Gaetano Restivo

CA 19-9 to Rule Out Pancreatic or Biliary Cancer Among Patients with Cholestasis: An Unsuitable Test?

Carbohydrate antigen CA 19-9 was initially proposed as a serologic marker for colorectal cancer [1]. Nowadays its use is not recommended for this purpose [1] and CA 19-9 serum concentration is mostly evaluated in patients with suspected pancreatic or biliary cancer, because of its presumed higher specificity in this setting [2–5]. Unfortunately, CA 19-9 levels have also been reported in other malignancies such as gastric and ovarian cancer and in different benign conditions like cystic fibrosis, hydronephrosis, and Hashimoto thyroiditis [5–7]. Furthermore, elevated CA 19-9 serum concentration can be associated with several conditions producing reduced biliary drainage [8–10], especially in the presence of cholangitis [11]. It is generally be-

Effects of Clearance on Thick, Single-Lap Bolted Joints Using Through-the-Thickness Measuring Techniques

Composite materials have increasingly become more common in ground transportation. As this occured thicker panels, as compared to composite panels used in aviation, become necessary in order to withstand high impact loads and day to day degradation. The effectiveness of these panels was often limited by the strength of the joint in which the panel was attached to the frame of the vehicle. Investigating methods of reducing strain concentrations within these joints would increase the effectiveness in using composite materials in ground transportation applications by increasing the load necessary for joint failure to occur. In this study, fiber optic strain gages were embedded in a composite panel along the bearing plane of a thick, single-lap, bolted joint. The gages allow for the strain profile above the hole to be determined experimentally. Several clearance values were then implemented in the bolt to determine their effect on the strain concentrations. Strain increased at every gage, by nearly the same proportion, when clearance was increased from zero to three percent. When clearance was further increased to five percent strain only continued to increase at gages three and four, with one and two remaining similar in value to what was seen at three percent clearance. Ultimately, like in thin composite panels, the zero percent clearance condition was the stiffest.

Novel Insert Design for Thick Single Lap Bolted Composite Joints

Mechanical fastening is popular choice in joining composites because of the ability to transfer high loads and the ease of assembly and disassembly. However, drilling operations expose the fibers to environmental factors, and the high contact stresses between the bolt and the hole lead to localized delaminations, decreasing the joint strength. A new insert design, proposed here, seals the joint and increases the contact area between the bolt and the hole. This design is also low-cost and compatible with current machining techniques. With the novel design, a phase changing liquid is injected into the empty region between the bolt and the hole. The liquid is then allowed to cure. The tests the performed are on non-reinforced joints and joints reinforced with both machined isotropic inserts and the novel design. Initial tests in the elastic range are analyzed by using Digital Image Correlation. The joints are also tested to Ultimate failure to determine any trends. Form these tests and other preliminary considerations, it can be concluded that the novel design has tremendous potential for applications involving thick composite joints.