Measurement of residual strains in boron-epoxy and glass-epoxy laminatesEmbedded-strain-gage techniques were developed and used for measuring strains in composite angle-ply laminates during curing and thermal cycling. The specimens were 2.54 by 22.9 cm eight-ply boron-epoxy and S-glass-epoxy laminates. Unidirectional specimens were used for control purposes. Strain readings were corrected for the purely thermal output of the gages obtained from an instrument quartz reference specimen. The strains measured during the cooling part of the curing cycle were in agreement with those recorded during subsequent thermal cycling, indicating that residual stresses induced during curing are primarily caused by differential thermal expansions of the various plies. Restraint strains were computed for the 0-deg and 45-deg plies of the angle-ply laminates tested, and the residual stresses obtained using the anisotropic constitutive relations and taking into account the temperature dependence of stiffnesses and strains.
Document ID
19760033606
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Daniel, I. M. (IIT Research Inst. Chicago, IL, United States)
Liber, T. (IIT Research Institute Chicago, Ill., United States)
Chamis, C. C. (NASA Lewis Research Center Cleveland, Ohio, United States)