Development of Laser Processing Carbon-Fiber-Reinforced Plastic.

Due to its exceptional advantages, such as high specific strength, high specific modulus, and good fatigue resistance, carbon-fiber-reinforced plastic (CFRP) is frequently utilized in aerospace, aviation, automotive, rail transportation, and other areas. Composite components typically need to be joined and integrated. In the equipment manufacturing industry, the most used methods for processing composite components are cutting, drilling, and surface treatment. The quality of CFRP is significantly impacted by traditional mechanical processing, causing flaws like delamination, burrs, and tears. Laser processing technology has emerged as a crucial method for processing CFRP for its high quality, non-contact, simple control, and automation features. The most recent research on the laser processing of CFRP is presented in this paper, supporting scientists and engineers who work in the field in using this unconventional manufacturing technique. This paper gives a general overview of the key features of laser processing technology and the numerous machining techniques available. The concepts and benefits of laser processing technology are discussed in terms of the material properties, mode of operation, and laser characteristics, as well as the methods to achieve high efficiency, low damage, and high precision. This paper reviews the research development of laser processing of carbon-fiber-reinforced plastics, and a summary of the factors affecting the quality of CFRP laser processing. Therefore, the research content of this article can be used as a theoretical basis for reducing thermal damage and improving the processing quality of laser-processed composite materials, while, on this basis, we analyze the development trend of CFRP laser processing technology.

Experimental study of different pulse delays on the phenomenon of double shock waves induced by a millisecond-nanosecond combined-pulse laser.

We study the motion morphology, distance, and velocity of plasma and laser-induced shock waves induced by a millisecond-nanosecond (ms-ns) combined-pulse laser with different pulse delays on silicon. The laser shadowgraph method is used, and the phenomenon of double laser-induced shock waves has been found while the pulse delay is 1.2-1.8 ms. The controlling variable method is used to study this phenomenon, and it is found that it is mainly related to the ignition of the laser-supported absorption wave induced by the ms laser. Moreover, the plasma expansion velocity increases with the increase of pulse delay, the axial propagation distance of laser-induced shock waves increases monotonically with pulse delay, and the velocity of laser-induced shock waves decreases with the increase of pulse delay.

Experimental study of the morphological evolution of the millisecond-nanosecond combined-pulse laser ablation of aluminum alloy.

A comparative study of the interactions of the millisecond-nanosecond combined-pulse laser and millisecond pulse laser with aluminum alloy is presented. During the interaction between the laser and aluminum alloy, the coupling effect of the nanosecond pulse laser on the molten pool formed by the millisecond laser is analyzed. During the nanosecond laser irradiation in the combined approach, the expansion velocity of the plasma plume reaches 600 m/s, while the laser ablation depth increased by approximately 9 times. Based on experiments, the high-speed shadow imaging method, correlation of the temperature evolution characteristics, and ablation morphology are considered for a comprehensive analysis. The coupling effect between the millisecond-nanosecond combined-pulse laser and aluminum-alloy molten pool phase is explained.

The Effect of Spot Size Combination Mode on Ablation Morphology of Aluminum Alloy by Millisecond-Nanosecond Combined-Pulse Laser.

Ablation morphology affects the quality of laser processing. Therefore, the control of ablation morphology is very important. The influence of spot size combination mode on the ablation morphology of aluminum alloy is studied for the first time. Experimental results show that when the nanosecond laser spot is larger, the ablation morphology looks like a bowl-shape, and there is little solidification near the edge. When the nanosecond laser spot is smaller, the shape of the ablation morphology is similar to a hole, and the protuberance is formed near the edge of the cavity. Through the analysis and simulation of the physical model, the physical mechanism, which describes the influence of the spot size combination mode on the molten pool, is discussed. The research results of this paper have important guiding significance for the control of laser processing effect.

Long-term outcomes of endoscopic multiband mucosectomy for early esophageal squamous cell neoplasia: a retrospective, single-center study.

BACKGROUND AND AIMS: Endoscopic multiband mucosectomy (EMBM) has been used to treat early Barrett's esophagus and esophagogastric junction neoplasia, yet it is seldom reported for the treatment of early esophageal squamous cell neoplasia. Here we retrospectively evaluated the feasibility, safety, and efficacy of EMBM for early esophageal squamous cell neoplasia. METHODS: A total of 125 patients were included in the study. Lesions were delineated using electrocoagulation and resected using the EMBM technique. The primary outcomes were local recurrence and adverse events. Secondary outcomes were histology of the endoscopic resection specimens, specimen area, and speed of resection. All patients were followed up endoscopically. RESULTS: There were 135 esophageal lesions, of which 40 were pathologically diagnosed as low-grade intraepithelial neoplasia, 57 as high-grade intraepithelial neoplasia, 34 as early esophageal cancer, and 4 as squamous epithelium without neoplasia. No severe adverse events were observed, except for 1 perforation, which was treated by application of clips. The median follow-up was 27.75 months. Three patients had local recurrence and were endoscopically treated again. Local recurrence rate was 2.4% (3/125). No deaths occurred during the follow-up. All specimens were visible with a dividing rule, and the mean specimen area was 4.63 cm2. Mean operation time was 31.2 ± 17.4 minutes. Mean speed of resection was 6.74 min/cm2. CONCLUSIONS: EMBM seems to be effective and safe for patients with early esophageal squamous cell neoplasia. The long-term recurrence rate is low.

Faecal calprotectin concentrations in gastrointestinal diseases.

OBJECTIVE: To quantify faecal calprotectin concentrations in a variety of gastrointestinal disorders in order to determine its diagnostic value. METHODS: Patients with gastrointestinal symptoms undergoing upper or lower endoscopy and healthy control subjects provided stool samples. Calprotectin was quantified by enzyme-linked immunosorbent assay. RESULTS: The study recruited 210 patients with definitively diagnosed gastrointestinal diseases and 50 control subjects. Calprotectin concentrations were significantly higher in patients with ulcerative colitis or Crohn's disease compared with controls, or patients with colorectal polyps or irritable bowel syndrome. The faecal calprotectin concentration significantly differentiated between inflammatory bowel diseases (IBD) and non-IBD (area under ROC curve 0.949). Calprotectin concentrations were significantly higher in patients with oesophageal polyps or gastric neoplasms than in those with chronic gastritis, stomach ulcers, duodenal ulcers or acute pancreatitis. CONCLUSION: Calprotectin may be a useful noninvasive marker for the diagnosis of IBD.