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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Short RNA indicator sequences are not completely degraded by autoclaving

Short indicator RNA sequences (,100 bp) persist after autoclaving and are recovered intact by molecular amplification. Primers targeting longer sequences are most likely to produce false positives due to amplification errors easily verified by melting curves analyses. If short indicator RNA sequences are used for virus identification and quantification then post autoclave RNA degradation methodology should be employed, which may include further autoclaving.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Re-establishment of Sandia National Labs super-critical carbon dioxide testing autoclave capability for exposure of metal alloys and polymers (Level 4 Milestone Report)

The sCO 2 system located in 916/160A, Sandia National Laboratories, CA, was constructed in 2014, for testing of materials in the presence of supercritical carbon dioxide (sCO 2 ) at high pressures (up to 3500 psi) and temperatures (up to 650°C). The basic design of the system consists of a thermally insulated IN625 autoclave, a high-pressure supercritical CO 2 compressor, autoclave heaters, temperature controllers, gas manifold, and temperature and pressure diagnostics. This system was modified in 2016 (sCO 2 compressor was removed) to enable corrosion studies with metal alloys in gaseous CO 2 at lower pressure (up to 300 psi) at 500°C. The capability was not used much afterwards until 2020, when preliminary tests using this capability (again without the supercritical CO 2 compressor) involved the exposure of fatigue and tensile specimens of HN 230 and 800H alloys to CO 2 gas for 168 hours in gaseous CO 2 . Using this capability, we finished experiments with low pressure (450 psi/ 3 MPa), high temperature (650°C) exposure of fatigue and tensile specimens of HN 230 and 800H alloys to CO 2 gas for 168 hours. The data from these experiments will be compared to that gathered from experiments performed in 2020 using the tube furnace and presented in a future report. It is to be noted that the tube furnace experiments ran 500-1500 hours, unlike the 168 hours of exposure in the recent experiment. This can help validate the use of the sCO 2 autoclave for both CO 2 and sCO 2 experiments.

36 MATERIALS SCIENCE↗
NASA NTRS1974

Development of autoclavable polyimides

A poly(Diels-Alder) (PDA) resin approach was investigated as a means to achieve autoclavability of high temperature resistant resin/fiber composites under mild fabrication procedures. Low void content Type A-S graphite reinforced composites were autoclave fabricated from a PDA resin/fiber prepared from an acetone:methanol:dioxane varnish. Autoclave conditions were 477K (400F) and 0.7 MN/sq m (100 psi) for up to two hours duration. After postcure at temperatures up to 589K (600F), the composites demonstrated high initial mechanical properties at temperatures up to 561K (550F). The results from isothermal aging studies in air for 1000 hours indicated potential for long-term ( 1000 hours) use at 533K (500F) and shorter-term (up to 1000 hours) at 561K (550F).

Orell, M. K.↗
NASA NTRS1985

Properties of autoclaved Gr/PI composites made from improved tack PMR-15 prepreg

Autoclave processing studies were conducted, using improved tack PMR-15 prepreg, to determine the effect of tack enhancing PMR resin modifications on composite processability and mechanical properties. Improved tack graphite fiber reinforced PMR-15 prepregs were prepared and exposed to ambient conditions for various times and then autoclave molded into composites. Composite specimens were prepared and tested for flexural and interlaminar shear strengths at room temperature and 316 C. The retention of flexural and interlaminar shear strength as a function of exposure in air at 316 C was also determined. The results show that the modified PMR resin solutions provide prepreg with improved tack and drape retention characteristics without adversely affecting processability or mechanical properties of autoclave molded graphite fiber reinforced PMR-15 composites.

