Cure shrinkage effects in epoxy and polycyanate matrix composites [report]

G.P. Spellman
1995 unpublished
A relatively new advanced composite matrix, polycyanate ester, was evaluated for cure shrinkage. The chemical cure shrinkage of composites is. difficult to model but a number of clever experimental techniques are available to the investigator. In this work the method of curing a prepreg layup on top of a previously cured laminate of identical ply composition is utilized. The polymeric matrices used in advanced composites have been primarily epoxies and therefore a common system of this type,
more » ... erite 3501-6, was used a s a base case material. Three polycyanate matrix systems were selected for the study. These are: Fiberite 954-2A, YLA RS-3, and Bryte Technology BTCy-1. The first three of these systems were unidirectional prepreg with carbon fiber reinforcement. The Bryte Technology material was reinforced with E-glass fabric. All systems were processed similarly although each required certain variation in cure cycle profile a s recommended by the manufacturer. Details of the processing technique are fully described. The technique used to evaluate cure shrinkage results in distortion of the flatness of an otherwise symmetric laminate. The first laminate is cured in a conventional fashion. An identical layup is cured on this first laminate. During the second cure all constituents are exposed to t h e same thermal cycles. However, only the new portion of t h e laminate will experience volumetric changes associate with matrix cure. The additional strain of cure shrinkage results in an unsymmetric distribution of residual stresses and an associated warpage of t h e laminate. The resulting distortion was measured using conventional mechanical methods. The baseline material, Fiberite 3501 -6, exhibited cure shrinkage that w a s in accordance with expectations. Cure strains were -4.5E-04. The YLA RS-3 material had cure strains somewhat lower a t -3.2E-04. The Fiberite 954-2A cure strain w a s iv -1.5E-04 that is 70% lower than the baseline material. The glass fabric material with the Bryte BTCy-1 matrix did no result in meaningful results because the processing methods were not fully compatible with the material. 8
doi:10.2172/219366 fatcat:bmvlbbrsnjeongfdtvoltrmpfy