scholarly journals The effect of processing on the microstructure of hoop-wound composite cylinders

2020 ◽  
Vol 54 (26) ◽  
pp. 3981-3997 ◽  
Author(s):  
Kaspar Lasn ◽  
Mats Mulelid
Keyword(s):  
Mechanical Performance ◽  
Pressure Vessels ◽  
Void Content ◽  
Cylinder Wall ◽  
Process Innovations ◽  
Short Beam ◽  
Beam Shear ◽  
Composite Microstructure ◽  
The Difference ◽  
Composite Cylinders

Fibre-reinforced polymer composites are increasingly used to make pipes and pressure vessels. The relationship between wet-winding manufacturing, composite microstructure, and the mechanical performance is complex due to many process parameters and material properties involved. Efficient manufacturing aspirations however drive process innovations that include new, radically different tow impregnation methods. In this work, the process–property–performance relationship is experimentally construed for hoop-wound carbon fibre/epoxy composite cylinders. The difference between cylinders produced by a new tow impregnation system and cylinders from the reference impregnation system was investigated. Winding speed and cylinder wall thickness were considered as two additional variables. The results indicate that, within current scope, composite microstructure is relatively insensitive to the winding speed and to final cylinder thickness. Meanwhile, un-optimized changes for tow impregnation affect the void content, the size distribution of voids and the interlaminar failure mode in short beam shear.

Fabrication and mechanical characterization of glass fibre reinforced triaxially braided composites

2020 ◽  
pp. 002199832094893
Author(s):  
Gayatri Vineela Marrivada ◽  
Phaneendra Kiran Chaganti ◽  
Ravindran Sujith
Keyword(s):  
Glass Fibre ◽  
Mechanical Characterization ◽  
Research Work ◽  
Braided Composites ◽  
Short Beam ◽  
Beam Shear ◽  
Glass Fibre Reinforced ◽  
The Difference ◽  
Experimental Values

The aim of this research work is to study the mechanical behaviour of dry triaxially braided glass fibre sleeves and its composites experimentally and analytically. The braided glass fibre sleeves for three angles 30°, 45° and 60° were fabricated on a modified maypole vertical braider following a regular braid architecture. Tensile, flexural, short beam shear and impact tests were performed to evaluate the mechanical properties of the composites. A numerical model was developed, which can be used to find the elastic properties and mechanical strength values of the dry braided fabric and its composites. It was observed that the tensile, flexural and interlaminar properties of 30° specimens were more compared to 45° and 60°. The difference between the estimated and experimental values were found to be an average of 8% for tensile moduli and 24% for the tensile strength.

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.

Development of novel high Tg polyimide-based composites. Part II: Mechanical characterisation

2017 ◽  
Vol 52 (2) ◽  
pp. 261-274 ◽  
Author(s):  
Spyros Tsampas ◽  
Patrik Fernberg ◽  
Roberts Joffe
Keyword(s):  
Elevated Temperature ◽  
Composite System ◽  
Mechanical Performance ◽  
Mechanical Tests ◽  
Basic Material ◽  
Mechanical Characterisation ◽  
Short Beam ◽  
Fibre Treatment ◽  
Beam Shear ◽  
Fibre Matrix

In this study, the mechanical performance assessment of a newly developed carbon fibre-reinforced polyimide composite system T650/NEXIMID® MHT-R is presented. This system was subjected to a series of mechanical tests at ambient and elevated temperature (320℃) to determine basic material properties. Moreover, an additional test was conducted, using a T650/NEXIMID® MHT-R laminate in which the fibre sizing was thermally removed prior to laminate manufacturing, to investigate the effect of fibre treatment on mechanical performance. The experimental results indicated that the T650/NEXIMID® MHT-R composites along with exceptionally high Tg (360–420℃) exhibited competitive mechanical properties to other commercially available polyimide and epoxy-based systems. At elevated temperature, the fibre-dominated properties were not affected whilst the properties defined by matrix and fibre/matrix interface were degraded by approximately 20–30%. Finally, the fibre sizing removal did not affect the tensile and compressive strength, however, the shear strength obtained from short-beam shear test was deteriorated by approximately 15%.

