Holes in composites are a necessity for joining and fastening parts together; however, they also create large stress concentrations that often initiate failure. The cause of these stress concentrations originate at the broken fiber ends around the hole perimeter that are produced by the hole forming process (drilling or punching). This arti cle presents an innovative hole design that was inspired by biomimetics research for reduc ing stress concentrations.
This study was initiated to investigate the structural response of the bessbeetle to determine potential advantageous ramifications and effects on the optimization of synthetic composite materials. The result of the micromechanics sensitivity study of various parameters are presented. Variables such as fiber size and shape, fiber volume fraction, ratio of modulus of elasticity of fiber over matrix, are changed one variable at a time, and the response quantities such as stress and tranverse modulus are presented.
The failure processes of the bessbeetle cuticle were studied through the use of scanning electron microscopy, light microscopy, and image analysis techniques. Specimens of elytra and pronotum were failed in tension under the light microscope. The failure process was documented in real time through the use of image analysis equipment and a video camera. Failure occurs primarily in a mixed-mode fashion due to the inherent curvature of the cuticle specimens and their complex hierarchical microstructure. A variety of energy-absorbing mechanisms were observed including remote microcracking, fiber pullout, and crack bridging. Damage accumulation around the failed region is extensive consisting of a significant amount of delamination, fiber-matrix disbonds, microcracking, and intra-fiber failure. The experimental methods and results will be discussed.
The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information , 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YY)2. REPORT TYPE 3. DATES COVERED (From -To) SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORING AGENCY ACRONYM(S)AFRL AFRL-ML-WP-TP-2007-421 DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution unlimited. SUPPLEMENTARY NOTESThe U.S. Government is joint author of this work and has the right to use, modify, reproduce, release, perform, display, or disclose the work. PAO Case Number: AFRL/WS 06-2822, 07 Dec 2006. Paper contains color content. ABSTRACTThe amount of hydraulic fluid used by all branches of the military is significant both in terms of volume and cost. The disposal of used hydraulic fluid is a cost, time, and logistical component that can be greatly reduced by the purification and reuse of used hydraulic fluid. This report describes a project that evaluated the effectiveness of various hydraulic fluid purification process configurations on the removal of water and particulate contaminants from MIL-PRF-83282 hydraulic fluid in 55-gallon drums. SUBJECT TERMS IntroductionThe amount of hydraulic fluid used by all branches of the military is significant both in terms of volume and cost. The disposal of used hydraulic fluid is a cost, time, and logistical component that can be greatly reduced by the purification and reuse of used hydraulic fluid. This report describes a project that evaluated the effectiveness of various hydraulic fluid purification process configurations on the removal of water and particulate contaminants from MIL-PRF-83282 hydraulic fluid in 55-gallon drums. Materials and MethodsThe fluid used in this evaluation was fresh MIL-PRF-83282 hydraulic fluid that was contained in a 55-gallon drum. The actual fluid amount contained in the drum and subjected to the purification process was approximately 53 gallons. The purifier used in the tests was a Pall portable purification unit model #PE-00440-1Z ( Figure 1) and all testing was carried out under ambient conditions (above 60°F/15°C). A slurry of natural Arizona road dust containing particles of various sizes was introduced into clean MIL-PRF-83282 and used to simulate pa...
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