Experimental work

Abstract

The first part of the chapter on experimental work covers the validation of the Puck criteria. This extensive work has verified qualitavely and quantitatively the results both on fracture limits and fracture angle. In addition, the fracture hypotheses of Puck have been validated as the correct physical basis of the fracture criteria. Great effort has not only been put into the validation of Puck's fracture criteria, but also on the determination of degradation curves for the elastic properties of embedded UD-layers being damaged by IFF. In the second part of the chapter this work is presented in detail. Both for GFRP and CFRP the degraded Young's modulus E_⊥ and shear modulus G_⊥∥ have been determined for all crack densities and corresponding stress exposure f_{E, IFF}. The major Poisson's ratio remains uneffected by IFF. The degradation curves are in good approximation valid for all laminate lay-ups independent of the position of the cracked layer within the laminate. The curves can also be used to verify or calibrate other degradation models. The degradation curves are in general valid as long as the effected layer is not under transverse compression (as long as σ₂ ≥0). Under compression, the crack surfaces are pressed on each other and the degradation of stiffness is less significant. For this case the degradation has been investigated, too. The experimentally found degradation curves have also been validated by additional experiments as well as by numerical studies.