A pre-compressed, stitch-bonded glass fiber material which is volumised by embedding thermoplastic microspheres. Particularly suitable for wet-on-wet process for producing both stable and light homogeneous laminates at the same time. The excellent characteristics result from the complete impregnation with ca. 40% by volume of the same resin used to laminate the skin layers. This sandwich material which can be laminated substitutes balsa, PVC foam material and other core materials but has the advantage of being able to adjust to the mould three-dimensionally.