In-plane compression modulus and strength of Nomex honeycomb cores

The stress-strain response and deformation mechanism of a range of Nomex honeycomb cores tested under in-plane compression has been examined experimentally. The cores with a thin wall displayed extensive bending deformation of the cell walls inclined to the horizontal (loading is vertical) and failed in bending. The cores with thicker walls failed by a shear-type instability of the cells indicated by tilting of vertical cell wall segments. The failure strain decreased with increasing core density. The modulus and compressive strength of the core were compared to micromechanical predictions. Normalized modulus and strength values varied between the various cores. The average modulus and strength results allow backing out of the modulus and bending strength of the Nomex paper. The results were in reasonable agreement with published tensile test results and composite micromechanics.

Establishment and application of soil hydraulic erosion model based on GIS and USLE model

Soil erosion is the most common form of soil degradation, which is the main problem of soil environmental destruction worldwide. Based on the USLE and GIS remote sensing inversion and superposition analysis technology, this study simulated and calculated soil hydraulic erosion in Fangshan World Geological Park, China in 2011, 2012 and 2013, analyzed its spatial-temporal dynamic changes, and explored the key points of soil erosion control in the study area. The results show that (1) The main erosion occurred at 25°-35° steep slope and 400-800m height, which accounted for more than 30% of the total soil erosion in all the three years. (2) The average erosion modulus and erosion amount in 2012 were significant higher than that in 2011 and 2013 at each slope grade, shown that the soil erosion of 2012 is influenced by natural disaster.With the increase of slope grade, the average modulus also increased.

Sustainable Water Responsive Mechanically Adaptive and Self-Healable Polymer Composites Derived from Biomass

New synthetic biobased mechanically adaptive composites, responding to water and having self-healing property, were developed. These composites were prepared by introducing plant-based cellulose nanofibrils (CNFs) at 10, 20, and 25% (v/v) concentration into a biobased rubbery poly (myrcene-co-furfuryl methacrylate) (PMF) matrix by solution mixing and subsequent compression molding technique. The reinforcement of CNFs led to an increase in the tensile storage modulus (E’) of the dry composites. Upon exposure to water, water sensitivity and a drastic fall in storage moduli (E’) were observed for the 25% (v/v) CNF composite. A modulus reduction from 1.27 (dry state) to 0.15 MPa (wet state) was observed for this composite. The water-sensitive nature of the composites was also confirmed from the force modulation study in atomic force microscopy (AFM), revealing the average modulus as 82.7 and 32.3 MPa for dry and swollen composites, respectively. Interestingly, the composites also showed thermoreversibility and excellent healing property via Diels-Alder (DA) click chemistry using bismaleimide as a crosslinker, when the scratched samples were heated at 120 °C (rDA) for 10 h and then cooled down to 60 °C (DA) followed by room temperature. The healing efficiency was obtained as about 90% from the AFM 3D height images. Thus, the composites exhibited dual stimuli-responsive behavior as mechanically adaptive water sensitive polymers with water as the stimulus and self-healing polymer using bismaleimide as an external stimulus. Therefore, this study provides guidance and new frontiers to make use of composite materials based on biopolymers for various potential smart and biomedical applications.

Laboratory Evaluation of Gradation Improvement of Marginal Materials for Foamed Bitumen Stabilisation

Foamed bitumen stabilisation is an attractive technology for increasing the use of marginal materials in pavement construction and rehabilitation. However, by their very nature, marginal materials do not meet the prescriptive requirements of many standard specifications. Consequently, performance-related evaluation is required. For foamed bitumen stabilised marginal materials, the cured and saturated moduli are common performance-related parameters that are also used for characterisation during structural pavement design. In this research, the indirect tensile moduli of three foamed bitumen stabilised marginal granular materials were compared to the modulus of a standard or premium material, in both cured and saturated conditions, after 3, 7 and 14 days of accelerated laboratory curing. The results indicated that the magnitude of granular material marginality was not related to the stabilised material modulus. Furthermore, the gradations of the two most marginal materials were improved by blending with another granular material and the improved marginal materials were also stabilised and tested. The gradation improvement had a variable effect on the stabilised material modulus, with the average modulus increasing by more than 20%. The modulus increase associated with the gradation improvement was related to the basis and magnitude of granular material marginality, with the saturated modulus of the most plastic marginal material increasing by the greater amount after improvement. It was concluded that foamed bitumen stabilisation is a particularly effective treatment for marginal granular materials. Furthermore, when used in combination with gradation improvement, the resulting foamed bitumen stabilised material can perform similarly to standard materials, based on cured and soaked modulus values. However, to allow the use of foamed bitumen stabilised marginal materials in pavement construction, specifications must be more performance-related and the current limits on plasticity and gradation must be relaxed.

