Damage Evolution and Progressive Failure in Composite Material Highway Guardrails

The evolution of damage and the progressive failure of prototype highway guardrails, constructed of thermoset plastic /E-glass composite materials, is described. The composite material guardrails are being studied as potential replacements for conventional steel w-beam guardrails. The objective of this phase of the study was to investigate progressive failure of composite cross-sections as a means of dissipating energy in the guardrail when subjected to a vehicular impact. The prototype rails were connected to standard steel blockouts and tested quasi-statically under displacement control. The blockouts were designed to allow local rotation of the blockouts and large deflection of the guardrail sections so as to develop a tension field in the rail following the initial “local damage phase.” The results of the static tests on the composite rails were compared with those of a standard steel w-beam tested in the same fixture. From the quasi-static tests the evolution of the local damage and the progressive failure in the composite prototype rails could be observed. Observed changes in failure modes at different load levels could be correlated with discontinuities in the load-deformation data obtained during the testing. A study of the energy absorbed during the initial flexural damage phase (prior to the tension field developing in the rail) revealed the relative contribution of this phase to the overall energy absorbed during the progressive failure of the rail. From this preliminary study it appears that composite material guardrails may be able to dissipate more energy in the initial flexural phase than conventional steel w-beams.