No abstract

The energy absorption capability of a composite material is critical to developing improved human safety in an automotive crash. Energy absorption is dependent on many parameters like fiber type, matrix type, fiber architecture, specimen geometry, processing conditions, fiber volume fraction, and testing speed. Changes in these parameters can cause subsequent changes in the specific energy absorption (ES) of composite materials up to a factor of 2. This paper is a detailed review of the energy absorption characteristics in polymer composite materials. An attempt is made to draw together and categorize the work done in the field of composite energy absorption that has been published in the literature in order to better understand the effect of a particular parameter on the energy absorption capability of composite materials. A description of the various test methodologies and crushing modes in composite tubes is also presented. Finally, this paper raises certain design issues by examining the work rate decay necessary to keep the deceleration below 20g during an impact crash.

An amphiphilic block copolymer toughener was incorporated into a liquid epoxy resin formulation and self-assembled into well-dispersed nanometer scale spherical micelles with a size of about 15 nm. The nanosized block copolymer at 5 wt % loading can significantly improve the fracture toughness of cured epoxy thermosets without reduction in modulus at room temperature and with only a slight drop in glass transition temperature. The toughening mechanisms were investigated, and it was found that the 15 nm size block copolymer micelles could cavitate to induce matrix shear banding, which mainly accounted for the observed remarkable toughening effect. Other mechanisms, such as crack tip blunting, may also play a role in the toughening. A discussion of the possible reasons responsible for the observed attractive mechanical property improvements due to the block copolymer modification is given. Implications of the present finding for designing toughened polymers are also discussed.