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Development of a Tension Energy Absorber - Progressive Bearing Failure Mechanisms of Composite Bolted Joints

Waimer, Matthias and Schatrow, Paul and Feser, Thomas and Kraft, Harald and Kohlgrüber, Dieter (2016) Development of a Tension Energy Absorber - Progressive Bearing Failure Mechanisms of Composite Bolted Joints. 8th Triennial International Aircraft Fire and Cabin Safety Research Conference, 24.-27. Oktober 2016, Atlantic City, NJ, USA.

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Abstract

This paper deals with experimental investigations on progressive bearing failure mechanisms of composite bolted joints and their integration into a crash design concept. The objective of the presented test program is a crash design for a generic composite transport aircraft fuselage structure that utilizes tension loads in the passenger cross beam for energy absorption. In this design, the passenger cross beams are fabricated from carbon fiber reinforced plastics (CFRP) and kinetic energy shall be absorbed by progressive bearing failure of their bolted attachments. A specific design for a standard bolted joint was developed and experimentally investigated, which provides controlled bearing failure to reliably ensure energy absorption in combination with sufficient structural integrity in a crash event. The concept ensures • controlled direction of bearing failure under various loading conditions (on- and off-axis loading), • a robust stop mechanism to limit the progressive bearing failure to a certain displacement, • steady, progressive failure with non-constraining flow of the debris out of the local crush zone to prevent blockage effects, which may lead to abrupt load increase. In a comprehensive test program on coupon level several design concepts were investigated under quasi-static loading considering the progressive failure mechanisms of one single bolt. This bolt connects two CFRP sheets and is set under regular conditions (pre-stressed). In the shear tests, the bolt shaft is pulled through one of the CFRP sheets leading to significant energy absorption. Different design concepts, including specific notches and modified washers, were tested with the aim to ensure constant load level during the failure process by steady debris outflow that prevents debris blockage effects in the local crush zone in front of the bolt. Subsequently, preferential concepts were tested with a crash relevant dynamic loading rate of v = 2 m/s. The concept was proven on element level using multi-bolt specimens (2-bolt and 4-bolt). On-axis and off-axis loading up to 30° was tested under dynamic loading conditions of v = 0.1 m/s and v = 2 m/s. Further design modifications were investigated that focused on enhanced robustness and an improved connection for the standard operating condition. On this element level, the concept feasibility could successfully be confirmed. Finally, this paper presents application aspects of the tension absorber concept. Crash simulations of a fuselage section are presented that illustrate the potential of energy absorption by utilization of tensile crash loads in the passenger cross beam.

Item URL in elib:https://elib.dlr.de/109054/
Document Type:Conference or Workshop Item (Speech)
Title:Development of a Tension Energy Absorber - Progressive Bearing Failure Mechanisms of Composite Bolted Joints
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Waimer, Matthiasmatthias.waimer (at) dlr.deUNSPECIFIED
Schatrow, Paulpaul.schatrow (at) dlr.deUNSPECIFIED
Feser, ThomasThomas.Feser (at) dlr.deUNSPECIFIED
Kraft, HaraldHarald.Kraft (at) dlr.deUNSPECIFIED
Kohlgrüber, DieterDieter.Kohlgrueber (at) dlr.deUNSPECIFIED
Date:October 2016
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Status:Published
Keywords:transport aircraft, crashworthiness, composite material, bolted joint, bearing failure, progressive failure, energy absorption
Event Title:8th Triennial International Aircraft Fire and Cabin Safety Research Conference
Event Location:Atlantic City, NJ, USA
Event Type:international Conference
Event Dates:24.-27. Oktober 2016
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:fixed-wing aircraft
DLR - Research area:Aeronautics
DLR - Program:L AR - Aircraft Research
DLR - Research theme (Project):L - Structures and Materials
Location: Stuttgart
Institutes and Institutions:Institute of Structures and Design > Structural Integrity
Deposited By: Waimer, Matthias
Deposited On:19 Dec 2016 11:13
Last Modified:19 Dec 2016 11:13

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