High-performance molded composites using additively manufactured preforms with controlled fiber and pore morphology

Kumar, Vipin; Alwekar, Shailesh; Kunc, Vlastimil; Cakmak, Ercan; Kishore, Vidya; Smith, Tyler; Lindahl, John; Vaidya, Uday; Blue, Craig A.; Theodore, Merlin; Kim, Seokpum; Hassen, Ahmed Arabi

doi:10.1016/j.addma.2020.101733

Cited by 18 publications

(14 citation statements)

References 19 publications

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“…The most common feedstock for LFAM printers is acrylonitrile butadiene styrene (ABS), often blended with chopped fibers to improve mechanical properties and reduce warp [99][100][101]. Depending on processing, the reported flexural modulus for neat ABS used in the BAAM printer ranges from 1.87 GPa-2.45 GPa, while flexural strength varies from 58.6 MPa-68.3 MPa [4]. All tested photopolymer formulations in the present study exceeded the flexural strength of ABS by an average of 46-71% and the flexural modulus of ABS by an average of 25-44%.…”

Section: Flexural Testingmentioning

confidence: 99%

“…Large-format additive manufacturing (LFAM) is a nascent technology, emerging as an efficient method for producing structural components and tooling for low-volumecomposites manufacturing [1][2][3][4][5][6]. LFAM refers to polymer-extrusion-deposition methods that achieve both large-scale and high-material throughput during printing.…”

Section: Introductionmentioning

confidence: 99%

“…However, such systems use rare-earth metals and are not currently in widespread use [28]. 4 Various photopolymer chemistries have been developed with the ability to cure regions that are not directly exposed to the irradiated light [34,42,59,60], a phenomenon also known as "shadow cure" or "dark cure". The most common of these are cationiccuring systems, in which UV energy generates a protonic acid to initiate a ring opening of epoxy resins [27].…”

Section: Introductionmentioning

confidence: 99%

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Photoinitiator Selection and Concentration in Photopolymer Formulations towards Large-Format Additive Manufacturing

et al. 2022

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Photopolymers are an attractive option for large-format additive manufacturing (LFAM), because they can be formulated from structural thermosets and cure rapidly in ambient conditions under low-energy ultraviolet light-emitting diode (UV LED) lamps. Photopolymer cure is strongly influenced by the depth penetration of UV light, which can be limited in the 2–4 mm layer thicknesses typical of LFAM. Photoinitiator (PI) systems that exhibit photobleaching have proven useful in thick-section cure applications, because they generate a photoinitiation wavefront, but this effect is time-dependent. This study investigates the light transmission and through-thickness cure behavior in (meth)acrylate photopolymer formulations with the photobleaching initiator bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (BAPO). Utilizing an optical model developed by Kenning et al., lower concentrations (0.1 wt% to 0.5 wt%) of BAPO were predicted to yield rapid onset of photoinitiation. In situ cure measurements under continuous UV LED irradiation of 380 mW/cm2 showed that a 0.1 wt% concentration of BAPO achieved peak polymerization rate within 2.5 s at a 3-mm depth. With only 1 s of irradiation at 1.7 W/cm2 intensity, the 0.1 wt% BAPO formulation also achieved the highest level of cure of the formulas tested. For an irradiation dose of 5.5 J/cm2 at a duration of 3.7 s, cured polymer specimens achieved a flexural strength of 108 MPa and a flexural modulus of 3.1 GPa. This study demonstrates the utility of optical modeling as a potential screening tool for new photopolymer formulations, primarily in identifying an upper limit to PI concentration for the desired cure depth. The results also show that photobleaching provides only a limited benefit for LFAM applications with short (1.0 s to 3.7 s) UV irradiation times and indicate that excess PI concentration can inhibit light transmission even under extended irradiation times up to 60 s.

