The effect of a circular hole on the tensile strength of neat and filled rigid PUR foams

• Rigid PUR foams with polyols from recycled PET are produced and characterized.
• The effect of a hole on the tensile strength of rigid PUR foams is studied.
• Finite fracture mechanics is applied to predicting the reduction in foam strength.
• A reasonable accuracy of strength prediction is achieved by the FFM.

In order to elucidate the effect of stress concentration on the tensile strength of rigid polyurethane (PUR) foams, specimens with open circular holes and different ratios of hole diameter to specimen width were tested in tension. The reduction in the net-section strength of the specimens with a center hole ranged from 1% to 18% for neat foams and from 18% to 28% for foams produced from a nanoclay-filled PUR. The finite fracture mechanics approach, based on simultaneous application of the strength and fracture mechanics criteria of failure, yielded a reasonably accurate prediction of foam strength in the presence of stress concentration.