This research project aims at delaying the onset of interfibre/matrix cracking in multilayer CFRP composites by applying design/manufacturing means, which are in analogy to the concept of prestressed concrete. Two major routes are being studied: Controlled expansion of a composite structure by using an expandable mandrel. Expansion is either done after filament winding, but prior to completion of gelling/curing or on a finished standard wound structure at a temperature above the glass transition point with final release of the expansion loads after cooling down. Stress relief of standard wound structures by submission at elevated temperatures to stresses similar to those experienced in later operation followed by cooling down to ambient temperature prior to unloading.
For certain CFRP structures, precompression of the matrix can be achieved using an expandable mandrel. This leads to an increase in the tolerance stress/strain range as the threshold for interfibre/matrix cracking and thus first ply failure moves toward higher strain values.
Funding SchemeCSC - Cost-sharing contracts