SELF-STRESSING FIBER COMPOSITES

A rapid deterioration of civil infrastructure has created one of the major challenges facing the nation and the construction industry today. Since the cost of civil infrastructure constitutes a major portion of the national wealth, the development of new, long-lasting, and cost-effective high-performance construction materials and systems is important for the economic well-being of the United States in the next century. This paper presents a new concept of embedding memory materials (for example, shape memory alloys--SMAs) as muscular fibers in cementitious composites to develop self-inducing prestressing composites. Such composites are capable of changing the level of prestressing throughout the life of the structure without using jacks or other mechanical devices. The paper presents experimental proof of the self-stressing concept in which SMA fibers were used to trigger self-stressing of the composite plates. Matrix prestressing stresses of 50,000 psi (346 MPa) and 85,000 psi (586 MPa) were achieved this way. While the experimental investigation focused on SMAs, the presented analytical investigation shows that other types of memory materials, such as memory polymers, could also be used to manufacture self-stressing composites. The paper provides a simple relationship that can be used to engineer the required properties of such memory materials.