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In their service life, fibre reinforced plastics (FRP) face a variety of environmental conditions resulting from natural or artificial factors. These include variable temperature and humidity conditions, energetic radiations such as ultraviolet rays from the sun, and diverse chemical reactants such as liquid in storage tanks and pipes. These factors are always combined and negatively affect the material properties over the time. Therefore, optimized utilization of FRP material requires reliable methods for quantifying, controlling, and predicting environmental effects. This allows for optimal handling of issues related to component design, economic assessment and safety considerations, as well as the technical problems relating to equipment maintenance. Efforts worldwide are devoted to the modelling of FRP environmental degradation. However, modelling efforts have been hindered by the complexity of the process. This analysis presents a comprehensive model of the environmental degradation of FRP and a prediction method. The modelling method consists of a theoretical demonstration based on material science theories. An analytical approach is proposed. It resolves the complexity of the process into only three components: the chemical degradation, the physical degradation, and the stress state modification. A method to represent the real service environment as a constant environment in laboratory is also introduced. Then, the comprehensive model is expressed as a dynamic constitutive equation resulting from the combination of the historical variation in chemical link density and cohesive forces and the stress history of the material. It is shown that: • The average of the chemical and physical degradation as well as its upper and lower limits can be determined in a laboratory, in a constant environment, as exponential functions of the degradation time. • The environmental degradation can be comprehensively measured as a stress relaxation. • Acceleration of the predictive test can be obtained from a modified time temperature shift principle.

The mechanical properties of alumina trihydrate (ATH)-filled epoxy resin at loadings of up to 100 parts by weight ATH per hundred of resin (epoxy and hardener) (pphr) have been investigated. A low peak exotherm, increased Young's modulus and increased critical strain energy release rate (G[sub]IC) and critical stress intensity factor (K[sub]IC) can be achieved by incorporating a dispersion of ATH into an epoxy resin. However, the high filler loadings required for effective fire resistance reduce tensile strength and elongation. Tensile modulus increases with filler loading in line with previous studies and theoretical equations. However, the tensile strength is higher and the ultimate elongation lower than current theories predict. The tensile and fracture process in ATH-filled epoxy follows linear elastic fracture mechanics, but can be considered in two parts. The initiation of a crack occurs from a large critical flaw, either as a large particle or agglomerations of particles. A flaw can also be formed on the application of a tensile load, when large stress concentrations cause localised microcracking of the matrix. The propagation of a flaw requires more energy and is dependent on several possible mechanisms. Shear yielding and associated crack blunting are shown to be the most important mechanisms, whilst minor contributions from matrix microcracking and debonding of ATH particles are possible. The absence of crack pinning in this study is believed to be due to the inherently weak nature of ATH particles. The presence of a 10pphr rubber dispersion in ATH-filled epoxy only increases the values of G[sub]IC and K[sub]IC at low filler loadings. Amine-terminated butadiene acrylonitrile rubber (ATBN)-modified epoxy matrix exhibits little adhesion to ATH and therefore the efficiency of stress transfer between particle and matrix is reduced, diminishing shear yielding.

An extensive study of into the static loading response and low-velocity impact response of plain and stiffened CFRP panels was conducted. The study investigated the impact response of the CFRP panels over a range of impact energies that include incident kinetic energies sufficiently high to cause complete penetration of the panel by the impacting mass. Static tests were also conducted by driving a hemispherical-nosed indentor into the panel up to displacements that resulted in the complete penetration of the panel by the indentor. Results from these tests suggest that the static perforation energy could predict the impact perforation energy with reasonable accuracy. A lumped-parameter mass-spring-damper model that attempted to incorporate the effects of material damage to the panel response was developed. The model was found to be sufficiently accurate in predicting the response of thin panels to static and impact loads up to the critical delamination force threshold. Assessment of the damaged panels through Penetrant-Enhanced X-Ray methods led to the identification of damage transition energy thresholds that differentiate between changes in damage mechanism. The damage transition energy thresholds were found to be constant fractions of the impact perforation energy.

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