Experimental investigation of the buckling of polymeric composites during simultaneous high heat flux exposure and compressive loading

A cone calorimeter is modified to study the effect of simultaneous high heat flux surface heating and compressive loading on the failure time of fiberglass-reinforced vinyl-ester matrix polymeric composites. Compressive loading of test samples during heat exposure is achieved by using a specially designed mechanical loading fixture that mounted directly below a radiant cone heater. Using specimens with a heated length of 74 and 100 mm, the effect of surface heat fluxes from 25 to 75 kW/m² and compressive loads from 3.5 to 10.5 MPa on failure time and failure mode is examined. For an intermediate heat flux level of 50 kW/m², the time-to-failure of the composite varied from 404s at 3.5 MPa to 131s at 10.5 MPa. All test conditions cause catastrophic failure instability, even at compressive stresses as low as 3.5 MPa. Measurement of the axial and transverse displacements of specimens shows the existence of a thermal bendin moment during the combined thermal and mechanical loading. In addition to experimental results for the relationship between heat flux, compressive load and failure-time, details of the experimental procedure, including the modifications made to the cone calorimeter to allow simultaneous mechanical loading are discussed.