scholarly journals High Temperature VARTM of Phenylethynyl Terminated Imides

2009 ◽  
Vol 21 (5) ◽  
pp. 653-672 ◽  
Author(s):  
Sayata Ghose ◽  
Kent A. Watson ◽  
Roberto J. Cano ◽  
Sean M. Britton ◽  
Brian J. Jensen ◽  
...  
Keyword(s):  
High Temperature ◽  
Composite Laminates ◽  
Thermal Cycle ◽  
Composite Structures ◽  
Void Content ◽  
High Porosity ◽  
Part Type ◽  
Transfer Molding ◽  
Aerospace Applications ◽  
Mass Spectroscopic Study

Depending on the part type and quantity, fabrication of composite structures using vacuum-assisted resin transfer molding (VARTM) can be more affordable than conventional autoclave techniques. Recent efforts have focused on adapting VARTM for the fabrication of high temperature composites. Due to their low melt viscosity and long melt stability, certain phenylethynyl terminated imides (PETI) can be processed into composites using high temperature VARTM (HT-VARTM). However, one of the disadvantages of the current HT-VARTM resin systems has been the high porosity of the resultant composites. For aerospace applications, the desired void fraction of less than 2% has not yet been achieved. In the current study, two PETI resins, LaRC PETI-330 and LaRC PETI-8 have been used to make test specimens using HT-VARTM. The resins were infused into ten layers of IM7-6K carbon fiber 5-harness satin fabric at 260 or 280 °C and cured at temperature up to 371 °C. Initial runs yielded composites with high void content, typically greater than 7% by weight. A thermogravimetric-mass spectroscopic study was conducted to determine the source of volatiles leading to high porosity. It was determined that under the thermal cycle used for laminate fabrication, the phenylethynyl endcap was undergoing degradation leading to volatile evolution. This finding was unexpected as high quality composite laminates have been fabricated under higher pressures using these resin systems. The amount of weight loss experienced during the thermal cycle was only about 1% by weight, but this led to a significant amount of volatiles in a closed system. By modifying the thermal cycle used in laminate fabrication, the void content was significantly reduced (typically ∼ 3% or less). The results of this work are presented herein.

Thermal cycle effects on laminated composite plates containing voids

2018 ◽  
Vol 53 (4) ◽  
pp. 489-501 ◽  
Author(s):  
Shambhu K Gupta ◽  
Mehdi Hojjati
Keyword(s):  
Shear Strength ◽  
Thermal Cycle ◽  
Composite Structures ◽  
Laminated Composite ◽  
Composite Plates ◽  
Interlaminar Shear Strength ◽  
Void Content ◽  
Manufacturing Method ◽  
Polished Cross Section ◽  
Interlaminar Shear

Composite structures are often cured in an autoclave to acquire the required space grade quality. Now the industry is focusing on the out of autoclave manufacturing method which leads to more voids inside laminate with respect to those manufactured in the autoclave. In the present work, the influence of voids on microcrack formation under thermal cycling and environmental conditions was analyzed. Thermal cycle experiments were performed using liquid nitrogen and oven, followed by microscopic observation of the polished cross-section of the 90° layered plies. Cracks were monitored, counted, and measured with respect to void and void free areas. Void content was characterized using microscopic and ImageJ software was used. It was observed that the microcracks will be formed both around the voids and in void free areas. As the number of thermal cycle increases, the number of microcrack around the voids increases much faster than compared to the void free areas. Also it was observed that most of microcracks were propagated in the transverse direction. Interlaminar shear strength was measured. Results indicate that interlaminar shear strength reduces as the number of cycle rises due to the increase in the microcrack density. Finite element method was used to simulate the process. The micro, meso, and macro model were created with respect to original samples voids and positions to calculate the stress distribution and its concentration. Good agreement between experiment and simulation was observed.

scholarly journals Isogeometric analysis for simulation of progressive damage in composite laminates

2018 ◽  
Vol 52 (25) ◽  
pp. 3471-3489 ◽  
Author(s):  
Marco S. Pigazzini ◽  
Yuri Bazilevs ◽  
Andrew Ellison ◽  
Hyonny Kim
Keyword(s):  
Composite Laminates ◽  
Isogeometric Analysis ◽  
Composite Structures ◽  
Low Velocity Impact ◽  
Stiffened Panel ◽  
Progressive Damage ◽  
Low Velocity ◽  
New Class ◽  
Aerospace Applications ◽  
Post Impact

The increasing popularity of composite materials in aerospace applications is creating the need for a new class of predictive methods and tools for the simulation of progressive damage in laminated fiber-reinforced composite structures. The unique challenges associated with modeling damage in these structures may be addressed by means of thin-shell formulations which are naturally developed in the context of Isogeometric Analysis. In this paper, we further validate our recently developed Isogeometric Analysis-based multi-layer shell model for progressive damage simulations using experimental data for low-velocity impact on a 24-ply flat panel. The validation includes a careful comparison of delamination and matrix damage patterns predicted by the Isogeometric Analysis-based simulation and those obtained from post-impact non-destructive evaluation of the damaged coupon. The Isogeometric Analysis-based formulation is then deployed on two additional examples: a stiffened panel and a full-scale UAV wing, to demonstrate its suitability for, and ease of application to, typical aerospace composite structures.

