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During the fiber fracture of unidirectional composite a distribution of stress around the neighbored fibers happens, this mechanism is called the local redistribution efforts. Referring to the "shear lag" method, the researches wanted to predict the stress concentration in the surrounding area of broken fibers as well as the longitudinal resistance of the unidirectional composite which presents a fiber breaking. The goal of this paper is to develop a new probabilistic model of unidirectional composite plate to calculate the stress concentration at the broken fibers and their neighboring fiber intact. The "shear lag" method has been generalized to see the broken fibers interference on the stress concentration factor variation of surrounding sound fibers.

The present work reports an experimental study on the thermal and mechanical properties of hybrid composites obtained from Petiole Date Palm Fiber (PDPF)/Glass fiber (GF) as reinforcement and vinylester resin (VE). In order to improve the fiber/matrix adhesion, palm fibers were alkali treated with 5% NaOH solution for 24 h–72h. SEM and ATR-FTIR analysis revealed that the 48 h treatment of PDFP with NaOH solution led to rough fiber surface. Vacuum assisted resin transfer molding (VARTM) system was used to produce four hybrid composites (30PDPF/0GF, 20PDPF/10GF, 10PDPF/20GF and 0PDPF/30GF) where the weight ratio of total fiber reinforcement was kept 30%. The treated palm fibers were arranged as a nonwoven mat and placed between woven glass fabrics. Tensile, flexural, dynamic mechanical thermal analysis (DMTA), and thermogravimetric (TGA) were carried out to evaluate the performance of the hybrid composites. The flexural strength and modulus for pure PDPF composite were found to be 60 MPa and 3.87 GPa respectively. Addition of 20%wt glass fiber led an increase in the thermal stability and an enhancement in the tensile and flexural strength by 71.72% and 74.51%, respectively compared to pure PDPF composite. However, the incorporation of 10% of PDPF increases the damping factor from 0.2 for the composite glass/VE to 0.54 for the hybrid 10PDPF/20GF. According to findings of this study, PDPF based composites can be used as non-structural parts in automotive and boat industries.

In this work, an experimental investigation was proposed for the evaluation the wear resistance of hybrid polymer composite inter-layer of Petiole date palm fiber (PDPF) and glass fiber (GF). In order to enhance the interfacial of hydrophobic fibers (PDPF) and hydrophilic (Vinylester resin), chemical treatment was proposed based on 5% NaOH for 48 h. Besides, the glass fiber (woven) was used in order to increase the specific stiffness and the dimensional stability of specimens. The manufacturing of four hybrids specimens was done using a VARTM process [(30PDPF/0GF), (20PDPF/10GF), (10PDPF/20GF) and (0PDPF/30GF)]. The wear characteristics were evaluated at a sliding distance of (1000 m), sliding velocity (1.7 m/s) and applied loads (20 and 40 N). Scanning electron microscopy was performed on both treated alkali fiber and worn surfaces of hybrid specimens to evaluate the surface modification and wear mechanisms, respectively. The adding of glass fiber to PDP fibers was advantageous on the wear resistance, where it improved the wear resistance of 30PDPF/0GF around 190 and 310% as compared to (20PDPF/10GF) and (10PDPF/20GF), respectively. The adding of loads was disproportional to wear resistance. The SEM of worn surfaces showed debonding and bending of fibers, and fragmentation, fiber broken, and deformation on the resinous regions. In the end, the hybridization by 20% of glass fibers exhibits a high wear resistance relative to its nature (partially bio-friendly) and price.