Mechanical strain with radiation degradation

Above a certain degree of crosslinking, strain at break and impact strength decrease again, and the plastic becomes hard and brittle. Radiation-chemical degradation also causes a decrease in mechanical properties with increasing radiation... 

The mechanical properties, fiacture stress, fiacture strain, yield stress, and modulus, were measured (67) for doses up to 100 Mrads. Fracture strain was found to increase with dosage but shear yield strength decreased. Decreases averaging roughly 50% were noted for the other properties. Therefore, it is evident that the -radiation produces a predominance of chain scission over crosslinking in the epoxy. It was concluded that irradiation does not have much effect on the graphite fibers but that it degrades mechanical properties of the epoxy matrix. 

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