BS in Aerospace Engineering
Aerospace Engineering Department
The purpose of this report is to outline the path and methods used to design a specimen fixture for the testing and analysis of fiber reinforced composites subjected to impact loading. This design is done in support of the California Polytechnic State University in San Luis Obispo Structures and Composites Laboratory. The design request was made at the request of Dr. Eltahry Elghandour to support the graduate students Kodi A. Rider and Y. Vanessa Wood in their master’s degree thesis projects.
The design request involved the design of a specimen fixture compatible with the existing impact apparatus located in the laboratory. The apparatus is an Instron Dynatup 8250 HV Drop Weight Impact Testor. The design must adhere to the requirements of the testing standard ASTM D 7136 except as noted by Dr. Elghandour where the testing fixture was to be operated by a pneumatic clamping system.
The specimen fixture was designed to be made of 6061-T6 aluminum alloy. Finite element analysis was used to determine the maximum impact load that the specimen fixture could safely withstand. According to the operator’s manual of the impact tester, the maximum impact load that the specimen fixture would need to withstand was 100 lb at a velocity of 6 m/s, which translates to a force of about 31000 lbf. After structural analysis using SolidWorks Simulation FEA, the highest impact load the specimen fixture design could withstand was 45000 lbf, at which point plastic deformation would begin to occur at the welds of the central core tubular support assembly. This load far exceeds the load as specified in the operator’s manual.
The specimen fixture was then fabricated and assembled by myself and installed into the Dynatup 8250 apparatus with the aid of Kodi A. Rider. The fixture was then tested using a ½ inch thick foam and carbon fiber sandwich plate at maximum velocity and showed no signs of plastic deformation or fracture failure.