Effect of Moisture Absorption on Mechanical Properties of Resin Transfer Molded Composites

2002 ◽  
Author(s):  
Levent Aktas ◽  
Youssef Hamidi ◽  
M. Cengiz Altan
Keyword(s):  
Mechanical Properties ◽  
Moisture Absorption ◽  
Volume Fraction ◽  
Accelerated Aging ◽  
Fiber Volume ◽  
Fiber Reinforced Polymer Composites ◽  
Short Beam ◽  
Beam Shear ◽  
The Masses ◽  
Fiber Preforms

Fiber reinforced polymer composites are highly susceptible to environmental conditions despite their favorable properties. Among various environmental factors, moisture absorption is known to have significant adverse effects on such materials. This work investigates the effects of accelerated moisture absorption on the mechanical properties of resin transfer molded glass/epoxy composites. 152.4 mm diameter disk-shaped parts are fabricated using EPON 815C resin and EPICURE 3282 curing agent. Reinforcement is provided by four layers of randomly oriented planar glass fiber preforms with 0.459 kg/m2 surface density, yielding approximately 21.2% fiber volume fraction. Samples cut from the molded disks are immersed into boiling water for accelerated aging. The masses of the specimens are measured at periodic intervals to quantity the amount of water absorbed. Tensile and short beam shear tests are performed at different levels of moisture absorption. Mechanical properties are found to decrease as moisture diffused into the material. Fiber pullouts on the surfaces of tested samples show fiber loosening as the cause of material weakening. To investigate the desorption and characteristics, part of the samples are dried at 65°C after the maximum moisture absorption is reached. Total stiffness recovery is observed after desorption but ultimate tensile strenth only recovered by 27.7%, which is 33.4% lower than the initial value.

Experimental Researches on the Mechanical Properties of Three Dimensional Multidirectional Braided Composites

2009 ◽  
Vol 79-82 ◽  
pp. 1237-1240 ◽  
Author(s):  
Ying Sun ◽  
Jia Lu Li ◽  
Li Chen ◽  
Ying Shao
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Braided Composites ◽  
Fiber Volume ◽  
Cut Edge ◽  
Short Beam ◽  
Beam Shear ◽  
Strength And Stiffness ◽  
Braiding Angle

This paper investigated the mechanical properties and the relationships between fiber architecture and the composites properties of three-dimensional multidirectional braided composites made of Toray@T700 carbon fiber impregnated with TDE 86# epoxy resin using RTM. The strength and stiffness properties measured here include tension, compression, flexure and short beam shear, all of these in both the longitudinal and transverse directions. It is found that the 3D six-directional braided composites with 55 % fiber volume fraction and 25°surface braiding angle represent quasi-isotropic in-plane elastic behaviors due to their symmetric, intertwined architecture and unidirectional reinforcements in both the longitudinal and transverse directions. Compared with the tension strength and modulus, those for compressions in the same directions descend near 40% and 10% respectively. The cut-edge on the width destroys the integrity of microstructure and inevitably cuts down the carrying capacity of composites under the longitudinal tension.

Effect of fiber prestressing on mechanical properties of glass fiber epoxy composites manufactured by vacuum-assisted resin transfer molding

2019 ◽  
Vol 39 (1-2) ◽  
pp. 21-30
Author(s):  
Mahmoud Mohamed ◽  
Mohamed M Selim ◽  
Haibin Ning ◽  
Selvum Pillay
Keyword(s):  
Mechanical Properties ◽  
Polymer Composites ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Fiber Reinforced Polymer ◽  
Fiber Reinforced ◽  
Fiber Volume ◽  
Fiber Waviness ◽  
Reinforced Polymer ◽  
Fiber Reinforced Polymer Composites

