Interestingly, this novel optical method is auto-calibrated and does not depend on picture resolution.

Effect of Fiber Content on Void Morphology in Resin Transfer Molded E-Glass/Epoxy Composites

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Youssef K. Hamidi ◽  
Sudha Dharmavaram ◽  
Levent Aktas ◽  
M. Cengiz Altan
Keyword(s):  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Void Formation ◽  
Areal Density ◽  
Fiber Content ◽  
Epoxy Composites ◽  
Formation Mechanisms ◽  
Liquid Composite Molding ◽  
Fiber Volume ◽  
Composite Molding

Effect of fiber volume fraction on occurrence, morphology, and spatial distribution of microvoids in resin transfer molded E-glass/epoxy composites is investigated. Three disk-shaped center-gated composite parts containing 8, 12, and 16 layers of randomly-oriented, E-glass fiber perform are molded, yielding 13.5%, 20.5%, and 27.5% fiber volume fractions. Voids are evaluated by microscopic image analysis of the samples obtained along the radius of these disk-shaped composites. The number of voids is found to decrease moderately with increasing fiber content. Void areal density decreased from 10.5 voids/mm2 to 9.5 voids/mm2 as fiber content is increased from 13.5% to 27.5%. Similarly, void volume fraction decreased from 3.1% to 2.5%. Increasing fiber volume fraction from 13.5% to 27.5% is found to lower the contribution of irregularly-shaped voids from 40% of total voids down to 22.4%. Along the radial direction, combined effects of void formation by mechanical entrapment and void mobility are shown to yield a spatially complex void distribution. However, increasing fiber content is observed to affect the void formation mechanisms as more voids are able to move toward the exit vents during molding. These findings are believed to be applicable not only to resin transfer molding but generally to liquid composite molding processes.

scholarly journals Formation of Resin-Rich Zones in Composites Processing

2010 ◽  
Vol 123-125 ◽  
pp. 543-546 ◽  
Author(s):  
Chen Song Dong ◽  
Tze Chiun Tsai
Keyword(s):  
Composite Structures ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Liquid Composite Molding ◽  
Fiber Volume ◽  
Factors Affecting ◽  
Composite Molding ◽  
Composites Processing ◽  
Stress And Deformation ◽  
Fiber Preforms

Resin-rich zones are a common phenomenon in liquid composite molding processes. These resin-rich zones cause unwanted residual stress and deformation, and part-to-part variation, and thus they need to be studied in the design of composite structures. An experimental study on the formation of resin-rich zones in angled composite parts is presented in this paper. Two open-channel mold sets were designed and fabricated. Fiber preforms were loaded into these molds and the gaps formed were visually inspected by a microscope. The influences of corner radius, fiber volume fraction, enclosed angle, and stacking sequence were investigated, and significant factors affecting gap thickness were identified by Design of Experiments (DOE). It can be concluded from the experimental results that: 1) Fiber volume fraction is the most significant factor affecting gap thickness. Gap thickness is inversely proportional to fiber volume fraction; 2) Gap thickness is inversely proportional to radius; 3) The gap thickness of unidirectional preforms is larger than that of the cross-ply preforms.

Effects of vacuum pressure, inlet pressure, and mold temperature on the void content, volume fraction of polyester/e-glass fiber composites manufactured with VARTM process

2011 ◽  
Vol 45 (26) ◽  
pp. 2727-2742 ◽  
Author(s):  
Vishwanath R. Kedari ◽  
Basil I. Farah ◽  
Kuang-Ting Hsiao
Keyword(s):  
Glass Fiber ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Fiber Composite ◽  
Mold Temperature ◽  
Vacuum Pressure ◽  
Inlet Pressure ◽  
Void Content ◽  
Fiber Volume ◽  
Vartm Process

Vacuum-assisted resin transfer molding (VARTM) process is one of the liquid composite molding (LCM) processes aimed at producing high-quality composite parts. The void content and fiber volume fraction of a VARTM part can be affected by many parameters and is critical to the mechanical properties and the quality of the part. In this paper, a series of experiments were conducted with a heated dual pressure control VARTM setup for investigating the effects of vacuum pressure, inlet pressure, and mold temperature on the void content and fiber volume fraction of polyester/E-glass fiber composite. It was found that stronger vacuum and higher mold temperature can better control and increase the fiber volume fraction; however, such a combination of strong vacuum and high mold temperature may also require a reduced inlet pressure for minimizing the void content. The need of pressure reduction can be explained with the compatibility between Darcy's flow and capillary flow in the fiber preform and can be calculated based on the room temperature VARTM results. The experimental results suggest that high mold temperature, high vacuum, and appropriately reduced inlet pressure can produce a VARTM part with high fiber volume fraction and low void content.

