THERMAL EXPANSION BEHAVIOR FOR THE SHORT GLASS FIBER-EPOXY COMPOSITE AND THE SHORT GLASS FIBER-UNSATURATED POLYESTER COMPOSITE

The temperature and the fiber length dependences of the thermal expansion coefficients of epoxy and unsaturated polyester resins reinforced with random-planar orientation of short glass fiber were studied.For both composites, the thermal expansion coefficient of fiber orientation plane increases with increasing temperature. The coefficient of composites is given by the mean value of longitudinal and transverse coefficients for the unidirectional short fiber reinforced composite, the critical fiber length being taken into consideration.The thermal expansion coefficient of composites is known to decrease with increase in the aspect ratio of reinforcing fiber. When the composites are reinforced with random-planar orientation of short glass fiber with 3 times of the mean critical length, the thermal expansion coefficients are almost equal to that of the theoretical value with continuous glass fiber.