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Section: Flexural Testingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Photoinitiator Selection and Concentration in Photopolymer Formulations towards Large-Format Additive Manufacturing

et al. 2022

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“…Qinghao He [ 27 ] quantified the adverse effects of voids on 3D-printed continuous fiber-reinforced polymer composites. Vipin Kumar [ 28 ] produced a large-scale multimaterial by additive manufacturing (AM) undergoing compression molding (CM) to produce high-performance thermoplastic composites reinforced with short carbon fibers. Zhu Liu [ 29 ] established a microscale unit cell with a random distribution of fibers, interfaces, and voids based on the random sequential adsorption algorithm to investigate the quantitative effects of void content on the strength and modulus under the loading of transverse tension.…”

Section: Introductionmentioning

confidence: 99%

Research on Void Dynamics during In Situ Consolidation of CF/High-Performance Thermoplastic Composite

et al. 2022

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Automated fiber placement (AFP) in situ consolidation of continuous CF/high-performance thermoplastic composite is the key technology for efficient and low-cost manufacturing of large thermoplastic composites. However, the void in the in situ composite is difficult to eliminate because of the high pressure and the short consolidation time; the void content percentage consequently is the important defect that determines the performance of the thermoplastic composite parts. In this paper, based on the two-dimensional Newtonian fluid extrusion flow model, the void dynamics model and boundary conditions were established. The changes of the void content percentage were predicted by the cyclic iteration method. It was found that the void content percentage increased gradually along the direction of the layers’ thickness. With the increasing of the laying speed, the void content percentage increased gradually. With the increasing of the pressure of the roller, the void content percentage gradually decreased. When the AFP speed was 11 m/min and the pressure of the compaction roller reached 2000 N, the void content percentage of the layers fell below 2%. It was verified by the AFP test that the measured results of the layers’ thickness were in good agreement with the predicted results of the model, and the test results of the void content percentage were basically equivalent to the predicted results at different AFP speeds, which indicates that the kinetic model established in this paper is representative to predict the void content percentage. According to the metallographic observation, it was also found that the repeated pressure of the roller was helpful to reduce the void content percentage.

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“…[1][2][3][4] The conventional methods of scaffolds fabrication, for instance, gas foaming, solvent casting, and freeze-drying, could not precisely control the pore size, porosity, and geometrical morphology, which are very essential to regulate tissue regeneration process. Therefore, in the past decade, 3D printing technology has been extensively developed and become a popular way to prepare porous scaffolds for tissue engineering, which can not only fabricate on-demand micro-structure, morphology, and porosity, [5][6][7] but also combine materials with cells and growth factors to promote tissue regeneration. 8,9 Numerous 3D printed scaffolds have been fabricated and used for bone tissue engineering applications and many of them showed interesting performances in bone repair and regeneration.…”

Section: Introductionmentioning

confidence: 99%

A facile way to construct Sr-doped apatite coating on the surface of 3D printed scaffolds to improve osteogenic effect

Chen

Wang

2022

J Biomater Appl

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Bone-like apatite coating fabricated by biomineralization process is a facile way for surface modification of porous scaffolds to improve interfacial behaviors and thus facilitate cell attachment, proliferation, and differentiation for bone tissue engineering. In this study, a Sr-containing calcium phosphate solution was made and used to construct a thick layer of Sr-doped bone-like apatite on the surface of 3D printed scaffolds via biomineralization process. Importantly, Sr-doped bone-like apatite could form and fully cover the 3D printed scaffolds surface in hours. The characterization results indicated that Sr2+ ions successfully replaced Ca2+ ions in bone-like apatite and the molar ratio of Sr/(Ca+Sr) was up to 8.2%. Furthermore, the Sr-doped apatite coating increased the compressive strength and Young’s modulus of composite scaffolds. The compatibility and bioactivity of mineralized scaffolds were evaluated by cell attachment, proliferation, and differentiation of MC3T3-E1 cells. It was found that Sr-doped apatite coating could gradually release Sr2+ ions and further promote cell attachment, proliferation rate, and the expression of alkaline phosphatase activity and osteogenic related genes, such as collagen type I (Col I), Runt-related transcription factor 2 (Runx-2), osteopontin, and osterix. Therefore, the Sr-doped apatite coating fabricated by this facile and rapid biomineralization process offers a new strategy to modify 3D printed porous scaffolds with significantly improved mechanical and biological properties for bone tissue engineering applications.

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High-performance molded composites using additively manufactured preforms with controlled fiber and pore morphology

Cited by 18 publications

References 19 publications

Photoinitiator Selection and Concentration in Photopolymer Formulations towards Large-Format Additive Manufacturing

Photoinitiator Selection and Concentration in Photopolymer Formulations towards Large-Format Additive Manufacturing

Research on Void Dynamics during In Situ Consolidation of CF/High-Performance Thermoplastic Composite

A facile way to construct Sr-doped apatite coating on the surface of 3D printed scaffolds to improve osteogenic effect

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