Thermal-expansion stresses in reinforced plastics

Abstract

Failure of adhesive bonds is attributed to boundary stress concentrations. An analysis of the causes of internal-stress concentrations in rigid adhesive layers leads to the conclusion that stress concentrations can be eliminated in many cases by matching the coefficients of thermal expansion of the component parts. A stress-equilibrium formula for calculating the thermal-expansion coefficients of mixtures involves the density, modulus of elasticity, coefficient of thermal expansion, and proportion by weight of the ingredients. Illustrations of the application of the derived formula include lead-antimony and beryllium-aluminum mixtures, phenol-formaldehyde resin and glass-fiber mixtures, and plastic plywoods. The thermal-expansion coefficients of a number of pure and reinforced plastics are reported. Bonds obtained when thermal coefficients are matched are stable over a wide t emperature range. 3. Application to mixtures of phenol-formaldehyde resin and glass fibers ______ ___ _ V. Detlilrmination of coefficient~ of thermal expansion of plastics ___ __ __ ___ __________________ 1. Factors affecting thermal-coefficient measurements of plastics _ _ _ _ _ _ _ _ _ _ _ _ 2. Results of thermal-expansion measurements for plastics ____ ___ ____________ VI. Conclusions