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

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%.

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

Journal of Composite Materials ◽

10.1177/0021998320923139 ◽

2020 ◽

Vol 54 (26) ◽

pp. 3981-3997 ◽

Cited By ~ 1

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.

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

Polymers and Polymer Composites ◽

10.1177/0967391120968452 ◽

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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Assessment of mechanical strength of nano silica concrete (NSC) subjected to elevated temperatures

Journal of Structural Fire Engineering ◽

10.1108/jsfe-10-2017-0041 ◽

2019 ◽

Vol 10 (1) ◽

pp. 90-109 ◽

Cited By ~ 4

Author(s):

Hala Mohamed Elkady ◽

Ahmed M. Yasien ◽

Mohamed S. Elfeky ◽

Mohamed E. Serag

Keyword(s):

Elevated Temperature ◽

Bond Strength ◽

Elevated Temperatures ◽

Mechanical Performance ◽

Mechanical Tests ◽

Nano Silica ◽

Content Type ◽

Post Exposure ◽

Concrete Mix ◽

Bond Strengths

Purpose This paper aims to inspect the effect of indirect elevated temperature on the mechanical performance of nano silica concrete (NSC). The effect on both compressive and bond strengths is studied. Pre- and post-exposure to elevated temperature ranges of 200 to 600°C is examined. A range covered by three percentages of 1.5, 3 and 4.5 per cent nano silica (NS) in concrete mixes is tested. Design/methodology/approach Pre-exposure mechanical tests (normal conditions – room temperature), using 3 per cent NS in the concrete mix, led to the highest increase in both compressive and bond strengths (43 per cent and 38.5 per cent, respectively), compared to the control mix without NS (based on 28-day results). It is worth noticing that adding NS to the concrete mixes does not have a significant effect on improving early-age strength. Besides, permeability tests are performed on NSC with different NS ratios. NS improved the concrete permeability for all tested percentages of NS. The maximum reduction is accompanied by the maximum percentage used (4.5 per cent NS in the NSC mix), reducing permeability to half the value of the concrete mix without NS. As for post-exposure to elevated-temperature mechanical tests, NSC with 1.5 per cent NS exhibited the lowest loss in strength owing to indirect heat exposure of 600°C; the residual compressive and bond strengths are 73 per cent and 35 per cent, respectively. Findings The dispersion technique of NS has a key role in NSC-distinguished mechanical performance with NSC having lower NS percentages. NS significantly improved bond strength. NS has a remarkable effect on elevated temperature endurance. The bond strength of NSC exposed to elevated temperatures suffered faster deterioration than compressive strength of the exposed NSC. Research limitations/implications A special scale factor needs to be investigated for the NSC. Originality/value Although a lot of effort is placed in evaluating the benefits of using nano materials in structural concrete, this paper presents one of the first outcomes of the thermal effects on concrete mixes with NS as a partial cement replacement.

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Effect of Ply Drop in Aerospace Composite Structures

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.847.46 ◽

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.

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Damage Evaluation of GLARE®4B under Interlaminar Shear Loading at Different Temperature Conditions

Advanced Composites Letters ◽

10.1177/096369350501400201 ◽

2005 ◽

Vol 14 (2) ◽

pp. 096369350501400 ◽

Cited By ~ 9

Author(s):

Stephan Hinz ◽

Jens Heidemann ◽

Karl Schulte

Keyword(s):

Shear Stiffness ◽

Shear Loading ◽

Multiple Cracks ◽

Interface Failure ◽

Short Beam ◽

Beam Shear ◽

Interlaminar Shear ◽

Observed Damage ◽

Increasing Temperature ◽

Fibre Matrix

The fibre reinforced metal laminate GLARE®4B was investigated under interlaminar shear loading conditions at temperatures between −50°C and 110°C. Short beam shear (ILSS) and double notched shear (DNS) tests were performed. The interlaminar shear strength decreases strongly with increasing temperature. The DNS test shows that the shear strain increases and the interlaminar shear stiffness decreases with increasing temperature. The observed damage occurs mainly in the 90°-fibre layer. For low temperatures delamination between the fibre-layers is the dominant failure mode. The higher the temperature, the more cracks develop in the 90°-layers. These multiple cracks coalesce with increasing shear load and form the final fracture surface. Light and scanning electron microscopy showed that the cracks are mainly based on fibre-matrix interface failure.

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Mechanical Performance of Carbon/Epoxy Composites with Embedded Polymeric Films

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.334-335.469 ◽

2007 ◽

Vol 334-335 ◽

pp. 469-472 ◽

Cited By ~ 1

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.

