INNOVATIVE ENERGY ABSORBING AND LOAD LIMITING DEVICES BASED ON COMPOSITE TUBES
Open Access
- Author:
- Tiwari, Chandrashekhar
- Graduate Program:
- Aerospace Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- None
- Committee Members:
- Prof Edward C Smith, Thesis Advisor/Co-Advisor
Edward C Smith, Thesis Advisor/Co-Advisor - Keywords:
- composite tubes
energy absorption
load limiting
extension-twist
stitch ripping
foam crushing - Abstract:
- Analytical and experimental studies of innovative load limiting and energy absorbing devices are presented here. The devices are based on composite tubes. They can be categorized in two groups based upon the energy absorbing mechanisms exhibited by them, namely: stitch ripping and foam crushing. The stitch ripping device is composed of two concentric cylindrical composite tubes with opposite angles of fibers. The tubes are stitched together by a thread across the cross section and along the length. The tubes exhibit opposite extension-twist coupling. Upon being loaded axially, the tubes twist in opposite directions. Prior to their failure, the threads prevent relative rotation of tubes. This loads the threads in tension. At certain limit load stitches begin to rip and energy stored in threads gets dissipated. The device is termed as tension-torsion stitch ripping device (TTSRD). The device based on foam crushing as the energy absorbing mechanism is composed of light weight foam core inside a composite tube. The tube is tailored to have a high Poisson’s ratio (>20). Upon being loaded the device experiences large transverse contraction resulting in rapid decrease in diameter. At a certain axial load the foam core begins to crush and energy gets dissipated. This device is termed as crush tube. The devices exhibit variations in force-displacement characteristics, with changes in design and material parameters, resulting in wide range of energy absorption capabilities. Different material systems were analyzed and metrics such as specific energy absorptions (SEAs) and volumetric energy absorptions (VEAs) of the devices were compared. It was found that the TTSRD is capable of providing 2-3 times higher SEA than currently used devices for similar purposes (such as wire bender which has SEA of 3.6 J/g). In addition to this crush tube is capable of providing SEA 4-5 times higher than similar devices.