Detection of Voids in Carbon/Epoxy Laminates and Their Influence on Mechanical Properties

2017 ◽  
Vol 25 (5) ◽  
pp. 371-380 ◽  
Author(s):  
Luca Di Landro ◽  
Aurelio Montalto ◽  
Paolo Bettini ◽  
Stefania Guerra ◽  
Fabrizio Montagnoli ◽  
...  
Keyword(s):  
Composite Laminates ◽  
Mechanical Performance ◽  
Thermal Analyses ◽  
Void Content ◽  
Processing Conditions ◽  
Micro Computed Tomography ◽  
Sem Image ◽  
Beam Shear ◽  
Mechanical Performances ◽  
Curing Cycle

Defects, such as voids and delaminations, may significantly reduce the mechanical performance of components made of composite laminates. Distributed voids and porosity are generated during composite processing and are influenced by prepreg characteristics as well as by curing cycle parameters. On the basis of rheological and thermal analyses, as well as observations of laminates produced by different processing conditions, curing pressure appears the most influent factor affecting the void content. This work compares different methods for void analysis and quantitative evaluation (ultrasonic scan, micro-computed tomography, acid digestion, SEM image analysis) evidencing their applicative limitations. Carbon/epoxy laminates were produced in autoclave or oven by vacuum bag technique, using different processing conditions, so that void contents ranging from 0% to 7% volume were obtained. Effects of porosity over laminates mechanical performances are analysed. The results of tensile and compressive tests are discussed, considering the effect that different curing cycles have over void content as well as over fibre/resin fraction. Interlaminar strength, as measured by short beam shear tests, which is a matrix-dominated property, exhibits a reduction of failure strength up to 25% in laminates with the highest void content, compared to laminates with no porosity.

Effect of Ply Drop in Aerospace Composite Structures

2020 ◽  
Vol 847 ◽  
pp. 46-51
Author(s):  
Prakash Jadhav
Keyword(s):  
Composite Structures ◽  
Mechanical Performance ◽  
Laminated Composite ◽  
Carbon Composite ◽  
Thickness Variation ◽  
Element Analysis ◽  
Short Beam ◽  
Beam Shear ◽  
Carbon Composite Materials ◽  
Point Bend

In most of the aerospace laminated composite structures, thickness variation is achieved by introducing the ply drops at the appropriate locations. Ply drop means the resin rich regions created due to abrupt ending of individual plies within the set of plies. This research is focused on understanding and quantifying the effect of these ply drop regions on the mechanical performance of the aerospace composite structures. This is achieved here by designing the appropriate coupons (with and without ply drops) and analyzing them using finite element analysis. Some typical designs of coupons were manufactured using aerospace grade carbon composite materials, and then tested under four-point bend, cantilever and short beam shear tests to check and validate the effect that was seen in the analysis. It is concluded here that allowable failure strains are different for with and without ply drop cases by a significant amount.

Mechanical Performance of Carbon/Epoxy Composites with Embedded Polymeric Films

2007 ◽  
Vol 334-335 ◽  
pp. 469-472 ◽  
Author(s):  
Ben Qi ◽  
Michael Bannister
Keyword(s):  
Composite Laminates ◽  
Mechanical Performance ◽  
Polymeric Films ◽  
Epoxy Composites ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Lap Shear ◽  
Short Beam ◽  
Monitoring Applications ◽  
Beam Shear

This paper presents experimental results on the mechanical performance of advanced carbon/epoxy composites with embedded polymeric films. The composite laminates with polymeric films, which are potentially used as a sensor/actuator carrier for structural health monitoring applications, were investigated under various mechanical loadings including low velocity impact, single lap shear and short beam shear. The preliminary work showed that embedment of those polymeric films does not degrade, but could significantly improve, the mechanical properties of the composite laminates.

Investigation of various techniques for controlled void formation in fiberglass/epoxy composites

2020 ◽  
pp. 002199832095251
Author(s):  
Donald Klosterman ◽  
Charles Browning ◽  
Issa Hakim ◽  
Kyle Lach
Keyword(s):  
Void Formation ◽  
Void Content ◽  
Carbon Fiber Composites ◽  
Residual Water ◽  
Building Structures ◽  
Failure Initiation ◽  
Spray Method ◽  
Short Beam ◽  
Burn Out ◽  
Beam Shear

