Pneumatic strains in woven glass/epoxy composite laminate induced by fluctuating air pressure

Pneumatic strain of composite material is a novel discovery within the field of composite engineering. Ambient air pressure change induces the strain, which is not negligible in comparison with hygrothermal strain and is physically reversible. Previous research has verified that a sudden ambient air pressure change can result in a monotonically increasing or decreasing strain, which always approaches to a plateau value asymptotically. The final strain is proportional to air pressure change. The pneumatic strain can be predicted via the theory based on the Fick's diffusion law. In this work, the same theory was modified to predict the pneumatic strains induced by multi-step air pressure change and fluctuating air pressure. The theoretical predictions matched very well with the experimental data. The theory can be used to describe the pneumatic behavior of composite structures serving in the environment that has fluctuating air pressure such as the composite components of aircraft, pressure vessels and pipes. (C) 2002 Elsevier Science Ltd. All rights reserved.