Researches Regarding the Compression of the Films Polymers in Composite System

This paper presents experimental research results obtained from testing the compression of polymer matrix composites. The four types are analyzed by thin layers of polymer composite material of various thicknesses were subjected to the test of mechanical compression. The analyzed samples were obtained by reinforcing the siloxane rubber with FeSi powder and stretching the mixture on the metallic mesh (PM), as well as stretching the simple siloxane rubber, without reinforcing agent on the metallic mesh. The mathematical modeling of the experimental results obtained on the LFM 30kN compression tester, Walter & Sai AG was performed using the Excel program. Establishment of material was based on regression analysis performed later. The modulus of elasticity of the samples was determined according to the deformation range 0.1 ÷ 0.3%, corresponding to the maximum correlation coefficient resulting from the regression of the experimental data. Following the compression analyzes it was found that in the case of simple siloxane rubber (S) without filling, the average modulus of elasticity decreases from 80 MPa to 39 MPa for the siloxane rubber laying on the metallic mesh. For the composite material (siloxane rubber with FeSi powder addition) noted SF, the value of the module is 81, and in the case of the laying composite (siloxane rubber reinforced with silicon iron powder filler on the metallic mesh, noted PMSF), the value of the module decreases to 31 MPa. We conclude that the addition of silicon iron powder leads to an increase in the elasticity of the siloxane rubber, and its reinforcement with the metallic mesh leads to a decrease in the elasticity modulus of the siloxane rubber, as well as of the siloxane rubber reinforced with the iron powder.

Analysis of relations between the moduli of elasticity in compression, tension, and static bending of hardwoods

Accurate estimation of average modulus of elasticity in compression parallel to the grain (Ec0) is of paramount importance for rational sizing of timber structures, given the use of this property in the estimation of stability of compressed parts (ultimate limit state, ULS) and in calculation of excessive strains (serviceability limit state, SLS). In Brazil, if values cannot be experimentally determined, ABNT NBR 7190 (1997) allows for estimation of Ec0 through relations to average modulus of elasticity both in tension parallel to the grain (Et0) (Ec0 = Et0) and in bending (EM) (Ec0 = EM/0.90). This research aimed to access the efficiency of these relations by testing 30 tropical wood species. The analysis of variance results showed that Ec0 and Et0 were statistically equal. However, Ec0 and EM/0.90 were not statistically equal, and the method of least squares resulted in a coefficient of 0.98, which was 8.89% higher than the one suggested by ABNT NBR 7190 (1997) and close to 1, thus, validating the results of ANOVA, which pointed on the equivalence between Ec0 and EM (Ec0 = EM). As an alternative to simplified equations of the standard, two-parameter regression models were used. The geometric model with R² = 91.67% proved to be the model of best fit, which demonstrated that Ec0 could be calculated as a function of EM.

Development of a Composite Material Based on Polymers Polydimethylsiloxane and Polytetrafluoroethylene Use in Human Prosthetic Coatings

The purpose of this study is the development of a composite material composed of a main layer of polydimethylsiloxane (PDMS) and a reinforcement of polytetrafluoroethylene (PTFE), to be used later in human prosthesis coatings. A mass ratio of the main layer consisting of PDMS:Tetraethyl orthosilicate (TEOS):Di-n-butyl tin dilaurate (DBTL) in the range of 33:1:0.5; 25:1:0.5; 10:1:0.5, and the mass ratio of the composite material (PTFE:PDMS) with a range was evaluated of 1:9; 1:1; 2:3. Obtaining the following results: Tensile strength of 0.085 MPa based on the ratio of 33:1:0.5 - 1:9 and 0.59 MPa with respect to the ratio of 10:1:0.5 - 2:3, evidencing an increase in tensile strength by decreasing the weight of PDMS and increasing the weight of PTFE. On the other hand, the composite material obtained is hydrophobic, insoluble in ethanol and water, has a cross-linking percentage of 98.74 % and 99.66 % respectively, also has a minimum permeance of 5.24x10-7 (g Pa-1 s-1 m-2). With which it is concluded that the treatment whose properties resemble the human skin is the combination 10:1:0.5 - 1:1 that allowed to obtain an average tensile strength of 0.66 MPa, average modulus of elasticity of 6.56 MPa, similar to the dermis of a 43 year old person.