Processing Effects on Formation of Microvoids and Hydraulic Fluid Absorption of Quartz/BMI Laminates

2015 ◽  
Author(s):  
Keith R. Hurdelbrink ◽  
Jacob P. Anderson ◽  
Zahed Siddique ◽  
M. Cengiz Altan
Keyword(s):  
Mechanical Properties ◽  
Relative Humidity ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Void Content ◽  
Hydraulic Fluid ◽  
Processing Conditions ◽  
Fluid Absorption ◽  
Fiber Volume ◽  
Fluid Content

Bismaleimide (BMI) resin with Quartz (AQ581) fiber reinforcement is desirable for systems requiring a high glass transition temperature, low dielectric properties, and high laminate mechanical properties. These properties make quartz/BMI an ideal composite material for complex aerospace structures, and are currently being used in various aircraft engine cowlings and radomes. In addition to moisture absorption, quartz/BMI composite laminates are often exposed to different types of hydraulic fluid contaminants, which may lead to anomalous absorption behavior over the service life of the composite structure. Variations in laminate processing conditions, such as prepreg preconditioning and fabrication cure pressure, can have a significant effect on microstructural features of fiber-reinforced composites. Microstructural features, such as fiber volume fraction and void content, can influence mechanical properties and long term absorption of moisture or other liquid contaminants. In this paper, the process-induced microstructure and hydraulic fluid absorption behavior of quartz/BMI laminates are presented. The laminates are fabricated from preconditioned prepregs and cured at different pressures to generate different levels of microvoids, while keeping the fiber volume fraction constant. Location, size and morphology of microvoids are investigated via SEM images obtained from laminates cured at different processing conditions. Composite samples were prepared and fully-immersed in hydraulic fluid at room temperature, and were not subjected to any prior degradation. The laminate samples immersed in hydraulic fluid exhibited clear non-Fickian absorption behavior, which was successfully predicted by the one-dimensional Hindered Diffusion Model (HDM). The degree of non-Fickian absorption behavior, or hindrance coefficient (μ), ranged from 0.30 to 0.72. Model prediction indicates that as the fabrication pressure increased, the maximum fluid content (M∞) decreased considerably. Additionally, a reduction in maximum fluid content was observed when lower relative humidity environments were used for prepreg preconditioning. A discernable difference was not observed in the absorption dynamics when the prepregs were preconditioned at greater than 70% relative humidity.

Compression molding of algae fiber and epoxy composites: Modeling of elastic modulus

2016 ◽  
Vol 37 (19) ◽  
pp. 1202-1216 ◽  
Author(s):  
Alejandra Constante ◽  
Selvum Pillay
Keyword(s):  
Fiber Volume Fraction ◽  
Natural Fiber ◽  
Volume Fraction ◽  
Fiber Composite ◽  
Compaction Pressure ◽  
The United States ◽  
Fiber Composites ◽  
Epoxy Composites ◽  
Natural Fiber Composites ◽  
Fiber Volume

The demand for natural fiber composites in the automotive industry in both Europe and the United States has been forecasted to increase in the coming years. The natural fiber composites based on highly commercialized fibers such as flax, hemp, and sisal has grown to become an important sector of polymeric composites. However, little attention has been addressed to expanding natural fiber composites to include new sources of emerging natural reinforcements, such as reclaimed algae fibers, that have a multiple environmental benefits. Not only are extracted algae fibers biodegradable, the reclamation process has the added benefit of restoring health of waterways choked with algae. This study focuses on the processability of algae fiber–epoxy composites. Short fibers, chemically extracted from raw reclaimed algae, were prepared for natural fiber composite products in two ways. First, randomly oriented mats were produced using the wet-laid process to create layered, compression-molded laminates. Second, loose fibers were dispersed directly into the thermoset matrix to produce a bulk molding compound that was further compression molded into composite lamina. The effect of processing variables such as compaction pressure, temperature, and time were addressed. Moreover, the effect of fiber volume fraction ( υf) and fiber form were considered. Enhanced mechanical properties were found when 56% υf algae fiber was used for the compression-molded laminates composite. This variant exhibited an improvement on the flexural and tensile modulus of 70% and 86% when compared to the neat epoxy. However, the volume of porosity on the same variant was 11% due to lack of compression in some of the fibers. The effect of porosity on the theoretical stiffness was estimated by using the Cox–Krenchel model. Furthermore, an empirical exponential model was formulated to characterize the multi-scale effect of compaction pressure on the overall fiber volume fraction, υf.