The mechanical properties of fiber-reinforced polymer composites depend on several aspects such as the characteristics of constituents, fiber volume fraction, and manufacturing techniques. Fiber prestressing is considered a very attractive manufacturing technique that can be used to produce fiber-reinforced polymer composites with high mechanical properties. This technique has the potential to eliminate or reduce some manufacturing problems like fiber waviness. In the present study, a new approach was used to prepare prestressed fiber-reinforced polymer composites. Unidirectional E-glass fiber-stitched mats were impregnated with epoxy matrix through vacuum-assisted resin transfer molding process. Once the infusion was done, a pre-calculated tensile force was applied to the fiber mats through a hydraulic tensile machine. The impregnated fiber mats were left under tension and vacuum during curing of the epoxy matrix (24 h). Five prestressed samples were prepared by using five different prestressing levels 20, 40, 60, 80, and 100 MPa. In addition, non-prestressed (control) sample was prepared for the purpose of comparison. The influence of fiber prestressing on fiber waviness, fiber volume fraction, and void content was investigated. Flexural, tensile, and compression tests were performed to observe the effect of fiber prestressing on the mechanical properties. The results have shown the success of this new approach in producing prestressed fiber-reinforced polymer composites with high mechanical properties comparing to non-prestressed composites. The microstructure analysis has shown dramatical reduction in fiber waviness for the prestressed samples over control sample. All prestressed samples have shown higher fiber volume fraction and lower void content comparing to the control sample. Also the results have shown as the prestressing level increases, fiber volume fraction increase and void content decreases. Prestressing levels of 40 and 60 MPa were found to be the best candidates, they have led to an increase in tensile strength, compressive strength, and flexural strength by 24.2%, 72.5%, 28% and 28.6%, 100.4%, 26.1%, respectively, comparing to the non-prestressed sample. Ease of implementation and promising results of this new approach would attract the attention toward it. Automotive industry is one potential nominee to apply this approach during manufacturing of fiber-reinforced polymer leaf spring.

Monitoring of mechanical properties of prestressed glass fiber epoxy composites over 12 months after fabrication

2021 ◽  
pp. 002199832110047
Author(s):  
Mahmoud Mohamed ◽  
Siddhartha Brahma ◽  
Haibin Ning ◽  
Selvum Pillay
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Flexural Strength ◽  
Compressive Residual Stress ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Epoxy Composites ◽  
Flexural Properties ◽  
Initial Increase ◽  
Fiber Volume

Fiber prestressing during matrix curing can significantly improve the mechanical properties of fiber-reinforced polymer composites. One primary reason behind this improvement is the generated compressive residual stress within the cured matrix, which impedes cracks initiation and propagation. However, the prestressing force might diminish progressively with time due to the creep of the compressed matrix and the relaxation of the tensioned fiber. As a result, the initial compressive residual stress and the acquired improvement in mechanical properties are prone to decline over time. Therefore, it is necessary to evaluate the mechanical properties of the prestressed composites as time proceeds. This study monitors the change in the tensile and flexural properties of unidirectional prestressed glass fiber reinforced epoxy composites over a period of 12 months after manufacturing. The composites were prepared using three different fiber volume fractions 25%, 30%, and 40%. The results of mechanical testing showed that the prestressed composites acquired an initial increase up to 29% in the tensile properties and up to 32% in the flexural properties compared to the non-prestressed counterparts. Throughout the 12 months of study, the initial increase in both tensile and flexural strength showed a progressive reduction. The loss ratio of the initial increase was observed to be inversely proportional to the fiber volume fraction. For the prestressed composites fabricated with 25%, 30%, and 40% fiber volume fraction, the initial increase in tensile and flexural strength dropped by 29%, 25%, and 17%, respectively and by 34%, 26%, and 21%, respectively at the end of the study. Approximately 50% of the total loss took place over the first month after the manufacture, while after the sixth month, the reduction in mechanical properties became insignificant. Tensile modulus started to show a very slight reduction after the fourth/sixth month, while the flexural modulus reduction was observed from the beginning. Although the prestressed composites displayed time-dependent losses, their long-term mechanical properties still outperformed the non-prestressed counterparts.

