The promotion and the popularization of the micro concrete tiles in any locality obligation with a will of durable development pass by a standard of quality, which is based on the results of scientific and technical research taking account of local specificities. This work proposes to study the porosity of the micro concrete by micro structural analysis. From this study, it comes out that the variation of porosity compared to the ratio of the fine gravels (s/(s + g)) is decreasing. Indeed more the granular ratio increases less low is the density of pores of material. The decrease of porosity according to the granular rate is not infinite; it tends towards a minimum starting from a rate of fine gravel close to 50%. The results obtained justify well the ratio of fine gravel practised by tileries.

The ply elastic constants needed for classical lamination theory analysis of multi-directional laminates may differ from those obtained from unidirectional laminates because of three dimensional effects. In addition, the unidirectional laminates may not be available for testing. In such cases, full-field displacement measurements offer the potential of identifying several material properties simultaneously. For that, it is desirable to create complex displacement fields that are strongly influenced by all the elastic constants. In this work, we explore the potential of using a laminated plate with an open-hole under traction loading to achieve that and identify all four ply elastic constants ( E 1 , E 2 , ν 12 , G 12 ) at once. However, the accuracy of the identified properties may not be as good as properties measured from individual tests due to the complexity of the experiment, the relative insensitivity of the measured quantities to some of the properties and the various possible sources of uncertainty. It is thus important to quantify the uncertainty (or confidence) with which these properties are identified. Here, Bayesian identification is used for this purpose, because it can readily model all the uncertainties in the analysis and measurements, and because it provides the full coupled probability distribution of the identified material properties. In addition, it offers the potential to combine properties identified based on substantially different experiments. The full-field measurement is obtained by moiré interferometry. For computational efficiency the Bayesian approach was applied to a proper orthogonal decomposition (POD) of the displacement fields. The analysis showed that the four orthotropic elastic constants are determined with quite different confidence levels as well as with significant correlation. Comparison with manufacturing specifications showed substantial difference in one constant, and this conclusion agreed with earlier measurement of that constant by a traditional four-point bending test. It is possible that the POD approach did not take full advantage of the copious data provided by the full field measurements, and for that reason that data is provided for others to use (as on line material attached to the article).

Liquid resin infusion (LRI) processes are promising manufacturing routes to produce large, thick, or complex structural parts. They are based on the resin flow induced, across its thickness, by a pressure applied onto a preform/resin stacking. However, both thickness and fiber volume fraction of the final piece are not well controlled since they result from complex mechanisms which drive the transient mechanical equilibrium leading to the final geometrical configuration. In order to optimize both design and manufacturing parameters, but also to monitor the LRI process, an isothermal numerical model has been developed which describes the mechanical interaction between the deformations of the porous medium and the resin flow during infusion.(1,2) With this numerical model, it is possible to investigate the LRI process of classical industrial part shapes. To validate the numerical model, first in 2D, and to improve the knowledge of the LRI process, this study details a comparison between numerical simulations and an experimental study of a plate infusion test carried out by LRI process under industrial conditions. From the numerical prediction, the filling time, the resin mass and the thickness of the preform can be determined. On another hand, the resin flow and the preform response can be monitored by experimental methods during the filling stage. One key issue of this research study is to highlight the changes in major process parameters during the resin infusion stage, such as the temperature of the preform and resin, and the variations of both thickness and fiber volume fraction of the preform. Moreover, this numerical/experimental approach is the best way to improve our knowledge on the resin infusion processes, and finally, to develop simulation tools for the design of advanced composite parts.

A novel direct approach to detect the resin flow front during the Liquid Resin Infusion process under industrial environment is proposed. To detect the resin front accurately and verify the results, which are deduced from indirect micro-thermocouples measurements, optical fiber sensors based on Fresnel reflection are utilized. It is expected that the results derived from both techniques will lead to an improvement of our understanding of the resin flow and in particular prove that micro-thermocouples can be used as sensors as routine technique under our experimental conditions. Moreover, comparisons with numerical simulations are carried out and experimental and simulated mold filling times are successfully compared.

