JOURNAL OF COMPOSITE MATERIALS Article Structural study and thermal behavior of composites: Polyamide 66/glass fibers: The reinforcement ratio effect on the kinetics of crystallization Azzedine Makhlouf 1,2 , Abdelheq Layachi 1,3 , Imane Kouadri 1 , Ahmed Belaadi 1,4 and Hamid Satha 1 Abstract The present research aims at studying the kinetics of non-isothermal crystallization of the polyamide 66 matrix and its composites with the presence of a glass fiber load. To achieve that goal, the non-isothermal crystallization of polyamide 66 has been studied by means of DSC. The ratio of tested reinforcement varies from 7% to 50% of glass fiber in mass. The modeling, by the theories of Jeziorny and those of Mo, has allowed us to study the influence of adding this reinforcement, as well as the variation of the rate of cooling, on the kinetics of crystallization of the composites in question, which has been manifested by a remarkable change in the nucleation mechanism of the polyamide 66 matrix. Regarding the reinforcement effect, the incorporation of the glass fibers load into the polyamide 66 matrix has caused the appearance of exothermic peaks in a higher temperature range and that for all the working materials. Finally, the results showed that the Mo model is the most suitable for the study of polyamide 66/glass fiber crystallization kinetics. Keywords Polyamide 66, glass fibers, differential scanning calorimetry, kinetics of crystallization Introduction Composite materials made from polyamides reinforced with glass ﬁbers (GFs) are gaining ground in the innovative materials market thanks to their good mech- anical, thermal and electrical properties, especially in the automotive and industries provision of sports and leisure materials. Polyamide 66 (PA66) has good appli- cations in cars because it has better mechanical proper- ties (rigidity, resistance to wear and creep, etc.). These properties help to improve safety and comfort in vehi- cles. In addition, PA 66 exhibits excellent short-term thermal resistance because of its high melting tempera- ture of 260  C. 1 The mechanical properties of the composite material (PA66/GF) depend on both the properties of the glass ﬁbers and those of the organic matrix, in addition to the ability to transfer the stresses through the ﬁber/matrix interface. These properties of the composite, are inﬂu- enced by the mechanical strength of the interface (G/ matrix). 2–8 And depend on the injection conditions such as design and molding temperature. 9–12 During the manufacture of short ﬁbers, the decisive step in the process is the process of cooling including solidiﬁcation. The properties of using a composite material depend not only on the mass characteristics of the two basic constituents (polymer matrix and ﬁbrous reinforce- ment), but also on the quality of the interfacial zone. In some cases, the matrix may be modiﬁed in the vicinity of the ﬁbers with the formation of an interphase with a structure which is diﬀerent from that of the bulk matrix. 13 During the preparation of a thermoplastic 1 Laboratoire des Silicates, Polyme `res et Nanocomposites, Universite ´ du 8 Mai 1945, Alge ´rie 2 De ´partement de Ge ´nie Industriel, Universite ´ Abbe `s Laghrour, Alge ´rie 3 Institue des Sciences et Techniques Applique ´es (ISTA), Universite ´ des Fre `res Mantouri Constantine 1, (ISTA), Alge ´rie 4 De ´partement de Ge ´nie Me ´canique, Universite ´ 20 Aout 1955 Skikda, Alge ´rie Corresponding author: Abdelheq Layachi, Universite ´ 8 Mai 1945, Guelma De ´partement des Sciences de la Matie `re, Guelma 24000, Algeria. Email: abdelhak2416@live.fr Journal of Composite Materials 0(0) 1–15 ! The Author(s) 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0021998319883913 journals.sagepub.com/home/jcm