Performance of Bamboo Fiber Reinforced Composites: Mechanical Properties

2021 ◽  
Vol 879 ◽  
pp. 284-293
Author(s):  
Norliana Bakar ◽  
Siew Choo Chin
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Vinyl Ester ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Bamboo Fiber ◽  
Synthetic Fiber ◽  
Fiber Reinforced ◽  
Fiber Volume ◽  
Volume Fractions

Fiber Reinforced Polymer (FRP) made from synthetic fiber had been widely used for strengthening of reinforced concrete (RC) structures in the past decades. Due to its high cost, detrimental to the environment and human health, natural fiber composites becoming the current alternatives towards a green and environmental friendly material. This paper presents an investigation on the mechanical properties of bamboo fiber reinforced composite (BFRC) with different types of resins. The BFRC specimens were prepared by hand lay-up method using epoxy and vinyl-ester resins. Bamboo fiber volume fractions, 30%, 35%, 40%, 45% and 50% was experimentally investigated by conducting tensile and flexural test, respectively. Results showed that the tensile and flexural strength of bamboo fiber reinforced epoxy composite (BFREC) was 63.2% greater than the bamboo fiber reinforced vinyl-ester composite (BFRVC). It was found that 45% of bamboo fiber volume fraction on BFREC exhibited the highest tensile strength compared to other BFRECs. Meanwhile, 40% bamboo fiber volume fraction of BFRVC showed the highest tensile strength between bamboo fiber volume fractions for BFRC using vinyl-ester resin. Studies showed that epoxy-based BFRC exhibited excellent results compared to the vinyl-ester-based composite. Further studies are required on using BFRC epoxy-based composite in various structural applications and strengthening purposes.

Mechanical Properties of Thermoplastic Composites via In Situ Polymerization from Cyclic Oligomers

2013 ◽  
Vol 750-752 ◽  
pp. 7-10
Author(s):  
Kou An Hao ◽  
Zhen Qing Wang ◽  
Li Min Zhou
Keyword(s):  
Mechanical Properties ◽  
In Situ Polymerization ◽  
High Viscosity ◽  
Thermoplastic Composites ◽  
Thermoplastic Matrix ◽  
Polymerization Catalyst ◽  
Short Beam ◽  
Beam Shear ◽  
Cyclic Oligomers

Fiber impregnation has been the main obstacle for thermoplastic matrix with high viscosity. This problem could be surmounted by adapting low viscous polymeric precursors Woven basalt fabric reinforced poly (butylenes terephthalate) composites were produced via in-situ polymerization at T=210°C. Before polymerization, catalyst was introduced to the reinforcement surface with different concentration. DSC is used to determine the polymerization and crystallization. SEM is used to detect whether the catalyst existed on surface. Both flexural and short-beam shear test are employed to study the corresponding mechanical properties.

Effects of Fiber Volume Fraction on Mechanical Properties of SiC-Fiber/Si3N4-Matrix Composites

1994 ◽  
Vol 77 (7) ◽  
pp. 1897-1900 ◽  
Author(s):  
Hockin H. K. Xu ◽  
Claudia P. Ostertag ◽  
Linda M. Braun ◽  
Isabel K. Lloyd
Keyword(s):  
Mechanical Properties ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Matrix Composites ◽  
Fiber Volume ◽  
Sic Fiber ◽  
Si3n4 Matrix

Biomimetic composites inspired by venous leaf

2017 ◽  
Vol 52 (3) ◽  
pp. 361-372 ◽  
Author(s):  
Gongdai Liu ◽  
R Ghosh ◽  
A Vaziri ◽  
A Hossieni ◽  
D Mousanezhad ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Yield Stress ◽  
Poisson’S Ratio ◽  
Composite Structures ◽  
Volume Fraction ◽  
Matrix Material ◽  
Poisson's Ratio ◽  
Fiber Volume ◽  
Young’S Moduli