The effect of porosity in composite materials has been studied for years due to its deleterious effects on mechanical properties, especially matrix dominated properties. Currently there is an increasing use of composites in infrastructure worldwide, for example bridge components, residential and building structures, marine structures such as piers and docks, and large industrial chemical tanks. Most of these applications use fiberglass composites. Unfortunately, most of the published literature has focused on carbon fiber composites, in which fiber diameter and gas-fiber interactions are different than fiberglass composites. Therefore, the present study was undertaken to revisit the effect of porosity but specifically in fiberglass composites. The goal of this experimental study was to implement and evaluate various methods for creating porosity in fiberglass composites in a controlled manner in terms of obtaining repeatable void content, morphology, and location within the laminate. The various methods included using different amounts of autoclave pressure, adding a small amount of water between prepreg layers, and using dry fabric layers to starve the laminate of resin. Ultrasonic C-scan nondestructive evaluation was used to assess the quality of the cured panels, as well as optical and electron microscopy and void content measurements via resin burn-out. The cured panels were mechanically tested using the short beam shear (SBS) method. The results showed that the water spray method proved to be the best in terms of producing noticeably different levels of porosity, although the panels required drying to remove residual water after cure. The voids from all three techniques were either oval or elongated in-plane between the plies, but they were not uniformly distributed in-plane. The use of C-scan proved to be helpful for characterizing overall uniformity of each panel, although the results could not be used to directly compare void content between panels. The use of SBS testing was successful for evaluating void dominated properties in panels with high void content, although it was not very sensitive to coupons with lower void contents. Several interesting observations are offered in this manuscript of the fracture surface details and their relation to the SBS load deflection curves. Overall, it was found that the failure mechanisms were mixed mode and the voids did not serve as failure initiation sites. However, the voids participated mainly in the horizontal propagation of cracks between layers, presumably making it easier when they were intersected by a crack and reducing SBS strength.

scholarly journals Simultaneous effects of rice husk silica and silicon carbide whiskers on the mechanical properties and morphology of sodium geopolymer

2020 ◽  
Vol 54 (29) ◽  
pp. 4611-4620 ◽  
Author(s):  
Akm Samsur Rahman ◽  
Chirag Shah ◽  
Nikhil Gupta
Keyword(s):  
Silicon Carbide ◽  
Compressive Strength ◽  
Flexural Strength ◽  
Silica Nanoparticles ◽  
Rice Husk ◽  
Silicon Carbide Whiskers ◽  
Short Beam ◽  
Spherical Silica ◽  
Beam Shear ◽  
Strength Improvement

The current research is focused on developing a geopolymer binder using rice husk ash–derived silica nanoparticles. Four types of rice husks were collected directly from various rice fields of Bangladesh in order to evaluate the pozzolanic activity and compatibility of the derived rice husk ashes with precursors of sodium-based geopolymers. Silicon carbide whiskers were introduced into sodium-based geopolymers in order to evaluate the response of silicon carbide whiskers to the interfacial bonding and strength of sodium-based geopolymers along with rice husk ashes. Compression, flexural and short beam shear tests were performed to investigate the synergistic effect of rice husk ashes–derived silica and commercially available silicon carbide whiskers. Results show that rice husk ashes–derived spherical silica nanoparticles reduced nano-porosity of the geopolymers by ∼20% and doubled the compressive strength. The simultaneous additions of rice husk ashes and silicon carbide whiskers resulted in flexural strength improvement by ∼27% and ∼97%, respectively. The increase in compressive strength due to the inclusion of silica nanoparticles is related to the reduction in porosity. The increase in flexural strength due to simultaneous inclusion of silica and silicon carbide whiskers suggest that silica particles are compatible with the metakaolin-based geopolymers, which is effective in consolidation. Finally, microscopy suggest that silicon carbide whiskers are effective in increasing bridged network and crack resistance.

Strength Loss in Composite Cylinders Under Impact

1988 ◽  
Vol 110 (2) ◽  
pp. 180-184 ◽  
Author(s):  
A. P. Christoforou ◽  
S. R. Swanson
Keyword(s):  
Composite Structures ◽  
Composite Plates ◽  
Strength Loss ◽  
Pressure Vessels ◽  
Fourier Series Expansion ◽  
Lateral Impact ◽  
Low Velocity ◽  
Expansion Procedure ◽  
The Impact ◽  
Composite Cylinders

The problem of strength loss in composite structures due to impact appears to be important due to the sensitivity of advanced composites to these loadings. Although a number of studies have been carried out on impact of flat composite plates, relatively little work has been done on tubular geometries such as pressure vessels despite the usage in applications. We have addressed the problem of calculating strength loss due to low velocity, lateral impact of composite cylinders. In our model we use an existing Fourier Series expansion procedure to calculate ply stresses and strains, compare these values with allowables to predict fiber breakage during the impact, and finally use fracture mechanics to predict the strength loss due to the impact. Although the model is quite simplified, the general trends of experiments appear to be represented.

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