Specific energy absorption

Composite stmctural elements have been shown to be capable of high specific energy absorption (SEA) under crash loads through appropriate design and initiation of... 

FairfiiU AH, Hull D. Effects of specimen dimensions on the specific Energy absorption of fibre composite mbes. In ICCM6 6th Int. Conf. Compos. Mater., London 1987. 3.36-45. 

Aerogels are quasi-stable, low-density, three-dimensional assemblies of nanoparticles, which have usually poor mechanical properties. A facile one-pot synthesis of Kevlar-like aerogels based on the reaction of multifunctional isocyanates and carboxylic acids has been reported [57]. The materials exhibit an ultimate compressive strength, a high specific energy absorption, and a thermal conductivity like foamed PS. By a pyrolysis process at 800 °C, the materials can be converted to a porous, electrically conducting carbon with a high surface area. 

Table 13.1 compares the mechanical properties under compression of crosslinked vanadia (X-VO and crosslinked surfactant-templated silica (X-MP4-T045) with other strong materials. For application in armor, the figure of merit is the specific energy absorption, where both crosslinked vanadia and templated silica far surpass even silicon carbide ceramics. 

Material Density (g cm ) Ultimate compressive strength (MPa) Specific ultimate compressive strength (Nmg- ) Specific energy absorption (J g )... 

Material PbCgcm Modulus (MPa) 0.2% Yield strength (MPa) UCS (MPa) (% strain) Specific UCS (Nm g ) Specific energy absorption (Jg- )... 

For characterization of crash worthiness the maximum (peak) force and the mean force are considered. The ratio of peak and mean force (load uniformity) for ideal absorbers is considered to equal 1. The mass specific energy absorption E, expressing the efficiency of the specimen... 

The superior specific energy absorption of composites makes them attractive for crashworthiness (Vaidya, 2011). CFRP crush cones and similar structures can absorb 250 kJ/kg with a thermoplastic resin compared to 120 kJ/kg with a thermoset resin like epoxy, or versus 20 kJ/kg for steel. Crush properties can also be optimized by mixing carbon with other fibres as mentioned in Herrman et al. (2002). 

Table 30.16 Specific Energy Absorption of Different Composites...

---