G. Marino

Bio: G. Marino is an academic researcher. The author has contributed to research in topics: Glass transition & Thermosetting polymer. The author has an hindex of 1, co-authored 1 publications receiving 40 citations.

Residual stresses in thermoplastic composites—A study of the literature—Part I: Formation of residual stresses

Abstract: Continuous fibre reinforced thermoplastic composites are increasingly applied in aircraft structures. These high-performance thermoplastic matrices need processing at high temperatures; therefore, thermal residual stresses arise due to the mismatch in coefficients of thermal expansion between the fibres and the thermoplastic matrix. Since residual stresses are inherently present in virtually all composite materials and influence the properties of the composite structures significantly, it is of utmost importance that the residual thermal stresses are taken into account in both design and analytic modelling of composite structures. In order to understand the effects of residual stresses and find ways to decrease their magnitude or use them to our advantage, the factors responsible for the residual stress build-up need to be understood. This first part of a literature review discusses these factors, focusing on thermoplastic composites, and in particular the material properties of their constituents and processing parameters governing stress build-up.

Residual stresses in thermoplastic composites - a study of the literature. Part III: Effects of thermal residual stresses

Abstract: This paper is the third part in a series of review papers on residual stresses in thermoplastic composites. The first two parts were dedicated to the formation of thermal residual stresses and experimental techniques to detect these stresses, respectively. This third paper discusses the effects that thermal residual stresses have on the material properties of thermoplastic composites. Composite laminates as well as composite structures were considered. Residual stresses were found to affect the composites’ matrix-dominated, mechanical and durability properties, as well as to inflict damage and dimensional instability. Several mechanisms to relieve thermal residual stresses are proposed.

Physical aging in polymers and polymer nanocomposites: recent results and open questions

Abstract: Physical aging is a ubiquitous phenomenon in glassy materials and originates from the fact that they are generally out-of-equilibrium. Due to the technological and fundamental implications, this phenomenon has been deeply investigated in the last decades especially in glassy polymers. Here we provide a critical review of the latest hot debated themes in the field of physical aging in polymers and polymer nanocomposites. We first summarize the fundamental aspects of physical aging, highlighting its relationship with the polymer segmental mobility. A review of the methods employed to monitor physical aging is also provided, in particular those probing the time dependent evolution of thermodynamic variables (or related to) and those probing the (quasi)instantaneous polymer segmental mobility. We subsequently focus our attention on the two following debated topics in the field of physical aging of polymers: (i) the fate of the dynamics and thermodynamics of glassy polymers below the glass transition temperature (Tg), i.e. the temperature below which physical aging occurs; (ii) the modification of physical aging induced by the presence of inorganic nanofillers in polymer nanocomposites. With respect to the former point particular attention is devoted to recent findings concerning possible deviations from the behavior normally observed above Tg of both dynamics and thermodynamics deep in the glassy state. Regarding the effect of the presence of nanofillers on the rate of physical aging, the role of the modification of the polymer segmental mobility and that of purely geometric factors are discussed with particular emphasis on the most recent advances in the topic. The modification of the rate of physical aging in other nanostructured systems, such as polymer thin films, is discussed with particular emphasis on the analogy in terms of a large amount of interface with polymer nanocomposites.