Experimental and numerical analysis of foam-filled composite structures subjected to axial crushing

Crash components in transport vehicles are significant structures for the application of the composite materials due to their high energy absorption capacities. Even better energy absorption values can be achieved by foam filled crash components due to the interaction effect between foam core and structure wall. In this thesis study, axial crushing behavior of composite circular tube structures and foam filled composite circular tube structures were examined experimentally and numerically. Experimental tests on crash specimens were performed as quasi-static axial crushing tests. Numerical analyses carried out in ABAQUS/Explicit Finite Element Analysis software. Main goals of the study are to investigate composite tubular structures and foam filled structures axial crushing behavior by energy absorption and specific energy absorption and to simulate the axial crushing behavior of the specimens accurately. Empty composite tube specimens used in the study were manufactured from plain weave fabric carbon fiber composite with three different diameters of Ø30mm, Ø40mm and Ø50mm. Empty tubes as well as polyurethane (PU) foam filled and syntactic foam filled composite tubes were tested experimentally. Effect of the crushing by using external crush plugs on axial crushing characteristics of empty tubes were also investigated in this study. Crushing characteristics, energy absorption values and specific energy absorption values of various specimens were discussed. Experimental tests were simulated in ABAQUS finite element software by modelling composite materials by using built-in VUMAT subroutine "ABQ_PLY_FABRIC" for intra-laminar damage, and cohesive surface method for inter-laminar damage. Built-in *CRUSHABLE FOAM material model was used to model PU foams. Experimental test results and numerical simulation results were evaluated with load displacement curves and specific energy absorption (SEA) displacement curves. At the end of the study, numerical simulations exhibited coherent results to experimental studies and it is found out that specific energy absorption of the foam filled tubes is lower than empty tubes even the absorbed energy is higher.