A typical plant leaf can be idealized as a composite having three principal fibers: the central mid-fiber corresponding to the mid-rib, straight parallel secondary fibers attached to the mid-fiber representing the secondary veins, and then another set of parallel fibers emanating from the secondary fibers mimicking the tertiary fibers embedded in a matrix material. This paper introduces a biomimetic composite design inspired by the morphology of venous leafs and investigates the effects of venation morphologies on the in-plane mechanical properties of the biomimetic composites using finite element method. The mechanical properties such as Young’s moduli, Poisson’s ratio, and yield stress under uniaxial loading of the resultant composite structures was studied and the effect of different fiber architectures on these properties was investigated. To this end, two broad types of architectures were used both having similar central main fiber but differing in either having only secondary fibers or additional tertiary fibers. The fiber and matrix volume fractions were kept constant and a comparative parametric study was carried out by varying the inclination of the secondary fibers. The results show that the elastic modulus of composite in the direction of main fiber increases linearly with increasing the angle of the secondary fibers. Furthermore, the elastic modulus is enhanced if the secondary fibers are closed, which mimics composites with closed cellular fibers. In contrast, the elastic modulus of composites normal to the main fiber ( x direction) exponentially decreases with the increase of the angle of the secondary fibers and it is little affected by having secondary fibers closed. Similar results were obtained for the yield stress of the composites. The results also indicate that Poisson’s ratio linearly increases with the secondary fiber angle. The results also show that for a constant fiber volume fraction, addition of various tertiary fibers may not significantly enhance the mechanical properties of the composites. The mechanical properties of the composites are mainly dominated by the secondary fibers. Finally, a simple model was proposed to predict these behaviors.

Influence of fiber volume fraction and curing temperature on mechanical properties of jute/PLA green composites

2019 ◽  
Vol 28 (4) ◽  
pp. 273-284
Author(s):  
Jai Inder Preet Singh ◽  
Sehijpal Singh ◽  
Vikas Dhawan
Keyword(s):  
Mechanical Properties ◽  
Flexural Strength ◽  
Fiber Volume Fraction ◽  
Natural Fiber ◽  
Volume Fraction ◽  
Matrix Material ◽  
Research Work ◽  
Curing Temperature ◽  
Green Composites ◽  
Fiber Volume

Rising environmental concerns and depletion of petrochemical resources have resulted in an increased interest in biodegradable natural fiber-reinforced polymer composites. In this research work, jute fiber has been used as a reinforcement and polylactic acid (PLA) as the matrix material to develop jute/PLA green composites with the help of compression molding technique. The effect of fiber volume fraction ranging from 25% to 50% and curing temperature ranging from 160°C to 180°C on different samples were investigated for mechanical properties and water absorption. Results obtained from various tests indicate that with an increase in the fiber volume fraction, tensile and flexural strength increases till 30% fiber fraction, thereafter decreases with further increase in fiber content. Maximum tensile and flexural strength of jute/PLA composites was obtained with 30% fiber volume fraction at 160°C curing temperature. The trend obtained from mechanical properties is further justified through the study of surface morphology using scanning electron microscopy.

Porosity characterization and respective influence on short-beam strength of advanced composite processed by resin transfer molding and compression molding

2020 ◽  
pp. 096739112096845
Author(s):  
Ana Carolina Mendes Quintanilha Silva Santos ◽  
Francisco Maciel Monticeli ◽  
Heitor Ornaghi ◽  
Luis Felipe de Paula Santos ◽  
Maria Odila Hilário Cioffi
Keyword(s):  
Shear Strength ◽  
Mechanical Performance ◽  
Volume Fraction ◽  
Optimal Parameter ◽  
Resin Transfer Molding ◽  
Compression Molding ◽  
Viscous Force ◽  
Transfer Molding ◽  
Short Beam ◽  
Beam Shear

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.

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