The resin transfer molding (RTM) process is one of manufacturing processes of composite structures. Various industries such as aerospace and automotive have widely used the RTM process in order to manufacture composite structures. The manufacturing procedures are simply divided into 5 steps: 1. Placing fiber preform on a lower mold 2. Closing a upper mold 3. Injecting resin 4. Curing 5. Demolding. The third step, which is injecting resin, should be carefully designed in order to make products without any defects. However, the designing of the stage is often time-consuming and expensive because various variables to control the mold filling exits as injection pressure, number of injection gates and vents, etc. Numerical simulations of the mold filling stage have been used by the solution to reduce the design time and cost. Through numerical simulations, designers can predict whether defects such as air voids exist or not in the mold after filling. In RTM process simulations, the issue is how to treat the moving interface between resin and air. The representative methods to treat the moving interface are distinguished by moving and fixed grid approaches. The moving grid approaches is necessary to re-mesh a computational domain before every time steps. The frequent re-meshing may cause low accuracy of RTM process simulations, especially when the interface shape is complex. Therefore, fixed grid approaches has more popularly used by researchers in RTM process simulations because the re-meshing is unnecessary. The frequently used numerical methods in fixed grid approaches are finite element method with control volume approach, control volume finite element method, and nonconforming finite element method. However, these methods also have some drawbacks: to roughly describe the moving interface and to inaccurately approximate the pressure in regions intersected by the interface. The alternative numerical methods should be considered in order to overcome the drawbacks and increase accuracy of RTM process simulations. The traditional numerical methods do not intuitionally catch interface positions in the elements intersected by the interface. In addition, although the gradient of pressure in elements intersected by the interface is discontinuous, the traditional methods do not reflect the discontinuous character. In our research, extended finite element method combined with level set method was applied to simulate the RTM process. The moving interface was captured by level set method. The pressure calculation was performed by extended finite element method. The whole computational procedures of our approach are shown in Figure 1. Figure 1. Computation procedures The interface of complex shape, by multiple injection gates and complex geometry mold, was well-described in our simulations. The pressure was more accurately approximated by extended finite element method. For verification of our code, our computation results were compared experimental results as well as analytic results. The results proved that our approaches gave high accuracy in RTM process simulations.

Microcracking of polymer matrix composites reinforced by multiaxial multi-ply stitched carbon preforms submitted to cyclical purely hygrothermal loading is analyzed. The laminates are manufactured by liquid resin infusion (LRI). The stitching induces deviations in fibre layout and creates openings which become resin-rich regions after the resin infusion. The interaction between resin-rich regions and microcracks induced by the hygrothermal cycles was investigated by 2D metallographic micrography and X-ray microtomography. Specific microcracking process was found to occur in this type of material. The occurrence of cracks was quantified and the morphology of the 3D crack network studied. The nature of the stitching yarn and the size of the diamond-shaped resin-rich regions were identified as having a major influence on laminate microcracking after ageing.

Homogeneous low voltage electron beam irradiation (HLEBI) improved the elasticity indicated by both flexural modulus (E-f) and the maximum slope value ((d sigma/d epsilon)(max)) of the bending stress strain curve of carbon fiber reinforced thermoplastic polyetheretherketone (CFRTP) composite sheets with 0.50 mm thickness, although the penetration depth estimated was from 0.14 to 0.21 mm on both side surfaces. HLEBI remarkably enhanced both E-f and (d sigma/d epsilon)(max). The E-f at middle cumulative probability (P-E) of 0.50 for CFRTP irradiated at 0.30 MGy (kJg(-1)) was 3.3 GPa, which was 27% higher (2.6 GPa) than for CFRTP before irradiation. Moreover, (d sigma/d epsilon)(max) a at middle cumulative probability (P-E = 0.50) was more than 4.9 GPa for CFRTP irradiated at 0.30 MGy. The interfacial friction force, as well as the strengthening of both carbon fiber and polyetheretherketone probably contributed to the HLEBI effects to enhance both E-f and (d sigma/d epsilon)(max) in the CFRTP. [doi:10.2320/matertrans.MBW201005]