Vannucci, R. D.↗
NASA NTRS2012

Mechanical Characterization of In and Out-of-Autoclave Cured Composite Panels for Large Launch Vehicles

Two manufacturing demonstration panels (1/16th-arc-segments of 10 m diameter cylinder) were fabricated under the composites part of the Lightweight Space Structures and Materials program. Both panels were of sandwich construction with aluminum core and 8-ply quasi-isotropic graphite/epoxy facesheets. One of the panels was constructed with in-autoclave curable unidirectional prepreg (IM7/977-3) and the second with out-of-autoclave unidirectional prepreg (T40-800B/5320-1). Following NDE inspection, each panel was divided into a number of small specimens for material property characterization and a large (0.914 m wide by 1.524 m long) panel for a buckling study. Results from the small specimen tests were used to (a) assess the fabrication quality of each 1/16th arc segment panel and (b) to develop and/or verify basic material property inputs to Finite Element analysis models. The mechanical performance of the two material systems is assessed at the coupon level by comparing average measured properties such as flatwise tension, edgewise compression, and facesheet tension. The buckling response of the 0.914 m wide by 1.524 m long panel provided a comparison between the in- and out-of autoclave systems at a larger scale.

Kellas, Sotiris↗
NASA NTRS2013

Out of the Autoclave Fabrication of LaRC[TradeMark] PETI-9 Polyimide Laminates

The NASA Langley Research Center developed polyimide system, LaRC PETI-9, has successfully been processed into composites by high temperature vacuum assisted resin transfer molding (HT-VARTM). To extend the application of this high use temperature material to other out-of-autoclave (OOA) processing techniques, the fabrication of PETI- 9 laminates was evaluated using only a vacuum bag and oven cure. A LaRC PETI-9 polyimide solution in NMP was prepared and successfully utilized to fabricate unidirectional IM7 carbon fiber prepreg that was subsequently processed into composites with a vacuum bag and oven cure OOA process. Composite panels of good quality were successfully fabricated and mechanically tested. Processing characteristics, composite panel quality and mechanical properties are presented in this work. The resultant properties are compared to previously developed LaRC material systems processed by both autoclave and OOA techniques including the well characterized, autoclave processed LaRC PETI-5.

Cano, Robert J.↗
NASA NTRS2015

Failure Predictions of Out-of-Autoclave Sandwich Joints with Delaminations under Flexure Loads

An analysis and a test program was conducted to investigate the damage tolerance of composite sandwich joints. The joints contained a single circular delamination between the face-sheet and the doubler. The coupons were fabricated through out-of-autoclave (OOA) processes, a technology NASA is investigating for joining large composite sections. The four-point bend flexure test was used to induce compression loading into the side of the joint where the delamination was placed. The compression side was chosen since it tends to be one of the most critical loads in launch vehicles. Autoclave cure was used to manufacture the composite sandwich sections, while the doubler was co-bonded onto the sandwich face-sheet using an OOA process after sandwich panels were cured. A building block approach was adopted to characterize the mechanical properties of the joint material, including the fracture toughness between the doubler and facesheet. Twelve four-point-bend samples were tested, six in the sandwich core ribbon orientation and six in sandwich core cross-ribbon direction. Analysis predicted failure initiation and propagation at the pre-delaminated location, consistent with experimental observations. A building block approach using fracture analyses methods predicted failure loads in close agreement with tests. This investigation demonstrated a small strength reduction due to a flaw of significant size compared to the width of the sample. Therefore, concerns of bonding an OOA material to an in-autoclave material was mitigated for the geometries, materials, and load configurations considered.

Damage↗
NASA NTRS2015

Failure Predictions of Out-of-Autoclave Sandwich Joints with Delaminations Under Flexure Loads

