Characterization of the Quasi-Static Axial Crushing of Multi-Tubular FRP Composite Structures Using Commercially Available FRP Tubes and PU Foam Filling

Abstract The aerospace and automotive industries are inclining towards utilizing materials such as carbon fiber composites to replace conventional heavy metallic materials, which enhances fuel efficiency and structural safety. This experimental investigation fabricated various types of carbon fiber reinforced polymer tubes, Kevlar reinforced polymer tubes and polyurethane foam into multi-tubular composites, exploring their axial crushing characteristics. The investigation revealed that including and varying the internal tubing arrangements in the hollow carbon fiber reinforced tubes significantly improved their load bearing and energy absorption capabilities. In addition, these composite arrangements incorporated polyurethane foam to assess the effects of polyurethane foam (PU foam) fillers on the axial crashworthiness performance. It was found that, in addition to specific energy absorption, polyurethane foam enhanced other mechanical properties, such as peak load, mean load, crushing force efficiency, and overall energy absorption capability of all the compositions. The specific energy absorption factor exhibited variable behavior due to the added weight of the polyurethane foam in the composite tubes. Intermediate carbon composite tubing improved energy absorption, with Carbon based tubes provide competent mechanical performance. Despite its added mass, polyurethane foam filling increased load-bearing capacity but decreased specific energy absorption, impacting the overall efficiency of the carbon composite structure during axial crushing load. The use of braided carbon fiber tubes as inner tubes resulted in the highest enhancement of crushing properties. Moreover, addition of PU foam exhibited improved crashworthiness compared to composites without them.