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Effects of Interphase and Fibre Content on the Mechanical Behavior of Weft-Knitted Glass Fibre Reinforced Polypropylene

Advanced Composites Letters ◽

10.1177/096369359700600201 ◽

1997 ◽

Vol 6 (2) ◽

pp. 096369359700600 ◽

Cited By ~ 2

Author(s):

J. Karger-Kocsis ◽

E. Moos ◽

T. Czigány

Keyword(s):

Mechanical Performance ◽

Mechanical Tests ◽

Fibre Content ◽

Matrix Adhesion ◽

Loading Mode ◽

Static Tensile ◽

Glass Fibre Reinforced ◽

Flexural Tests ◽

Commingled Yarns ◽

Fibre Matrix

The mechanical performance of weft knitted glass fiber (GF) fabric-reinforced polypropylene (PP) composite sheets produced by hot pressing of stacked knit layers was investigated. The knits were built-up of commingled yarns showing extremely different fibre/matrix adhesion. The GF content of the commingled yarns was 50 (≍ 26 vol.%) and 70 wt.% (≍45 vol.%), respectively. The effects of fibre/matrix adhesion and fibre content were characterized by dynamic-mechanical thermoanalysis (DMTA), static tensile and flexural tests in both course (C) and wale (W) direction of the knit. In addition, the sheets were subjected to instrumented falling weight perforation impact (IFWI). It was found that the knit structure-related stiffness anisotropy depended on the loading mode of the composites. The detrimental effect of the poor adhesion between GF and PP was well reflected in all mechanical tests conducted.

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Insight into the Mechanical Performance of the UHPC Repaired Cementitious Composite System after Exposure to High Temperatures

Materials ◽

10.3390/ma14154095 ◽

2021 ◽

Vol 14 (15) ◽

pp. 4095

Author(s):

Qing Chen ◽

Zhiyuan Zhu ◽

Rui Ma ◽

Zhengwu Jiang ◽

Yao Zhang ◽

...

Keyword(s):

Compressive Strength ◽

High Temperature ◽

High Temperatures ◽

Bonding Strength ◽

Composite System ◽

Mechanical Performance ◽

High Performance Concrete ◽

Interfacial Structure ◽

Cementitious Composite ◽

Average Percentage

In this paper, the mechanical performance of an ultra-high-performance concrete (UHPC) repaired cementitious composite system, including the old matrix and the new reinforcement (UHPC), under various high temperature levels (20 °C, 100 °C, 300 °C, and 500 °C) was studied. In this system, UHPC reinforced with different contents of steel fibers and polypropylene (PP) fibers was utilized. Moreover, the physical, compressive, bonding, and flexural behaviors of the UHPC repaired system after being exposed to different high temperatures were investigated. Meanwhile, X-ray diffraction (XRD), baseline evaluation test (BET), and scanning electron microscope (SEM) tests were conducted to analyze the effect of high temperature on the microstructural changes in a UHPC repaired cementitious composite system. Results indicate that the appearance of the bonded system changed, and its mass decreased slightly. The average percentage of residual mass of the system was 99.5%, 96%, and 94–95% at 100 °C, 300 °C, and 500 °C, respectively. The residual compressive strength, bonding strength, and flexural performance improved first and then deteriorated with the increase of temperature. When the temperature reached 500 °C, the compressive strength, bonding strength, and flexural strength decreased by about 20%, 30%, and 15% for the UHPC bonded system, respectively. Under high temperature, the original components of UHPC decreased and the pore structure deteriorated. The cumulative pore volume at 500 °C could reach more than three times that at room temperature (about 20 °C). The bonding showed obvious deterioration, and the interfacial structure became looser after exposure to high temperature.

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Preparation and Performance Evaluation of Duotone 3D-Printed Polyetheretherketone as Oral Prosthetic Materials: A Proof-of-Concept Study

Polymers ◽

10.3390/polym13121949 ◽

2021 ◽

Vol 13 (12) ◽

pp. 1949

Author(s):

Ling Ding ◽

Wei Lu ◽

Jiaqi Zhang ◽

Chuncheng Yang ◽

Guofeng Wu

Keyword(s):

Titanium Dioxide ◽

Performance Evaluation ◽

Mechanical Performance ◽

Mechanical Tests ◽

Flexural Properties ◽

Proof Of Concept ◽

Tooth Color ◽

Dental Application ◽

3D Printed ◽

And Performance

Literature has reported the successful use of 3D printed polyetheretherketone (PEEK) to fabricate human body implants and oral prostheses. However, the current 3D printed PEEK (brown color) cannot mimic the vivid color of oral tissues and thus cannot meet the esthetical need for dental application. Therefore, titanium dioxide (TiO2) and ferric oxide (Fe2O3) were incorporated into PEEK to prepare a series of tooth-color and gingival-color PEEK composites in this study. Through color measurements and mechanical tests, the color value and mechanical performance of the 3D printed PEEK composites were evaluated. In addition, duotone PEEK specimens were printed by a double nozzle with an interface between tooth-color and gingival-color parts. The mechanical performance of duotone PEEK with two different interfaces (horizontal and vertical) was investigated. With the addition of TiO2 and Fe2O3, the colors of 3D printed PEEK composites become closer to that of dental shade guides. 3D printed PEEK composites generally demonstrated superior tensile and flexural properties and hence have great potential in the dental application. In addition, duotone 3D printed PEEK with a horizontal interfacial orientation presented better mechanical performance than that with a vertical one.

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