against r¯ for the Alcan, Alporas, Alulight and PVC
foams: we find that Jss:sUTSl : 1 for the Alporas,
Alulight and PVC foams whereas Jss:sUTSl : 0.2 for
the Alcan foam. The reduced value of Jss:sUTSl for
the Alcan foam is consistent with the observation that
the critical opening Du, at which the bridging traction
drops to zero in the deep notch tests, is given by
Du:0.2l for the Alcan foam. By comparison, the
bridging traction drops to zero at Du:l for the Alporas,
Alulight and PVC foams.