An analysis and a test program was conducted to investigate the damage tolerance of composite sandwich joints. The joints contained a single circular delamination between the face-sheet and the doubler. The coupons were fabricated through out-of-autoclave (OOA) processes, a technology NASA is investigating for joining large composite sections. The four-point bend flexure test was used to induce compression loading into the side of the joint where the delamination was placed. The compression side was chosen since it tends to be one of the most critical loads in launch vehicles. Autoclave cure was used to manufacture the composite sandwich sections, while the doubler was co-bonded onto the sandwich face-sheet using an OOA process after sandwich panels were cured. A building block approach was adopted to characterize the mechanical properties of the joint material, including the fracture toughness between the doubler and face-sheet. Twelve four-point-bend samples were tested, six in the sandwich core ribbon orientation and six in sandwich core cross-ribbon direction. Analysis predicted failure initiation and propagation at the pre-delaminated location, consistent with experimental observations. Fracture analyses methods predicted failure loads in close agreement with tests. This investigation demonstrated a strength reduction of 10 percent due to a flaw of significant size compared to the width of the sample. Therefore, concerns of bonding an OOA material to an in-autoclave material was mitigated for the geometries, materials, and load configurations considered.

Tolerance↗
NASA NTRS2015

Failure Predictions of Out-of-Autoclave Sandwich Joints with Delaminations Under Flexure Loads

An analysis and a test program was conducted to investigate the damage tolerance of composite sandwich joints. The joints contained a single circular delamination between the face-sheet and the doubler. The coupons were fabricated through out-of-autoclave (OOA) processes, a technology NASA is investigating for joining large composite sections. The four-point bend flexure test was used to induce compression loading into the side of the joint where the delamination was placed. The compression side was chosen since it tends to be one of the most critical loads in launch vehicles. Autoclave cure was used to manufacture the composite sandwich sections, while the doubler was co-bonded onto the sandwich face-sheet using an OOA process after sandwich panels were cured. A building block approach was adopted to characterize the mechanical properties of the joint material, including the fracture toughness between the doubler and face-sheet. Twelve four-point-bend samples were tested, six in the sandwich core ribbon orientation and six in sandwich core cross-ribbon direction. Analysis predicted failure initiation and propagation at the pre-delaminated location, consistent with experimental observations. A building block approach using fracture analyses methods predicted failure loads in close agreement with tests. This investigation demonstrated a small strength reduction due to a flaw of significant size compared to the width of the sample. Therefore, concerns of bonding an OOA material to an in-autoclave material was mitigated for the geometries, materials, and load configurations considered.

Tolerance↗
NASA NTRSDate not supplied

In-Situ Detection of Process-Induced Porosity During Cure of Out-of-Autoclave Composites

