This article presents a review of the major fatigue models and life time prediction methodologies for fibre-reinforced polymer composites, subjected to fatigue loadings. In this review, the fatigue models have been classified in three major categories: fatigue life models, which do not take into account the actual degradation mechanisms but use S-N curves or Goodman-type diagrams and introduce some sort of fatigue failure criterion; phenomenological models for residual stiffness/strength; and finally progressive damage models which use one or more damage variables related to measurable manifestations of damage (transverse matrix cracks, delamination size). Although this review does not pretend to be exhaustive, the most important models proposed during the last decades have been included, as well as the relevant equations upon which the respective models are based. This review article contains 141 references.

Embedded optical fibre sensors are considered for structural health monitoring purposes in numerous applications. In fibre reinforced plastics, embedded fibre Bragg gratings are found to be one of the most popular and reliable solutions for strain monitoring. Despite of their growing popularity, users should keep in mind their shortcomings, many of which are associated with the embedding process. This review paper starts with an overview of some of the technical issues to be considered when embedding fibre optics in fibrous composite materials. Next, a monitoring scheme is introduced which shows the different steps necessary to relate the output of an embedded FBG to the strain of the structure in which it is embedded. Each step of the process has already been addressed separately in literature without considering the complete cycle, from embedding of the sensor to the internal strain measurement of the structure. This review paper summarizes the work reported in literature and tries to fit it into the big picture of internal strain measurements with embedded fibre Bragg gratings. The last part of the paper focuses on temperature compensation methods which should not be ignored in terms of in-situ measurement of strains with fibre Bragg gratings. Throughout the paper criticism is given where appropriate, which should be regarded as opportunities for future research.

This paper presents the experimental investigation on the progressive deformation behaviour of uni-directional pultruded composite tubes subjected to an axial impact load. Pultruded square and circular profiles with glass-polyester and glass-vinylester combinations were used for this study. Two types of triggering profiles were incorporated to investigate the effect of triggering on the energy absorption. All above combinations were investigated for three different impact velocities (9.3, 12.4 and 14m/s). The crushing peak and mean load characteristics of the composite tubes with different triggering profiles and their progressive failure modes are presented. To measure the impact velocity and the impact force, a contactless method using digital image correlation technique was adopted. The effects of the geometry profile, triggering, strain rate and the type of resin on energy absorption of the composite tubes were studied in detail.KEYWORDS: Specific energy absorption; Triggering mechanism; Crushing; Progressive failure; Composite tubes IntroductionA great deal of research and development has been carried out in the past decades to design safer automobiles. Out of the factors considered for safety criteria, the crashworthiness has attracted significant attention due to its multiple functions. The functions of the crashworthiness structures are to (i) absorb energy, (ii) keep the occupant compartments intact and (iii) ensure tolerable deceleration levels for driver and passengers during the crash event. To meet the above functions, the automobile industry is focused on the design architecture and materials used to produce crashworthiness. As a result, different forms of the energy absorbers [1,2] and combinations of high strength metal alloys are used for crashworthiness structures. The focus on new innovative materials which yield superior strength to weight ratio [3] has been increased in order to meet the future stringent crashworthiness norms and to enhance the fuel economy target.On the other hand, there is a considerable amount of experiments [4][5][6][7] conducted on composite material to assess the energy absorption. It is a well-known fact that one can

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