The needs of lightweight and customizable structural materials instigate researchers to conductrnrigorous materials characterization, with particular attention toward failure mechanisms andrnsafety standards, and to study the materialsâ€™ development. Furthermore, the currently availablernstructural and semi-structural composite materials made up of fiber-reinforced plastic, that arernpresently considered to keep the environmental regulations, require multidimensionalrnexamination and analysis because of its heterogeneous nature a non-isotropic behavior.rnConsequently, this research aims to improve the knowledge on specific lightweight material andrnto contribute the confidence that toward their use in spite of its poor nature and suspicious to fail,rnfocusing on some fundamental material properties, such as interlaminar and intralaminarrnbehaviors. The research started from failure characteristics and mechanisms, followed by thernanalysis of the modifications adopted to enhance its structural properties in advanced level, andrnfinally report the adopted experimental characterization procedures and discuss the mainrnfindings.rnThe first part of the study has been focused on composite materials with special targets ofrnenhancement and the structural behavior of these materials was experimentally characterized.rnThe material was manufactured with a plain-woven S-glass fiber-reinforce plastic. The materialrnmodification was obtained by adding nanoparticles to the matrix; therefore a nano-modifiedrncomposite was developed by the appropriate combination of epoxy and nanoclay familyrnparticles, Cloisite 20B. Thus, the fundamental experimental work included the effect of nanoclay,rnCloisite 20B inclusion on the mechanical behavior of a woven type glass fiber reinforced plasticrn(GFRP) composite. Specifically, the study examined the effect of nanoclay, added with variousrnweight percentages, on the tensile, compressive strengths, and modulus of elasticity of GFRP inrnboth weft and warp directions. Results showed that depending on the warp and weft directions,rnthe inclusion of nanoclay, Cloisite 20B, altered the mechanical behavior of GFRP. The advancedrninvestigations focus on the interlaminar characteristics of the material. In this work, the effect ofrnmeticulous nanoclay, Cloisite 20B, inclusion on the interlaminar fracture toughness glass fiberrnreinforced plastic composite was investigated using careful experimental procedure. Afterwardsrnthe study moved to the fracture mechanics behavior, with particular reference to the mode-Irninterlaminar behavior. Tests were conducted based on a double cantilever beam (DCB) specimenrnusing the specific American Society of Testing Materials standard (ASTM D5528). Results showed that the inclusion of nanoclays improved the interlaminar fracture toughness of thernGFRP composite in the range of 12.65% and 54.07% relative to pristine, with progressivernpercentage increment of the nanoclays weight percentage content (from 0.5 to 2%). Therefore,rnthe dissemination of this experimental research results contributes to overlook a betterrnunderstanding of nanoclay fillers and their contribution to mechanical behaviors; this can lead torna better design of novel structural composites. Moreover, it guides how Cloisite fillers contributernto improve the delamination resistance with this special composite material having a betterrnretardant flame propagation property that can be relevant for some structures.rnThe second part dealt with lightweight materials that are intended for the vehicle /automotivernindustry. The intralaminar behavior of the two types of materials, which were supplied by tworninternational companies, was investigated. The fundamental behavior, impact, and specialrnstructural application studies of these two types of innovative materials were examined, oncernagain with particular attention toward the impact response and the fracture nature of thesernmaterials. The first material type is semi impregnated micro sandwich structure (SIMS) and it isrnmanufactured with two specific reinforcing fibers (carbon and glass). The other material belongsrnto the glass mat thermoplastic (GMT) family that has also two types: the conventional GMT andrnthe GMT modified by adding unidirectional fibers (GMT-UD) to stiff the structure. For thosernmaterials, the intralaminar fracture and the nature of the crack behavior were experimentallyrninvestigated using compact tension specimen test. The intralaminar fracture toughness of eachrnmaterial was determined along with crack propagation behavior. As a result, the output of thisrnresearch fills the gaps and it can contribute to having a full picture of the GMT and SIMSrnmaterials.