Applying Magnetic Consolidation Pressure During Cure to Improve Laminate Quality: A Comparative Analysis of Wet Lay-Up and Vacuum Assisted Resin Transfer Molding Processes

2017 ◽  
Author(s):  
Maya Pishvar ◽  
Mehrad Amirkhosravi ◽  
M. Cengiz Altan
Keyword(s):  
Composite Laminates ◽  
Permanent Magnets ◽  
Volume Fraction ◽  
Resin Transfer Molding ◽  
Void Content ◽  
Fiber Volume ◽  
Transfer Molding ◽  
Consolidation Pressure ◽  
A New Technique

This paper presents the application of a new technique, Magnet Assisted Composite Manufacturing (MACM), to enhance the quality of composite laminates fabricated by wet lay-up/vacuum bag (WLVB) and vacuum assisted resin transfer molding (VARTM). Towards this goal, a set of high-power, Neodymium permanent magnets, which are placed on a magnetic tool plate, is applied on the vacuum bag/lay-up. To further demonstrate the effectiveness of MACM, six-ply random mat, E-glass/epoxy composite laminates are produced under four processing scenarios: (i) Conventional WLVB; (ii) WLVB with magnetic consolidation; (iii) Conventional VARTM; and (iv) VARTM with magnetic consolidation. Applying magnetic consolidation pressure is found to be a convenient and efficient method for enhancing the overall quality of the laminates fabricated by WLVB and VARTM. For instance, in WLVB-MACM process, fiber volume fraction improves by 98% to 49% and void content reduces from 5% to less than 1.5% compared to conventional WLVB. These two factors lead to substantially increased mechanical properties of the WLVB-MACM laminates to a level comparable to those achieved by the higher-cost VARTM-MACM process.

TEM study of boron additions to cobalt aluminide

1988 ◽  
Vol 46 ◽  
pp. 546-547
Author(s):  
Gerald B. Feldewerth
Keyword(s):  
High Temperature ◽  
Turbine Engines ◽  
Major Drawback ◽  
University Of Missouri ◽  
Specific Strength ◽  
Aerospace Applications ◽  
Wide Range ◽  
Ordered Alloys ◽  
The University ◽  
Very High

In recent years an increasing emphasis has been placed on the study of high temperature intermetallic compounds for possible aerospace applications. One group of interest is the B2 aiuminides. This group of intermetaliics has a very high melting temperature, good high temperature, and excellent specific strength. These qualities make it a candidate for applications such as turbine engines. The B2 aiuminides exist over a wide range of compositions and also have a large solubility for third element substitutional additions, which may allow alloying additions to overcome their major drawback, their brittle nature.One B2 aluminide currently being studied is cobalt aluminide. Optical microscopy of CoAl alloys produced at the University of Missouri-Rolla showed a dramatic decrease in the grain size which affects the yield strength and flow stress of long range ordered alloys, and a change in the grain shape with the addition of 0.5 % boron.

ALCOA ALUMINUM ALLOY 7050

Alloy Digest ◽  
1990 ◽  
Vol 39 (1) ◽  
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
High Temperature ◽  
Magnesium Alloy ◽  
Stress Corrosion Cracking ◽  
Heat Treating ◽  
Thin Sections ◽  
Aerospace Applications ◽  
Temperature Performance ◽  
Aluminum Company

Abstract ALCOA ALUMINUM ALLOY 7050 is an aluminum-zinc-copper-magnesium alloy with a superior combination of strength, stress-corrosion cracking resistance and toughness, particularly in thick sections. In thin sections it also possesses an excellent combination of properties that are important for aerospace applications. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as creep. It also includes information on low and high temperature performance, and corrosion resistance as well as forming, heat treating, and joining. Filing Code: Al-233. Producer or source: Aluminum Company of America. Originally published as Aluminum 7050, January 1979, revised January 1990.

scholarly journals Superior Oxidation Resistance Titanium Alloy ARCONIC-THORTM for Aerospace Applications

2020 ◽  
Vol 321 ◽  
pp. 04013
Author(s):  
Sesh Tamirisakandala ◽  
Ernie Crist ◽  
Fusheng Sun ◽  
Matthew Dahar
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Oxidation Resistance ◽  
Cost Savings ◽  
Jet Engines ◽  
Aerospace Applications ◽  
Technology Advancement ◽  
Aerospace Systems ◽  
Material Systems ◽  
Nickel Base

Next generation fuel-efficient jet engines are running hotter presenting a structural challenge for the exhaust systems and structures adjacent to the engines. A conventional and affordable titanium alloy with superior oxidation resistance provides significant weight reductions and associated cost savings by eliminating the need for high density material systems such as nickel-base superalloys for service temperatures in between current titanium and nickel, enabling major technology advancement in high temperature aerospace applications. This paper presents an overview of Arconic’s engineered material ARCONIC-THORTM to address the needs of future aerospace systems.

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