Does the interphase control the transverse modulus of unidirectional GFRP?

In the present work, the influence of the fibre treatment on the transverse stiffness of glass/epoxy unidirectional laminates is discussed. The transv erse modulus of UD-plates with different fibre treatments was determined by the transverse tension test and by vibration tests with holography and an identification procedure. It will be shown that a significant influence of the fibre treatment (interphase) can be observed if the transverse modulus is determined by tension tests. If the transverse modulus is determined by non-destructive testing with vibration tests, including a mathematical iden tification procedure, no significant influence of the fibre treatment can b e observed. This indicates that the results of transverse tension tests sho uld be used very carfully to describe the influence of the interphase on th e transverse modulus of unidirectional reinforced plates. It is recommended to use some additional (non-destructive) testing, e.g. vibration tests.