Composite materials offer unique benefits in aerospace applications, including high strength-to-weight ratio, and are becoming increasingly used by industry manufacturers. Current manufacturing and processing methods can lead to defects in the composites, which are identified after fabrication using inspection methods. This study utilized a high-temperature ultrasonic inspection system to detect process-induced porosity in an out-of-autoclave (OOA) composite panel during cure. In order to perform ultrasonic scans in-situ during cure, the system needed to be able to operate at oven temperatures up to 200 °C. There are no commercially available ultrasonic scanning systems that can operate continuously at these temperatures, so an enclosure was fabricated to insulate the ultrasonic system in the curing oven. The enclosure housed a MISTRAS® motorized X-Y raster scanner and contact transducer (Olympus® X2002). The Olympus® X2002 contact transducer is a continuous high-temperature delay line transducer with a center frequency of 2.25 MHz. In order to prevent the inside of the enclosure from reaching high temperatures, a sparge pipe inside the cooling enclosure was connected to a liquid nitrogen (LN2) tank outside of the oven via insulated hoses. The cooling system was automatically controlled by a temperature controller that was programmed to open a solenoid valve along the hose at 31 ℃ and close at 28 ℃ inside the cooling enclosure. When the solenoid valve was open, LN2 would flow from the LN2 tank and vaporize prior to reaching cooling enclosure. A U-shaped sparge pipe had holes drilled along its length to uniformly introduce cold nitrogen gas into the cooling enclosure. This prevented the motors from ever reaching the maximum desired operating temperature of 38 ℃. In the bottom of the enclosure, the tool plate was placed with the composite facing the outside of the enclosure, exposing it to the temperatures of the oven. The tool plate was 63.5 mm thick borosilicate glass, which was chosen for its low ultrasonic attenuation and moderate thermal conductivity. A thin layer of ultrasonic couplant was placed on the tool plate. The transducer sent and received ultrasonic waves through the tool plate into the composite. A MISTRAS® Remote UT System performed all wave generation, analog to digital conversion, and data acquisition and processing. The transducer was connected directly to the Remote UT System via a high-temperature BNC cable (CD International, RG-316). Polyimide insulated copper wire was used to connect the scanner to a 2-axis motor drive, which was connected to the Remote UT System. The motor drive and Remote UT System were located outside the industrial oven. A diagram of the ultrasonic system is shown in Figure 1. Figure 1: Diagram of ultrasonic in-situ defect detection system. In this study, a porosity gradient was introduced into the carbon fiber reinforced polymer (CFRP) composite through a misfit of the part and caul plate. A 24-ply quasi-isotropic ([0/90, ±45]12S) composite panel was laid up using Newport® AS4C-M/NB321 out-of-autoclave (OOA) plain weave (PW) prepreg (42% resin content, 195 g/m2). The first 16 plies were 203 mm × 203 mm. Ply drops were incorporated into the panel by decreasing the length of plies 17-24. The sizes of each ply are included in Table 1. All plies were centered along their length (x-axis) creating a trapezoidal type cross-section. Table 1: Ply sizes Plies Length (mm) Width (mm) 1-16 203 203 17-18 102 203 19-20 85 203 21-22 68 203 23-24 51 203 A 15-5 stainless steel caul plate (Size: 203 × 203 × 1.2 mm) was placed on the laminate. The composite and caul plate were vacuum bagged to the tool plate. Per the product datasheet, Newport 321 can be cured between 121 °C and 149 °C, depending on service temperature, with a hold for 90-120 minutes. Based on prior thermal testing of the cooling enclosure, the desired composite temperature cycle could be attained when the air temperature of the oven was ramped to 160 °C at a rate of 1.7 °C/min with a 3 hour hold. The extended hold was not necessary to cure the composite, but did allow for additional scans at the cure temperature during preliminary testing. The composite panel was under vacuum pressure for the entire cure cycle. Under vacuum, the caul plate deformed causing high and low pressure regions. The low-pressure regions formed high porosity in the composite part. The ultrasonic data collected showed that the inspection system was able to monitor the evolution of porosity within the composite throughout the cure cycle. Fifty scans of a 203 mm × 51 mm (8 in. × 2 in.) area of the composite were completed throughout the cure cycle. The scan speed was set to 43 mm/s in the x-direction and 36 mm/s in the y-direction, with a 1.0 mm/pixel resolution in both directions. Each scan took approximately five minutes to complete. Figure 2 shows C-scan amplitude data (top view) from one scan during the cure cycle. The color map indicates the maximum amplitude (%) measured with a time gate that contains reflections from the back surface (furthest from the transducer in contact with the caul plate) of the composite. Because porosity in the composite increases the ultrasonic attenuation in the composite part, a higher amplitude (red) indicates low porosity and a lower amplitude (blue) indicates high porosity. The regions where the caul plate was applying increased pressure (center and ends of the panel) resulted in reduced porosity, whereas the ply drop regions had reduced pressure and thus had higher porosity. Figure 2: Amplitude C-scan (top view) of OOA composite from one scan during the 160 °C temperature hold. Higher amplitude (red) indicates low porosity. Lower amplitude (blue) indicates high porosity. A B-scan is a two-dimensional image plotting the ultrasonic signals from a single y-position at every x-location of the composite panel. The travel time (μs) of the ultrasonic wave (representing the through-thickness location) is plotted along the y-axis, and the ultrasonic wave signal is represented as a contour map. Based on the B-scan data, the location of the defects with respect to the composite thickness was able to be determined. The ply drop regions had high porosity near the front (tool plate) surface of the composite (Figure 3). Figure 3: B-scan (cross-section view) of OOA composite from one scan during the 160 °C temperature hold. Using the data obtained from amplitude C-scans and B-scans throughout the cure cycle, the high and low porosity regions within the composite laminate were detected and localized with high spatial resolution. This paper will discuss the evolution of porosity content in the OOA composite during cure. OOA tests aided the transition of this system to an autoclave, which is the primary method of curing aerospace-grade thermoset composites.

