Mechanical Behavior of Beryllium Wire Reinforced Plastic Composites. Part I. Static Mechanical Properties

摘要

Unidirectional and multidirectional composites of five mil diameter beryllium wire combined with an epoxy resin were fabricated and their mechanical behavior in tension, compression, flexure, and shear loading modes determined. The composites possessed good bonding between the filament and matrix. Continuity in the filament and matrix phases was apparently maintained at all stress levels up to failure. In general, the composite stress-strain behavior reflected that of the beryllium reinforcement, with an initial linear relationship followed by decreasing stress-strain rate to failure. The yield strengths of the composites at 0.2% offset strain were 80-90% of the ultimate strengths. The efficiency with which the beryllium reinforcement modulus and strength was translated into composite properties was greater than 80%. The composites failed by plastic deformation sometimes followed by buckling (compression) or fracture (tension). Plastic deformation in a composite may be desirable as a mechanism for redistributing local stress concentrations and increasing the energy required to cause failure. The specific elastic modulus and specific ultimate strength of the beryllium composites were high, but their proportional limits were less than one-third of the ultimate strength. Variation of the moduli with stress above the proportional limit is an important consideration, especially in connection with buckling phenomena. (Author)