A Biomechanical Investigation of Collagen, Platelet-Rich Plasma, and Mesenchymal Stromal Cells on the Achilles Tendon in a Rat Model

This study aims to biomechanically compare four different treatment methods for repair enhancement in Achilles tendon rupture in rats: collagen, collagen and platelet-rich plasma (PRP), collagen and mesenchymal stromal cells (MSC), and a combination of collagen, platelet-rich plasma and mesenchymal stromal cells (CPM) at one and two week healing periods. This study included ninety Lewis rats weighing approximately 200–300 g. Ten rats were used as donors for MSC and PRP. For the remaining eighty rats, the right leg was completely transected 6 mm proximal to the calcaneus bone, suture repaired, wrapped in CollaTape (CoTa), and then closed. An injection of PRP, MSC, or PRP and MSC was given at the wound site to the applicable groups. After one or two weeks recovery time, the rats were sacrificed and both Achilles tendons were removed. The left tendons were used as virgin tissue controls. It was found that the maximum stress at failure, the total strain energy, the average modulus of elasticity, and the elastic strain energy all increase significantly from one week to two week recovery time. However, there was no statistical difference between treatment groups in any of the mechanical properties.

Nanoindentation of Aluminum Single Crystals: Experimental Study on Influencing Factors

Results from nanoindentation of aluminum single crystals deliver valuable information as model systems for understanding technical aluminum alloys. The effect of the crystal orientation and the azimuthal indenter orientation on indentation hardness and modulus was studied by Vickers indentation (max. load 10 mN) on single crystal surfaces with (100), (110), and (111) orientations. The average indentation hardness varied, depending on the crystallographic orientation, by 1.8%. The anisotropy of the elastic modulus (1.1% of the average modulus) is lowered (indentation averaging effect). This is predicted by explicit approximation of the contact problem (conical indenter, orthotropic material). It was found that indentation hardness and modulus vary periodically with the azimuthal indenter orientation on (100)- and (110)-oriented surfaces (relative amplitude of 1.8% for indentation hardness and 2.6% of the modulus). This is attributed to the combined effect of the indenter geometry and crystal symmetry. For the first time, this effect was quantified for aluminum single crystals.

Determination of Strength Properties of Energy Plants on the Example of Miscanthus × Giganteus, Rosa Multiflora and Salix Viminalis

Energy from biomass accounts for 70% of all renewables used for heat and electricity production. Such a significant share of biomass determines the need for the investigation of their mechanical properties, as most of the lignocellulosic material requires cutting, chipping or milling before its utilization for energy purposes. Therefore, the knowledge about cutting resistance, bending stiffness, and impact strength of the energy plants is very important. The values of these parameters are used in the proper selection of shredding machines and their elements, wrapping nets or determination of power demand during raw material conversion. This paper presents the results of research on the mechanical properties of selected energy plants. The scope of the research included three different plant species: Miscanthus × giganteus, Rosa multiflora, and Salix viminalis, investigated in terms of cutting resistance, bending stiffness and impact strength of stalks. The results showed that the average stalk cutting resistance for the rotation speed of 4200 RPM was 0.17 N·mm−2 for the Miscanthus × giganteus, 0.15 N·mm−2 for the Rosa multiflora and 0.2 N·mm−2 for the Salix viminalis. Meanwhile, for a rotation speed of 3200 RPM, the cutting resistance amounted to 0.15 N·mm−2 for Miscanthus × giganteus, 0.16 N·mm−2 for Rosa multiflora and 0.18 N·mm−2 for Salix viminalis. For the impact measurements, the Salix viminalis exceeded 40 J·mm−2 of absorbed energy. Meanwhile, the average impact strength value for the Rosa multiflora was 0.53 J·mm−2 and for the Miscanthus × giganteus was 0.22 J·mm−2. The bending stiffness of Miscanthus × giganteus at an average modulus of 3.44 GPa was 1.1 N·m2 for the basal zone, 0.78 N·m2 for the central zone, and 0.72 N·m2 of the apical zone. For the average Young’s modulus of 0.19 GPa, the bending stiffness of the Rosa multiflora reached a value of 0.64 N·m2 for the basal zone, 0.23 N·m2 for the central zone, and 0.28 N·m2 for the apical zone. The Salix viminalis, with an average modulus of elasticity of 0.23 GPa, achieved bending stiffness in the basal zone of 0.99 N·m2, the central zone 0.33 N·m2, and the tip zone 0.38 N·m2. This research makes it possible to expand our knowledge in the field of biomass processing and construction of agricultural machinery with higher processing efficiency.