Although there are several differences between the human hair and fibers, they are both examined due to their similar appearance and their common usage. Hairs have proteins in their structure whereas fibers can have cellular or other kinds of structures like polymers as well. In addition, when hairs begin their periodical Anagen and Telogen growth, they posses special microscopically properties. Hair and fiber evidences are not the only indicators of tussle between suspect and victim, however they have paramount importance in reconstructing the crime scene and proving fight and locating it. This article focuses on the examination of hairs and fibers in forensic analysis and its recent advancements.

Cotton pulp cellulose and butyl methacrylate were used as the main raw materials to synthesize cellulose/butylmethacrylate graft polymer (Cell-g-PBMA) via homogeneous ATRP method, after which the graft polymer was dissolved in N, N-dimethylacetamide to prepare a spinning solution, and the novel oil-absorbent Cell-g-PBMA graft polymer fibers were spun by wet-spinning method. The morphology of the polymer fibers before and after oil absorption was analyzed using a high-powered microscope and scanning electron microscope and the saturated oil absorption rate as well as buoyancy recovery of the fiber products were also studied. The results showed that Cell-g-PBMA polymer fibers had a rough surface and exhibited a void network structure that was specific to oil-absorbent materials. The saturated absorption rates of the Cell-g-PBMA polymer fibers for crude oil, vegetable oil, dichloromethane and diesel were 96.5, 78.7, 38.4, and 27.2 g/g, respectively, which were about 3-6 times that of a commercial polypropylene sorbent. The Cell-g-PBMA fibers also displayed excellent oil/water selectivity and high buoyancy recovery in the clean-up of oil over water. Its excellent oil absorbency demonstrated oil absorbent characteristics of both traditional oil-absorbing materials and synthetic oil-absorbing resins, rendering it an excellent fibrous oil-absorbent material.

Residual stresses are formed in composite materials due to mismatch of the coefficient of thermal expansion (CTE) of the components. In polymer matrix composites, reinforced with glass fiber, the CTE of polymer is usually much higher than that of glass fiber. The CTE mismatch of two phases in composite causes the formation of residual stress at the fiber-matrix interface that in turn results in premature fiber-matrix debonding. In this work, the mismatch of fiber and matrix has been compensated through fiber pre-tensioning during the curing of the epoxy resin. It is shown that application of 4 MPa tension is able to remove residual shear stress remained at the fiber-matrix interface of the composites.

Natural fiber-based composites are applied in many structural engineered products from civil constructions to automobile manufacturing due to the properties such as low density, high aspect ratio, biodegradability and ease to work. During the past decades such composites have been thoroughly studied for their mechanical properties and failure behavior and their properties compared with those of synthetic fiber-based composites. Other properties, such as the thermal behavior of natural fibers and composites, have also been studied because they determine the performance of their products possible. It deals with the effect of temperature on adhesive curing, effect of high temperature and fire damage during fabrication. Further, the thermal properties have equal importance in structural applications such as temperature transfer from end to end, load capacity at specific temperature, material behavior and dimensional stability at high temperature. In this respect the isothermal and non-isothermal thermogravimatric analyses are discussed and the improtance of glass transition temperature is studied during prepapration of composites to ensure their ultimate properties. Although there are several works that have been done on thermal behavior, especially thermogravimetric analysis of natural fibers and their composites, there is no review article available specially focused on natural fiber-based composites, hybrid composites, and nanocomposites. The aim of this review was to focus on the advances in the comprehension of thermogravimetric behavior of natural fibers and compare the effect of natural fibers as reinforced materials in polymer composites.

