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A shock absorber characterised by fixed-to-hinged transforming joints and inward-folding composite tubes was demonstrated for the first time. Polymethacrylimide foam can be filled into the composite tube to enhance energy absorption. A pair of shock absorbers were installed in the subfloor structure as stanchions. The shock absorber, inclined at an angle to the impact direction, was joined to the subfloor structure with five fasteners arranged so that one is in the centre and the others around it. The five fasteners bore a static load during normal operations. During the crash, the eccentric load is exerted on the shock absorber as the crushing of the composite tube; then, the surrounding fastener is served, with the central fastener left as a pin. Hence, the fixed joint is transformed into a hinged joint, making the shock absorber only subject to an axial load, and a large crush ratio for the absorber is available. A method to calculate the crash load of a subfloor structure was demonstrated. Experiments were conducted using a drop tower, which verified the schematic and crash-load calculations. The results also show that the specific energy absorption of the composite tube filled with foam is improved. The proposed schematic of the subfloor structure has the potential for use as an aircraft cargo floor. [ABSTRACT FROM AUTHOR]

This paper describes the design and testing of a shock absorber with an inward-folding composite tube that can be used as a structural component in its normal working state. Although more energy can be absorbed when the hollow of the tube is filled with composite debris, a higher load relative to the initial peak load will be produced. A variable structure based on two inclined energy absorbers was then proposed, and impact tests used to verify the reaction load calculation for two models experimentally. Results indicate that the variable structure had a greater compression ratio and a flatter load curve, demonstrating its potential for use in the struts of an aircraft cargo floor. [ABSTRACT FROM AUTHOR]