A thermoplastic resin matrix and its physical properties suitable for deformable mandrel

The mandrel is able to shape the part cavity, therefore is of great significance for composite parts in the manufacturing of carbon fiber reinforced polymer(CFRP) composite part. However, in the manufacturing of composite parts with complex cavities, traditional rigid mandrel cannot be removed out of the cavity in any direction after the outer prepreg is cured. To solve the problem of difficult demolding, a kind of deformable mandrel emerged. The deformable mandrel is rigid at room temperature to support composite part curing. While at relatively high temperatures, the mandrel is softened so that the mandrel can be easily removed from the composite part despite the complex part cavity shape, therefore resolving complications regarding the demolding process. In this paper, a thermoplastic resin material matrix suitable for the preparation of deformable mandrel is proposed. Ingredient and manufacturing flow of the thermoplastic resin matrix are introduced, and the applicability of the proposed matrix with regard to the deformable mandrel is validated through dynamic mechanical analysis.

The facultative human oral pathogen Prevotella histicola in equine cheek tooth apical/ periapical infection: a case report

Background Prevotella histicola is a facultative oral pathogen that under certain conditions causes pathologies such as caries and periodontitis in humans. Prevotella spp. also colonize the oral cavity of horses and can cause disease, but P. histicola has not yet been identified. Case presentation A 12-year-old Tinker mare was referred to the clinic for persistent, malodorous purulent nasal discharge and quidding. Conservative antibiotic (penicillin), antiphlogistic (meloxicam), and mucolytic (dembrexine-hydrochloride) treatment prior to referral was unsuccessful and symptoms worsened. Oral examination, radiography, sino-/ rhinoscopy, and standing computed tomography revealed severe apical/ periapical infection of the upper cheek tooth 209 with accompanying unilateral sinonasal inflammation and conchal necrosis. The tooth exhibited extensive subocclusal mesial infundibular cemental hypoplasia and caries, and an occlusal fissure fracture. After mechanical debridement and thermoplastic resin filling of the spacious subocclusal carious infundibular lesion, the tooth was extracted intraorally. The sinusitis and conchal necrosis were treated transendoscopically. Selective bacteriological swab cultures of affected tooth roots and subsequent matrix-assisted laser desorption ionization-time of flight mass spectrometry showed an infection with the obligate anaerobic, Gram-negative bacterium P. histicola. Surgical intervention and adapted antibiotic therapy led to normal healing without complications. Conclusions This study provides the first documented case of dental infection in a horse caused by P. histicola at once indicating necessity of more sufficient microbiological diagnostics and targeted antibiotic treatment in equine dental practice. This finding is also conducive to understand species-specific Prevotella diversity and cross-species distribution.

Optimal Design and Testing of a Thermoplastic Pressurized Passenger Door Manufactured Using Thermoforming

The present paper documents and discusses research work associated with a newly designed passenger door structure demonstrator. The composite structure was manufactured from carbon-fiber-reinforced thermoplastic resin. A composite frame with a variable cross-section was designed, optimized, and fabricated using thermoforming technology. Both numerical simulations and experiments supported structural verification according to the damage tolerance philosophy; i.e., impact damage is presented. The Tsai-Wu and maximal stress criteria were used for damage analysis of the composite parts. Topological optimization of the metal hinges from the point of view of weight reduction was used. All expected parameters and proposed requirements of the mechanical properties were proved and completed. The door panel showed an expected numerically evaluated residual strength (ultimate structure load) as well as meeting airworthiness requirements. No impact damage propagation in the composite parts was observed during mechanical tests, even though visible impact damage was introduced into the structure. No significant difference between the numerical simulations and the experimentally measured total deformation was observed. Repeated deformation measurements during fatigue showed a nonlinear structure behavior. This can be attributed to the relaxation of thermoplastics.

Investigating the adhesive properties of polymers for 3D printing

The article presents the research of adhesive properties of various polymers used in additive manufacturing by fused deposition modeling. Tensile tests of additively manufactured samples of various polymers are carried out, electro-microscopic photographs of the working area are taken before and after tests, and studies on the manufacturability of printing are performed to exclude further typical errors identified during these tests. Samples of the following polymers are studied: thermoplastic resin acrylonitrile butadiene styrene (ABS +), thermoplastic resin acrylonitrile butadiene styrene with the addition of titanium nitrite as a dye (ABS + TiN), thermoplastic resin acrylonitrile butadiene styrene with the addition of polyester inserts (ABS polylactide (PLA), polylactide based compound (PLA HP), thermoplastic polyethylene terephthalate glycol (PETG), and nylon with carbon inserts (NSC). The work reveals the advantages and disadvantages of the investigated plastics. For example, deformations occur when the part is cooled down during printing process of ABS +, and a crack could form in stress concentrators as a result of the influence of cold air flows.

Research of polymers strength properties for 3D printing under normal conditions

An article is devoted to the study of the strength properties of interlayer adhesion and determination of Young's modulus by the ball instrumental indentation method for samples, made of various plastics using additive technology under normal conditions. This production method is chosen as the most appropriate for creating lightly stressed parts of complex geometry (up to 30 MPa) in the shortest possible time. One of the possible options for such products is full-size centrifugal wheels layouts of low power gas turbine units (up to 250 kW) for testing them in model conditions. It will ensure the work of the material in the elastic zone. The samples are considered, obtained by FDM method from various polymers such as: acrylonitrile butadiene styrene thermoplastic resin (ABS+), acrylonitrile butadiene styrene thermoplastic resin with addition of carbon fibers (ABS Carbon), nylon with addition of carbon fibers (Nylon Super Carbon), polyethylene terephthalate glycol (PETG) and a compound based on polylactide (PLA HP). Plastics, made by this method, have anisotropic properties. Therefore, in this work, the strength characteristics of the test samples interlayer adhesion under tension are determined.

Effect of Interpenetrating Polymer Network (IPN) Thermoplastic Resin on Flexural Strength of Fibre-Reinforced Composite and the Penetration of Bonding Resin into Semi-IPN FRC Post

The purpose of this study was to evaluate the effects of interpenetrating polymer network (IPN) thermoplastic resin on the flexural strength of fibre-reinforced composite (FRC) with different IPN polymer compositions. The penetration of bonding resin into semi-IPN FRC posts was also evaluated. The IPN thermoplastic resin used was UDMA-MMA monomer with either PMMA (0.5%, 2%, 5%) or PMMA-copolymer (0.5%, 2%). A no added IPN polymer resin was also made. Mixed resin was impregnated to S- and E-glass fibre rovings. These resins and resin impregnated fibres were used for flexural strength (FS) test. To evaluate the penetration of bonding resin into semi-IPN post, SEM observation was done with various impregnation time and polymerization mehods (hand-light- and oven-cure). The result of FS was recorded from 111.7 MPa (no-IPN polymer/no-fibre-reinforcement) to 543.0 MPa (5% PMMA/S-glass FRC). ANOVA showed that there were significant differences between fibre-reinforcement and no-fibre-reinforcement (p < 0.01) both in S- and E-glass fibre groups, and between 0.5% PMMA and 5% PMMA in the S-glass FRC group. SEM micrographs showed that the penetration layers of bonding resin into hand-light cured semi-IPN posts were different according to impregnation time. Fibre reinforcement is effective to improve flexural strength. The depth of penetration layer of bonding resin into semi-IPN matrix resin was improved when a hand-light cure was used.