Tyler B. Hudson↗
NASA NTRS2021

Porosity Detection and Localization During Composite Cure Inside an Autoclave Using Ultrasonic Inspection

Composite materials offer unique benefits in aerospace applications such as increased strength-to-weight ratio and improved fatigue properties. They are increasingly being used in major commercial aircraft programs. However, current processing methods can lead to defects in composite parts, which must be detected using post-manufacturing inspection methods. Porosity (i.e., pores, voids) is a critical defect from the cure process that is detrimental to performance of the composite part. It is therefore necessary to understand and eliminate the formation of porosity defects. At NASA Langley Research Center, an in-situ cure monitoring system was developed to detect porosity defects as they form in real-time inside an autoclave. A capability to directly detect and localize porosity within a composite during cure did not exist before. This study is focused on an elevated-temperature ultrasonic inspection system to detect porosity defects in composites during autoclave cure. The ultrasonic inspection system operated inside an autoclave within an enclosure cooled by intermittent liquid nitrogen (LN_2) injections. A high-temperature, 2.25 MHz, transducer transmitted ultrasonic waves through the tool plate and into the composite part and measured the amplitude and time of flight of the reflected waves with a 1 mm × 1 mm step size/areal resolution. Porosity was observed via the ultrasonic reflections, which experienced increased attenuation in regions of high porosity. Distinct regions of increased porosity were present due to uneven pressure across the panel, which was driven by an intentional misfit between the flat caul plate and the tapered composite panel with ply drops. The results were validated by post-cure ultrasonic inspection and micrographs. The in-situ inspection system was able to successfully provide porosity detection and localization in the tapered ply-drop panel. The successful results indicate the promise of this system for future implementation in the manufacturing of composite structures for aerospace applications.

Composites↗
NASA NTRS2025

Improving Adhesive Bondline Time of Flight Predictions During Autoclave Cure Utilizing Machine Learning

Composite materials are increasingly being used in aerospace applications due to their superior strength-to-weight ratio compared to commonly used metals. A current limitation to widespread adoption is the certification of adhesively bonded joints. One approach to improving adhesive bonding in composites is accurately measuring the thickness of adhesive bondlines in composite laminates. Precise bondline thickness control is essential for aerospace applications where adhesive layer thickness directly affects joint fracture properties and structural performance. This study focused on implementing machine learning techniques to determine the ultrasonic time of flight (directly correlated to thickness) in adhesive bondlines throughout autoclave cure cycles. A high-temperature (use up to 180°C) ultrasonic scanning system was deployed in an autoclave to provide time of flight data through composite panels. Three experiments were conducted on the curing of 305 mm × 305 mm unidirectional composite panels. In the first experiment, a piecewise function was fit for the temperature correction factor to account for changing autoclave temperatures. Due to deficiencies in the first calibration experiment, a second experiment was run, and the results were used to train a machine learning model. The revised experiment, in combination with the machine learning model, significantly increased the accuracy of the bondline time of flight predictions (~14% error reduced to <1%). Data was processed using the Regression Learner Application in MATLAB®, with a Support Vector Machine selected for the model. The result was a machine learning algorithm capable of reliably quantifying ultrasonic time of flight through adhesive bondlines. The third experiment provided independent test data for the machine learning model, demonstrating that the model produces accurate predictions from data beyond its training set.

