Failure mechanism in SMC subjected to alternating stresses

• Published in: Journal of materials science 1990-09, Vol.25 (9), p.4087-4097
• Main Authors: VON BERNSTORFF, B, EHRENSTEIN, G. W
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Mechanical properties; Physical properties; Polymer industry, paints, wood; Properties and testing; Technology of polymers
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/BF00582486

Failure mechanisms in randomly reinforced sheet moulding compounds subjected to fatigue testing were studied by relating the changes in characteristic mechanical properties to microscopic changes in the material. The compositions of the SMC were roughly 30% unsaturated polyester or vinyl ester resin, 30% glass fiber rovings, and 40% finely ground calcium carbonate. It was demonstrated that various mechanisms take place simultaneously to an extent that depends on the local microstructure and strength and that the collective interplay of these mechanisms is responsible for failure. As damage progresses, a uniform pattern of cracks is formed in the matrix, and Mode II fibre /matrix-interfacial failure occurs. The mechanisms concerned can be explained by calculating the forces transmitted between the fibres and the matrix. It was observed that different load amplitudes gave rise to equivalent damage patterns in the material. In light of this fact and with the aid of the failure mechanisms identified, a method has been devised, by means of which the fatigue life of SMC exposed to alternating loads of any given amplitude can be estimated. Graphs, Photomicrographs. 15 ref.--AA