The advent of metal fibers has led to the development of different fiber-reinforced composite systems via different manufacturing methodologies. Utilizing metal fibers as a single reinforcement can create completely new materials with unique physical structures and a synergistic effect on many properties. Steel, aluminum, titanium, and copper are examples of metal fibers used in industries such as aerospace, marine, automotive, and structural applications. Moreover, the possibility of combining various material systems (metal fibers - traditional fibers) to create hybrid composites allows for unlimited variation in cost and performance. In general, metals are available in the form of sheets as metal fiber metal laminate (FML), or as metal fibers in the form of fine wires, and mesh fibers. Investigation of fine wires and mesh fibers is still limited in the literature compared to the sheet metal form. Therefore, this work focuses on reviewing the processing techniques, properties, and applications of fine wires and mesh metals. In this paper, the application, methods of production, and several types and forms of metal fiber were described in detail. Moreover, the properties and applications of metal fibers reinforced polymer composite materials have been reviewed. The application of metalized fibers and the hybridization of metal fibers with synthetic and natural fibers reinforced polymer composites are also reviewed. To conclude, the potential of fine wires and mesh fiber forms, which are partially explored, seems to have excellent mechanical, thermal, and other material properties. Steel fiber is the most common metal fiber used due to its cost-effectiveness, availability in different forms, and high performance despite its heavy weight.

The objective of this study was to investigate the effect of combination of impact modifier on the mechanical properties and morphology of cellulose fiber polypropylene (PP) and high density poly ethylene (HDPE) composites. The impact modifier was ethylene-propylene-diene monomer (EPDM) for PP and ethylene vinyl acetate (EVA) for HDPE and fibers were of alpha cellulose and wastepaper. The elastomer (modifier) was mixed with composite at 5, 7.5 and 10% by weight and the fillers were mixed with PP at 35% and HDPE at 30% by weight. The results have indicated that the notched impact strength, elongation-at-break and bending strains have increased with the inclusion of elastomer, but the tensile strength, bending strength and modulus of elasticity have decreased. The impact modifier, however, did not affect the hardness. The fibers enhanced the tensile strength, bending strength, hardness and modulus of elasticity but decreases were noticed for the impact strength, tensile and bending strains. In fact the highest impact strength was obtained by adding 10% elastomer to the composites, and the highest value for tensile strength, bending strength, hardness and modulus of elasticity were attributed to the absence of elastomer (except the pure polymer).

Increasing growth of using PET bottles has effected made some impacts on different methods of improving their recycling processes. One of the most important feasible methods for this purpose is mechanical recycling. In this research, PP/PET blend fibers with different percentages of PET, in two groups including recycled and virgin PET, were prepared by melt spinning method and their properties have been compared. Testing in this study has been included tensile test, optical microscopy (OM) and scanning electron microscopy (SEM). On the basis of tensile test, tensile strength of fibers with recycled PET is lower than fibers including virgin PET but their elongation-at-break shows higher values. According to OM and SEM micrographs, in both of these groups including virgin and recycled PET, a lack of continuity is observed in moderate percentage. In general the results show that samples with recycled PET have comparable properties with ones including virgin PET.

At first step polymer optical fibers (POFs) are used in short distance for optical data transmissions. At second step SiO2 nanoparticles were prepared by sonochemical-assisted method. Finally silica nanoparticles were added to polymer matrix to prepare polymer based nanocomposites. Most of the POF applications are in the medical and electrical devices. There are several methods for fabrication of POFs, description of which are given in this paper. We have designed a special co-extruder system for fabricating POF. The POFs fabricated by this device are very homogeny and their core and cladding have good viscidity.

Blown bitumen (110/10) was mixed with heavy vacuum slops (H.V.S), 60/70 penetration grade bitumen and recycled isotactic polypropylene (iPP) at different levels. The resulting resins were used to impregnate non-woven poly (ethylene terephthalate) fibers to form composites. The modulus and penetration grade of the resulting bituminous resins were determined. It was found that these bituminous resins drastically affect the modulus of the composites formed by low-Young’s modulus fibers such as polyesters. Consequently, interactions between resin and fibers and the correlation length of asphalthenes (in absence of iPP) and interdiffused coalescence and segregated network of asphalthenes (in presence of iPP) result in a non-linear behavior of composite’s modulus. The behavior of the composites with or without iPP is controlled by resin toughness and resin interactions with the fiber through the viscosity. Comparison of the experimental composite modulus data with the theoretical modulus data revealed that the Takayanangi’s model best predicts the behavior of these composites. The adjustment factors of this model were reported and proposed as an indication of fiber-resin interaction. It was also found that the modulus of fibers is affected by toughness, viscosity and the iPP content of the bituminous resin.