RESUMO
Fiber-reinforced polymer (FRP) composites play a vital role in the production of structural and semi-structural components for engineering applications. The drilling process is a commonly employed machining process for FRP composites to join the FRP structural elements. Usually, the FRP composites possess a heterogeneous nature because of their multi-layered structure, hybridization, and the presence of multi-phase materials. Hence, common problems like delaminations, fuzzing, buckling, cracking, matrix and fiber burning occur during the drilling operations. These problems cause dimensional inaccuracy, poor surface finish, and tool wear and reduce the mechanical strength of the composites. The optimum drilling parameters (drill geometry, speed, feed, and depth of cut) selection for the specific materials is good to achieve effective drilling performance and better surface quality of the holes. Yet, little study has been done on how all of these factors affect the size of the drilled hole. The majority of drilling studies on FRPCs in the past have focused on how to improve the hole quality by maximizing processing conditions, and there has been little discussion on the correlation between drilling conditions, physical properties, and production techniques. This is what motivated to review the characteristics and properties analysis of FRP composites. As a consequence of this research, it is anticipated that scientists and researchers would place a greater emphasis on the drilling characteristic of the workpieces made from FRPCs than on other attributes. This review clearly presents an overview of FRP composites drilling that had progressed from 2000 to 2021. The analysis of different drilling conditions and parameters like thrust force, drill geometry, temperature, speed, and feed also includes the post-drilling analysis through delaminations, thermal damage, and surface roughness. Furthermore, the recent developments in carbon, glass, and natural fiber reinforced polymer composites are studied with both conventional and nonconventional drilling techniques. Based on the above studies, some future challenges and conclusions are drawn from this review.
RESUMO
Oxyntic gastric heterotopia (GH) in the colon is not common. Its presence in a colon tubular adenoma is even rare. A 73-year-old woman with a history of resected colon carcinoma underwent periodical colonoscopies for the removal of tubular adenomas for 12 years. In the last colonoscopy, a sessile, non-ulcerated polyp, centrally depressed, with a smooth surface, measuring 20 mm, located at 50 cm from the anal verge was excised. A histological study identified a tubular adenoma with focal low-grade dysplasia and ectopic gastric oxyntic epithelium. The GH, composed of parietal and chief cells, and was found incidentally. Oxyntic GH in a tubular adenoma is extraordinarily rare. To the best of our knowledge, there is only one previously published case. The main possible difficulties and∕or errors in the diagnosis include a tissue floater or a cross-contaminant. Precise diagnosis of oxyntic GH is basic for appropriate management. Diagnosis relies on histopathological examination. The immunohistochemical study for mucin 6 (MUC6) can confirm the nature of the epithelium. Oxyntic GH has the potential to produce serious complications including tumor development. However, GH is considered a benign disease and adenocarcinoma rarely occurs in the heterotopic mucosa. The optimal treatment of oxyntic GH associated with a tubular adenoma is endoscopic complete polypectomy.
