Fibre prestressed polymer-matrix composites: a review

Abstract

This article reviews the literature studies based on improving the mechanical properties of fibre-reinforced composites using fibre-prestressing method. The idea is characterized by pretensioning the fibres either elastically or viscoelastically prior matrix curing. The beginnings of the studies in this field were focused on reducing fibre waviness and breaking the weaker fibres by pretensioning the fibres to a relatively high stress level prior moulding process. In the last three decades, the concept of fibre prestressing had been developed to include its ability to reduce the effect of undesired residual stresses existence accompanying manufacturing process of fibre-reinforced composites. The main advantage of fibre prestressing method is to generate a desired and controlled residual stress state within the matrix in order to obstruct the initiation and propagation of cracks. Various techniques of fibre prestressing have been reviewed to show their scope of applications, developments and limitations. Therefore, the findings drawn from this review can be used for further studies in the field of fibre prestressed composites in order to select the most suitable methodology and develop it to fit the manufacturing process requirements towards a production of high-performance composites without a considerable additional cost.

Development of beneficial residual stresses in glass fiber epoxy composites through fiber prestressing

“…The presence of compressive residual stress within the matrix increases the tensile capacity of the composites and reduces the initiation and propagation of cracks. 9,13 In addition, reducing fiber waviness in prestressed composites due to applying tensile stress to the fiber during curing of the matrix results in fibers within composites that can carry the transferred load to the matrix instantly and simultaneously which increases the tensile properties of composites. 13,27 The results also indicated that the prestressed composites which were prepared by using the estimated optimum FPL achieved the highest tensile strength and beyond the optimum FPL, the tensile properties start to decline.…”

“…Producing compressive residual stress within the cured matrix up to a certain value is beneficial and can enhance the mechanical properties of composites. 13 The optimum compressive residual stress can be determining by the following steps: (1) preparing prestressed composites with fixed fiber volume fraction by using different FPLs, (2) performing the required mechanical testing and determining the optimum FPL which is corresponding to the highest properties, and (3) substituting the optimum FPL in equation (9) …”

Process Induced Defects in Liquid Molding Processes of Composites

“…In addition, the presence of microcracks increases the composites vulnerability to moisture absorption and chemical attacks, ultimately reducing their durability and mechanical performance (Guloglu et al,2016;Mostafa et al, 2017). Microcracks can form during cure when the induced residual stresses are greater than the resin yield strength.…”

“…Building on this effort, a number of researchers adapted these advances in numerical simulation methods to the cure step of LCM processes, often following the impregnation (Khoun and Hubert, 2010;Michaud et al, 2002;Mostafa et al, 2017). In addition to optimizing cure, researchers aim to reduce residual stresses and limit the occurrence of cure induced defects (Baran et al, 2017;Dong et al, 2004;Khoun and Hubert, 2010;Mostafa et al, 2017;Nielsen et al, 2013;Ruiz and Trochu, 2006).…”

“…In addition to optimizing cure, researchers aim to reduce residual stresses and limit the occurrence of cure induced defects (Baran et al, 2017;Dong et al, 2004;Khoun and Hubert, 2010;Mostafa et al, 2017;Nielsen et al, 2013;Ruiz and Trochu, 2006). For instance, Ruiz and Trochu (2006) developed a multi-criteria optimization algorithm to optimize an objective function that incorporates conflicting goals such as minimization of residual stresses, maximization of the final degree of cure and reduction of cycle time, as well as avoiding thermal degradation of the matrix.…”