Void reduction in VARTM composites by compaction of dry fiber preforms with stationary and moving magnets

2018 ◽  
Vol 53 (6) ◽  
pp. 769-782 ◽  
Author(s):  
Mehrad Amirkhosravi ◽  
Maya Pishvar ◽  
M Cengiz Altan
Keyword(s):  
Composite Laminates ◽  
Volume Fraction ◽  
Compaction Pressure ◽  
Void Content ◽  
Novel Method ◽  
Improved Performance ◽  
Small Parts ◽  
Induced Defects ◽  
Fiber Preforms

Voids are the most common process-induced defects in composite laminates fabricated by vacuum assisted resin transfer molding (VARTM). Reduction or total elimination of these defects is essential for the improved performance and long-term durability of the structural composites. This study introduces a novel method that reduces the void content in VARTM laminates to below 1% by compacting the fibrous mat before infusion. The compaction is achieved by applying magnetic pressure on the vacuum bag by either stationary or moving magnets which are removed before the resin infusion. To assess the effectiveness of the proposed method, 6-, 12-, and 18-ply random mat glass/epoxy laminates are fabricated by VARTM using compacted and uncompacted mats and their properties are compared. In addition, different sets of magnets are used to investigate the effect of compaction levels on the resin flow and the quality of the final part. The placement of stationary magnets on the entire vacuum bag surface is practical for fabrication of small parts. For medium to large parts, however, magnets with a smaller footprint can be moved to apply the compaction pressure over a larger vacuum bag surface. The results show that by applying compaction pressure of 0.2 MPa or higher either by stationary or moving magnets on the dry preforms, the void volume fraction was decreased by 65%–95% to 0.1%–0.8% in all laminates.

Bending Properties of Four-Layer Biaxial Weft Knitted Fabric Reinforced Composite Materials

2012 ◽  
Vol 182-183 ◽  
pp. 89-92
Author(s):  
Liang Sen Liu ◽  
Ye Xiong Qi ◽  
Jia Lu Li
Keyword(s):  
Composite Materials ◽  
Composite Laminates ◽  
Fiber Volume Fraction ◽  
Bending Strength ◽  
Volume Fraction ◽  
Bending Properties ◽  
Fiber Volume ◽  
Reinforced Composite ◽  
Weft Knitted Fabric ◽  
Bending Load

In this paper, a kind of composite laminates whose reinforcement is four-layer biaxial weft knitted (FBWK)fabric made of carbon fiber as inserted yarns has been made. The composite laminates have been impregnated with epoxy resin via resin transfer molding (RTM) technique. The samples of the experiments have been made from the composite laminates. The bending properties of the FBWK fabric reinforced composite materials with different fiber volume fraction have been investigated. The results show that the bending strength of this kind of composites increases with the fiber volume fraction increasing. The bending strength of FBWK reinforced composites with fiber volume fraction of 52% can reach 695.86 MPa. And the relationship between bending load and deflection is obviously linear.

Investigating the Void Content, Fiber Content, and Fiber Orientation of 3D Printed Recycled Carbon Fiber

2019 ◽  
Vol 801 ◽  
pp. 276-281
Author(s):  
Peng Hao Wang ◽  
Ronald Sterkenburg ◽  
Garam Kim ◽  
Yu Wei He
Keyword(s):  
Composite Materials ◽  
Carbon Fiber ◽  
Fiber Orientation ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Aerospace Industry ◽  
Void Content ◽  
Fiber Volume ◽  
3D Printed ◽  
Recycling Techniques

Composite materials continue to grow in popularity within the aerospace industry as the preferred material for manufacturing large airframe structures. However, the popularity of composite materials has also led to the increase in composite waste. As the popularity of composite materials continues to grow, the proper management and recycling of these composite waste materials becomes increasingly crucial to the sustainability of the environment. In order to investigate potential recycling techniques for composite waste, a team of Purdue University School of Aviation and Transportation Technology (SATT) faculty and students teamed up to investigate the characteristics of 3D printed recycled carbon fiber. A prototype 3D printed recycled carbon fiber part was used for the study. Through the use of microscopy and ImageJ image analyzing software, the researchers were able to determine the void content, fiber volume fraction, and fiber orientation of the prototype 3D printed recycled carbon fiber part and identified potential improvements to the 3D printing process in order to improve the 3D printed part’s characteristics.

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