Machine Learning↗
DOE OSTI2016

INVESTIGATION OF IN-AUTOCLAVE ADDITIVE MANUFACTURING COMPOSITE TOOLING

The autoclave is a crucial piece of equipment for fabricating Tier 1 polymer composite aerospace structural components with very low void content (i.e. < 5 %). The essential component in this composite manufacturing process is the rigid mold that defines the final shape of the fabricated composite component. The Big Area Additive Manufacturing (BAAM) system located at Oak Ridge National Laboratory s (ORNL) Manufacturing Demonstration Facility (MDF) has been used to manufacture a new generation of in-autoclave tools that can be used to fabricate various aerospace composite parts. Different tools made form Polyphenylene sulfide (PPS) with 50 % by weight carbon fiber and Polyphenylsulfone (PPSU) with 25 % carbon fiber are investigated in this study. The behavior of the printed tools under different temperature ramp rates for the autoclave cycles was observed and analyzed.

Kunc, Vlastimil↗
DOE OSTI2018

Investigating grid-to-rod fretting wear of nuclear fuel claddings using a unique autoclave fretting rig

Fuel rods in a pressurized water nuclear reactor (PWR) experience coolant flow-induced relative motion against the grid support features, a phenomenon called grid-to-rod fretting (GTRF), which may cause progressive fretting wear damage. Wear-through of the cladding on fuel rods will leak the radioactive fuel into the coolant loop to significantly increase the radiation level in PWR primary loop and often trigger expensive Post Irradiation Examination. In this work, a unique autoclave fretting test rig was designed and fabricated to allow studying GTRF using actual cladding and grid materials. Water temperature was up to 220 °C, which was designed to mimic the environment in an industry full-assembly reactor core simulator. The contact load (0.1–1 N), oscillation frequency (20–30 Hz) and stroke (50–150 µm), and work rate (1–3 mW) were defined based on simulations of GTRF in an actual reactor. Using this autoclave GTRF rig, tests were conducted to learn the effect of water temperature and to investigate the wear behavior of different cladding-grid material combinations currently used in actual PWRs, including Zr alloy claddings without and with pre-oxidation against Zr alloy and Inconel grids. Higher water temperature evidently increased the cladding wear, and pre-oxidation of the Zr alloy and/or using the Inconel grid effectively reduced the wear rate. In conclusion, results were correlated with the data of a full-size industry reactor core simulator in terms of both wear rate and wear scar morphology.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2011

In situ time-resolved X-ray diffraction of tobermorite formation in autoclaved aerated concrete: Influence of silica source reactivity and Al addition

The hydrothermal formation of tobermorite during the processing of autoclaved aerated concrete was investigated by in situ X-ray diffraction (XRD) analysis. High-energy X-rays from a synchrotron radiation source in combination with a newly developed autoclave cell and a photon-counting pixel array detector were used. To investigate the effects of the silica source, reactive quartz from chert and less-reactive quartz from quartz sand were used as starting materials. The effect of Al addition on tobermorite formation was also studied. In all cases, C-S-H, hydroxylellestadite and katoite were clearly observed as intermediates. Acceleration of tobermorite formation by Al addition was clearly observed. However, Al addition did not affect the dissolution rate of quartz. Two pathways, via C-S-H and katoite, were also observed in the Al-containing system. These results suggest that the structure of initially formed C-S-H is important for the subsequent tobermorite formation reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Well-defined crystallites autoclaved from the nitrate/NH{sub 4}OH reaction system as the precursor for (Y,Eu){sub 2}O{sub 3} red phosphor: Crystallization mechanism, phase and morphology control, and luminescent property

