Investigation of the Interlaminar Shear Performance of Tufted Preforms and Composites under Mode II Loading Condition.

The influences of reinforcement by tufting on the interlaminar shear performance of laminated preforms and composites are studied in the present paper. A modified T steel shearing test was established and used to achieve a pure Mode II loading (sliding). Dry tufted preform (DTP) and cured tufted composites (CTC) with varied tufting spacing are considered for the understanding of the role of infused resin and the tufting density on the mechanical properties. Meanwhile, knowledge about the role of infused resins is gained. Additionally, cured tufted composites without threads (CT'C) were prepared under the identical tufting density to evaluate the effect of tufting threads. The results show that the denser the tufting density, the stronger the interlaminar shear strength of CTC, its improvement reaches 12% compared to the non tufted composites. However, the decreased effect also exists for the tufting spacing of 9 mm. Therefore, the tufting density needs to be optimized during the tufting process to improve the interlaminar shear properties of tufted reinforcement and composites. On the contrary, tufting without thread does not affect its mechanical properties compared to the non tufted composites.

Influence of the Unit Cell Parameters on the Thermomechanical Non-Symmetric In-Plane Shear Behavior of 2D Biaxial Braided Preform for Thermoplastic Biocomposites.

The identification of thermomechanical in-plane shear behavior of preform is one of the most important factors to ensure the quality of the thermoplastic composites during the thermoforming process. In this present work, the non-symmetric in-plane shear behavior of flax/polypropylene 2D biaxial braided preform for thermoplastic biocomposites was characterized at elevated temperature chamber by using bias-extension test. Analytical models of a bias-extension test based on non-symmetric unit cell geometry for 2D biaxial braids were defined and applied; the thermo-condition-dependent experiments were conducted to study the temperature and displacement rate dependences. The influence of unit cell geometry parameters including braiding angle, tow waviness, and cover factor on the thermal in-plane shear behavior was deeply invested, experiments in both axial and transversal directions were performed for a complete study, and asymmetric scissor mechanisms for in-plane shear behavior were introduced and studied. Finally, a simulation of thermal impregnation distribution based on unit cell geometry was made to clarify the importance of the overall fiber volume fraction.

Effect of Core Architecture on Charpy Impact and Compression Properties of Tufted Sandwich Structural Composites.

This study presents a novel sandwich structure that replaces the polypropylene (PP) foam core with a carbon fiber non-woven material in the tufting process and the liquid resin infusion (LRI) process. An experimental investigation was conducted into the flatwise compression properties and Charpy impact resistance of sandwich composites. The obtained results validate an enhancement to the mechanical properties due to the non-woven core and tufting yarns. Compared to samples with a pure foam core and samples without tufting threads, the compressive strength increased by 45% and 86%, respectively. The sample with a non-woven layer and tufting yarns had the highest Charpy absorbed energy (23.85 Kj/m2), which is approximately 66% higher than the samples without a non-woven layer and 90% higher than the samples without tufting yarns. Due to the buckling of the resin cylinders in the Z-direction that occurred in all of the different sandwich samples during the compression test, the classical buckling theory was adopted to analyze the differences between the results. The specific properties of the weight gains are discussed in this paper. The results show that the core layers have a negative effect on impact resistance. Nevertheless, the addition of tufting yarns presents an obvious benefit to all of the specific properties.

Effects of Micro-Braiding and Co-Wrapping Techniques on Characteristics of Flax/Polypropylene-Based Hybrid Yarn: A Comparative Study.

Micro-braiding and co-wrapping techniques have been developed over a few decades and have made important contributions to biocomposites development. In this present study, a set of flax/polypropylene (PP) micro-braided and co-wrapped yarns was developed by varying different PP parameters (PP braiding angles and PP wrapping turns, respectively) to get different flax/PP mass ratios. The effects on textile and mechanical characteristics were studied thoroughly at the yarn scale, both dry- and thermo-state tensile tests were carried out, and tensile properties were compared before and after the braiding process to study the braidabilities. It was observed that PP braiding angles of micro-braided yarn influenced the frictional damage on surface treatment agent of flax roving, the cohesive effect between PP filaments/flax roving, and the PP cover factor; PP wrapping turns of co-wrapped yarn had a strong impact on the flax roving damage and the PP coverage, which further influenced the characteristics. Micro-braided yarn and co-wrapped yarn with the same flax/PP mass ratio were compared to evaluate the two different hybrid yarn production techniques; it was proven that micro-braided yarn presented better performance.

Unusual acute neonatal mortality and sow agalactia linked with ergot alkaloid contamination of feed.

BACKGROUND: An increase in the occurrence of ergot alkaloid contamination has been observed in Europe in recent years. The typical clinical signs of pig ergot poisoning are impaired growth, agalactia and, sometimes, gangrene. Opportunities for reporting exposure doses associated with clinical signs in animals under field conditions are rare. CASE PRESENTATION: In a farrow-to-finish pig farm with 160 sows, excessive acute neonatal mortality was reported in association with a loss of appetite and agalactia in sows. A herd examination was conducted and a high rate of piglet loss and agalactia in 13 sows out of the most affected batch of 20 were confirmed. Necropsy showed piglets with empty stomachs and intestines, with apparently normal mucosa. Gestating and lactating sow diet samples, as well as a wheat sample, were sent for analysis following feed mill inspection and a hypothesis of mycotoxin contamination of self-prepared feed. Liquid chromatography with mass spectrometry in tandem revealed an amount of total ergot alkaloids in all of the samples ranging from 3.49 mg/kg (gestating diet) to 8.06 mg/kg (lactating diet). The contaminated feed was removed and the situation returned to normal 3 weeks later (following batch of sows). CONCLUSION: In the present case, the exposure of sows to 3.49 mg/kg ergot alkaloid for 10 to 15 days before the end of gestation and to 8.06 mg/kg ergot alkaloid over 3 to 4 days at the beginning of lactation - corresponding to a content of 10,146 mg of sclerotia/kg in the wheat of the diets- led to agalactia in 13 of 20 sows in a batch and to a high neonatal mortality rates for all litters. No clinical signs associated with vasoconstrictive effects were observed.