As one type of Liquid Composites Mouhling （LCM） processes, Liquid Resin Infusion （LRI） has become recognized as a manufacturing of structural polymer - based composites for the aerospace industries. In order to improve our outstanding of the LRI process and control it well, this paper deals with the problem of obtaining more inside information by an experimental method, such as the deformation of the preform stacking and the resin flow. For getting internal measurements during the infusion process with little disruption, an optical fiber Bragg grating sensor （FBG）, a micro -thermocou- pie and a micro - strain gage have been embed at strategic locations of the preform. Bragg wavelengths on FBG proportionally shift with temperature and strain variation, so we propose a simple coupling measurement method between FBG and micro - thermocouple to obtain directly the average deformation and the local temperature of the preform together. Resin takes 550 s to fill the prefrom stacking and during this infusion stage, the prefrom stacking is on compressive condition. In the curing stage （75 min）, the prefrom stacking is compressed maximum, but this compressive effect is relaxed partly during the following stage （cooling stage）. Finally, these results can also verifier with the measurements of the strain gage. The article will present details of the technique as well as preliminary results.

Resin Transfer Molding (RTM) process is widely used in the industries of transport. For the design of the manufacturing process, it is necessary to simulate the resin flow in the mold so as to avoid the formation of air voids which could cause critical defects in the product. One of the important points to track the resin flow in the mold is to provide accurate approximation at the moving resin flow front.

The compression molding process is a manufacturing process in which precharges containing chopped fibers are compressed in a mold. In many cases, SMC (Sheet Molding Compound) in the form of a thin sheet is used. At the design step, the fiber state of the structure to produce is assumed to have a homogeneous fiber volume fraction and an isotropic fiber orientation at anywhere on the structure. This fiber’s state changes due to the flow characteristics produced during the filling process. The mechanical properties of the final product are determined dominantly by this fiber state. Consequently, this non-uniform distribution of the fiber state induced by the fiber separation or the change of fiber orientation during the compression molding process generates non-uniform mechanical properties of the final product.

The main goal of the present study is to optimise the precharge conditions such as the precharge location and dimensions that give significant effects on the mechanical performance of composite structures manufactured by the compression moulding process. As preliminary step of optimisation, we developed a manufacturing simulation program to predict the fibre volume fraction and fibre orientation. And coupled with this simulation program and a structural analysis program, a genetic algorithm (GA) is implemented to optimise the precharge conditions. The penalty function method and the repair algorithm are modified for handling constraints. The repair algorithm is applied to a symmetric structure and an arbitrary shape structure to find optimal precharge conditions.

The micro-structure of polymer matrix composites reinforced by multi-axial multi-ply stitched carbon preforms and manufactured by liquid resin infusion is analyzed. The stitching induces deviations in fibre placement and creates openings which become resin-rich regions after the resin infusion. Characterization of the size and shape of the resin-rich regions of composites with different stitching yarn size and tightness and various stacking sequences has been performed by 2D metallographic micrography and X-ray microtomography. The resin-rich region volume was estimated at roughly 3.0±0.5% of the material volume. The resin-rich regions constitute about 9% of the resin in the entire composite, whose fibre volume fraction is close to 65%. X-ray microtomography was successfully used to characterize the 3D microcracks created by hygrothermal fatigue.

Optical fibre Bragg gratings (FBG) provide accurate and non-intrusive strain and temperature local measurements. FBG sensors can be embedded into fibrous preforms to monitor the flow and the cure of the resin and deliver real-time information on the ongoing process. The paper concentrates on the utilisation of the strain-induced birefringence of the FBG to derive information on the effective stressstrain state of the composite at the end of the process cycle (Vacher 2004, Optical fiber sensors to monitor the processing and the mechanical characterization of composites. PhD thesis). During the cooling phase, the reflection spectrum from the FBG splits into two peaks because of the birefringence of the glass fibre owing to the residual stress. The paper shows that this effect can be utilised to estimate the residual stress and strain in composites manufactured by Liquid Composite Moulding technologies. The birefringence effect arising from the cooling of a [06,903]S CFRP laminate is first characterised, and then the determination of the strains along the principal axes inside the laminate is completed by modelling the local stressstrain state because of the interaction of the optical fibre and its environment within the framework of orthotropic thermo-elasticity and the Classical Laminated Plate Theory.