The easiest and most reliable joining method is the mechanical joint with a bolt and nut or rivet. However, in the case of composite laminates, mechanical joint properties decrease because of lower interlaminar proper...The easiest and most reliable joining method is the mechanical joint with a bolt and nut or rivet. However, in the case of composite laminates, mechanical joint properties decrease because of lower interlaminar properties compared to in-plane properties around hole.?This study investigated needle punching process with the aim of improving the mechanical properties in the thickness direction of fiber-reinforced plastic composite laminates with an open hole. Needle punching process was applied to glass fiber chopped strand matused as the reinforcement for the composite laminates. Open-hole tensile tests and observations of end cross-sections after the tests were performed. The tensile properties and fracture mechanism of the specimens subjected to needle punching process were investigated. In addition, characteristic distance (a parameter for evaluating resistance to fracture in open-hole tensile test specimens) was also calculated to examine the effects of needle punching process conditions on fracture toughness. Tensile strength was improved by more than 15% by needle punching process. However, when a certain needle punching density was exceeded, the mechanical properties worsened. In addition, characteristic distance increased with increasing needle punching density. Thus, these results suggest that there is an optimal needle punching density with respect to strength and characteristic distance.展开更多
To reveal the potential relationship between microbial community and flavor compounds during the fermentation of chopped red chili,microbial diversity and volatile metabolites at different stages were analyzed by high...To reveal the potential relationship between microbial community and flavor compounds during the fermentation of chopped red chili,microbial diversity and volatile metabolites at different stages were analyzed by high-throughput sequencing and gas chromatography-mass spectrometry.The results showed that Pseudomonas was the most dominant bacterial genus in fermented chopped red chili(FCRC),while unclassified_f__Nectriaceae and Colletotrichum were the most abundant fungal genus initially but were quickly replaced by Wickerhamomyces and Hyphopichia.Besides,citric acid and acetic acid were the most abundant organic acids,and esters were the dominant volatile flavor compounds in FCRC.Notably,the formation of flavor compounds in FCRC can be divided into three stages:the first stage is day 0,the second stage is day 3–10,and the third stage is day 15–20.Based on the O2PLS model,13 bacterial genera highly correlated(|ρ|>0.7)with flavor compounds and Exiguobacterium was correlated with 26 flavor components,having the largest numbers of correlated flavor compounds,while only four fungal genera correlated with flavor compounds(|ρ|>0.7)and unclassified_f__Nectriaceae was correlated with 11 flavor components.Moreover,the correlation analysis suggested that Exiguobacterium and Aureimonas were the core bacteria to produce the key flavors of FCRC,while unclassified_f__Nectriaceae,Wickerhamomyces and Hyphopichia were the core fungus.These findings provide novel insights into the variation of bacterial and fungal communities and increase our understanding of the core aroma-related microbiota involved in manufacturing FCRC with distinctive flavor properties.展开更多
文摘The easiest and most reliable joining method is the mechanical joint with a bolt and nut or rivet. However, in the case of composite laminates, mechanical joint properties decrease because of lower interlaminar properties compared to in-plane properties around hole.?This study investigated needle punching process with the aim of improving the mechanical properties in the thickness direction of fiber-reinforced plastic composite laminates with an open hole. Needle punching process was applied to glass fiber chopped strand matused as the reinforcement for the composite laminates. Open-hole tensile tests and observations of end cross-sections after the tests were performed. The tensile properties and fracture mechanism of the specimens subjected to needle punching process were investigated. In addition, characteristic distance (a parameter for evaluating resistance to fracture in open-hole tensile test specimens) was also calculated to examine the effects of needle punching process conditions on fracture toughness. Tensile strength was improved by more than 15% by needle punching process. However, when a certain needle punching density was exceeded, the mechanical properties worsened. In addition, characteristic distance increased with increasing needle punching density. Thus, these results suggest that there is an optimal needle punching density with respect to strength and characteristic distance.
基金funded by the Science and Technology Support Program of Guizhou Province,No.[2020]1Y156Science and Technology Talents and Platform Program of Yunnan Province,No.202105AF150049Key Laboratory of Food Microbial Resources and Utilization in Universities in Yunnan Province(Yunjiaofa[2018]No.135).
文摘To reveal the potential relationship between microbial community and flavor compounds during the fermentation of chopped red chili,microbial diversity and volatile metabolites at different stages were analyzed by high-throughput sequencing and gas chromatography-mass spectrometry.The results showed that Pseudomonas was the most dominant bacterial genus in fermented chopped red chili(FCRC),while unclassified_f__Nectriaceae and Colletotrichum were the most abundant fungal genus initially but were quickly replaced by Wickerhamomyces and Hyphopichia.Besides,citric acid and acetic acid were the most abundant organic acids,and esters were the dominant volatile flavor compounds in FCRC.Notably,the formation of flavor compounds in FCRC can be divided into three stages:the first stage is day 0,the second stage is day 3–10,and the third stage is day 15–20.Based on the O2PLS model,13 bacterial genera highly correlated(|ρ|>0.7)with flavor compounds and Exiguobacterium was correlated with 26 flavor components,having the largest numbers of correlated flavor compounds,while only four fungal genera correlated with flavor compounds(|ρ|>0.7)and unclassified_f__Nectriaceae was correlated with 11 flavor components.Moreover,the correlation analysis suggested that Exiguobacterium and Aureimonas were the core bacteria to produce the key flavors of FCRC,while unclassified_f__Nectriaceae,Wickerhamomyces and Hyphopichia were the core fungus.These findings provide novel insights into the variation of bacterial and fungal communities and increase our understanding of the core aroma-related microbiota involved in manufacturing FCRC with distinctive flavor properties.