Autoclaving the rare-earth nitrate/NH{sub 4}OH reaction system under the mild conditions of 120-200 Degree-Sign C and pH 6-13 have yielded four types of well-crystallized compounds with their distinctive crystal shapes, including Ln{sub 2}(OH){sub 5}NO{sub 3}{center_dot}nH{sub 2}O (Ln=Y and Eu) layered rare-earth hydroxide (hexagonal platelets), Ln{sub 4}O(OH){sub 9}NO{sub 3} oxy-hydroxyl nitrate (hexagonal prisms and microwires), Ln(OH){sub 2.94}(NO{sub 3}){sub 0.06}{center_dot}nH{sub 2}O hydroxyl nitrate (square nanoplates), and Ln(OH){sub 3} hydroxide (spindle-shaped microrods). The occurrence domains of the compounds are defined. Ammonium nitrate (NH{sub 4}NO{sub 3}) as a mineralizer effectively widens the formation domains of the NO{sub 3}{sup -} containing compounds while leads to larger crystals at the same time (up to 0.3 mm). Crystallization mechanisms of the compounds and the effects of NH{sub 4}NO{sub 3} were discussed. Optical properties (PLE/PL) of the four phases were characterized in detail and were interpreted from the different site symmetries of Eu{sup 3+}. The compounds convert to cubic-structured (Y{sub 0.95}Eu{sub 0.05}){sub 2}O{sub 3} by annealing at 600 Degree-Sign C while retaining their original crystal morphologies. The resultant phosphor oxides of diverse particle shapes exhibit differing optical properties, in terms of luminescent intensity, asymmetry factor of luminescence and fluorescence lifetime, and the underlying mechanism was discussed. - Graphical abstract: Well-defined crystallites of the various phases have been autoclaved from the nitrate/NH{sub 4}OH reaction system. Crystallization mechanisms of the compounds and the effects of NH{sub 4}NO{sub 3} were discussed. Highlights: Black-Right-Pointing-Pointer Well-defined crystallites of four phases have been hydrothermally synthesized. Black-Right-Pointing-Pointer The occurrence domains of the compounds are defined. Black-Right-Pointing-Pointer Crystallization mechanisms and the effects of NH{sub 4}NO{sub 3} mineralizer are discussed. Black-Right-Pointing-Pointer PL properties of the compounds and their calcination products are studied.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Simulation Assisted Design for an Additively Manufactured Autoclave Tool Accounting for an Anisotropic Expansion

Carbon fiber reinforced polymer composites have been used in Big Area Additive Manufacturing (BAAM) to decrease the distortion during the printing process and increase functional stiffness. These materials are also important for additively manufactured autoclave tooling which expands when exposed to the high temperatures of the operational cycle, causing the dimensions of the mold to differ from the targeted design. Since the reinforcing fibers generally align during the extrusion process, the thermal expansion of the composite along the deposition direction is restrained by fibers, whereas the thermal expansion perpendicular to the bead is largely unconstrained. This leads to an anisotropic expansion of the material that is dependent upon the local deposition path, which may be tortuous and complex. To obtain an accurate final part geometry during the autoclave process, a computational prediction of the thermal expansion of a tool is required to account for the complex extrusion deposition directions. A multi-step approach is presented that accounts for (1) anisotropic thermal expansion of the extruded bead, (2) the complex deposition directions, and (3) internal geometry determined by slicing software. The thermal expansion coefficient in the deposition direction and perpendicular to the deposition direction were measured at multiple locations in the test specimen. A revised model geometry was generated to achieve the target dimensions when accounting for thermal expansion.

Hassen, Ahmed↗
NASA NTRS1971

The development of autoclave processable, thermally stable adhesives for titanium alloy and graphite composite structures

The A-type polyimide adhesive resin P11B was modified by use of mixed diamines (thio-dianiline and meta phenylene diamine) which provided the desired autoclave processability. This new resin was termed P11BA. It was shown that copolymeric blends of P11BA and Amoco AI-1137 amide-imide resin provided improved adhesive properties when autoclave processed over the properties obtained previously by press bonding with P11B based copolymeric blended adhesives. Properties of bonded assemblies are presented for long-term aging at both elevated and low temperatures, and also stress-rupture tests at elevated temperature.

Vaughan, R. W.↗