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The issues concerning the prediction of changes in properties of polymer materials as a result of adding reinforcing fibers are currently widely discussed in the field of polymer material processing. This paper aims to present strengths and weaknesses of composites based on polymer materials strengthened with fibers. It touches upon composite cracking at the junction of a matrix and its reinforcement. It also discusses the analysis of changes in properties of chosen materials as a result of adding reinforcing fibers. The paper shows improvement in the strength of polymer materials with fiber addition, which is extremely important, because these types of composites are used in the aerospace, automotive and electrical engineering industries.

Comparing the properties of matrix strength with fiber properties is practically impossible. Thus, fiber tensile strength and composite tensile strength shall be compared (González et al., 2011): tensile (glass fiber GF) = 900 [MPa], elongation ΔL≈ 0; yield point (polyamide 66) = 70−90 [MPa], elongation Δ[%] = 3,5-18; tensile (polyamide 66 + 15% GF) = 80-125 [MPa], elongation Δ[%] ≈ 0; tensile (polyamide 66 + 30% GF) = 190 [MPa], elongation Δ[%] ≈ 0; yield point (polyamide 6) = 45-85 [MPa], elongation Δ[%] = 4-15; tensile (polyamide 6 + 15% GF) = 80-125 [MPa], elongation Δ[%] ≈ 0; tensile (polyamide 6 + 30% GF) = 95-130 [MPa] elongation Δ[%] ≈ 0. Comparison of properties of selected polymers and composites is presented in Tables 1−10 and Figures 1 and 2. The measurement methodology is presented in detail in the paper Kula et al. (2018). The increase in fiber content (to the extent discussed) leads to the increase in yield strength stresses and hardness. The value of yield strength for polyamide with the addition of fiberglass grows gradually with the increase in fiber content. The hardness of the composite of polyamide with glass balls increases together with the increase in reinforcement content. The changes of these values do not occur linearly. The increase in fiber content has a slight impact on density change (the increase of about 1 g/mm³ per 10 per cent).

The use of polymers as a matrix allows to give composites features such as: lightness, corrosion resistance, damping ability, good electrical insulation and thermal and easy shaping. Polymers used as a matrix perform the following functions in composites: give the desired shape to the products, allow transferring loads to fibers, shape thermal, chemical and flammable properties of composites and increase the possibilities of making composites. Fiber-reinforced polymer composites are the effect of searching for new construction materials. Glass fibers show tensile strength, stiffness and brittleness, while the polymer matrix has viscoelastic properties. Glass fibers have a uniform shape and dimensions. Fiber-reinforced composites are therefore used to increase strength and stiffness of materials. Polymers have low tensile strength, exhibit high deformability. Polymers reinforced by glass fiber have a high modulus of elasticity and therefore provide better the mechanical properties of the material. Composites with glass fibers do not exhibit deformations in front of cracking. An increase in the content of glass fiber in composites increases the tensile strength of the material. Polymers reinforced by glass fiber are currently one of the most important construction materials and are widely used in the aerospace, automotive and electro-technical industries.

The paper presents the test results for polyethylene composites with 25 per cent and 50 per cent filler coming from recycled car carpets of various car makes. The tests included using differential scanning calorimetry, testing material hardness, material tensile strength and their dynamic mechanical properties.

Drawing on socio-cognitively orientated leadership studies, this paper aims to contribute to our understanding of host country employees’ (HCEs) negative perceptions of successive expatriate leadership by exploring how their memories of shared past experiences affect these perceptions. Contrary to previous work which tends to focus on HCEs’ attitudes towards individual expatriates, the authors shift attention to successive executive expatriate assignments within a single subsidiary.

The paper is based on an intrinsic case study carried out in a Polish subsidiary of an American multinational pharmaceutical company which had been managed by four successive expatriate General Managers and one local executive. The authors draw on interview data with 40 HCEs. Twenty-one semi-structured interviews were conducted with staff who had been managed by at least three of the subsidiary’s expatriate leaders.

The authors demonstrate how transference triggered by past experiences with expatriate leaders as well as HCEs’ implicit leadership theories affect HCEs’ negative perceptions of expatriate leadership and lead to the emergence of expatriate leadership schema.

To the best of the authors’ knowledge, this is the first study that explores the role of transference and implicit leadership theories in HCEs’ perceptions of successive executive expatriate assignments. By focussing on retrospective accounts of HCEs who had been managed by a series of successive expatriate leaders, our study has generated a more nuanced and contextualised understanding of the role of HCEs’ shared past experiences in shaping their perceptions of expatriate leadership. The authors propose a new concept – expatriate leadership schema – which describes HCEs’ cognitive structures, developed during past experiences with successive expatriate leaders, which specify what HCEs believe expatriate leadership to look like and what they expect from it.