Experimental characterisation of textile compaction response: A benchmark exercise

This paper reports the results of an international benchmark exercise on the measurement of fibre bed compaction behaviour. The aim was to identify aspects of the test method critical to obtain reliable results and to arrive at a recommended test procedure for fibre bed compaction measurements. A glass fibre 2/2 twill weave and a biaxial (±45°) glass fibre non-crimp fabric (NCF) were tested in dry and wet conditions. All participants used the same testing procedure but were allowed to use the testing frame, the fixture and sample geometry of their choice. The results showed a large scatter in the maximum compaction stress between participants at the given target thickness, with coefficients of variation ranging from 38% to 58%. Statistical analysis of data indicated that wetting of the specimen significantly affected the scatter in results for the woven fabric, but not for the NCF. This is related to the fibre mobility in the architectures in both fabrics. As isolating the effect of other test parameters on the results was not possible, no statistically significant effect of other test parameters could be proven. The high sensitivity of the recorded compaction pressure near the minimum specimen thickness to changes in specimen thickness suggests that small uncertainties in thickness can result in large variations in the maximum value of the compaction stress. Hence, it is suspected that the thickness measurement technique used may have an effect on the scatter

Product Design Review Application Based on a Vision-Sound-Haptic Interface

Most of the activities concerning the design review of new products based on Virtual Reality are conducted from a visual point of view, thus limiting the realism of the reviewing activities. Adding the sense of touch and the sense of hearing to traditional virtual prototypes, may help in making the interaction with the prototype more natural, re- alistic and similar to the interaction with real prototypes. Consequently, this would also contribute in making design review phases more effective, accurate and reliable. In this paper we describe an application for prod- uct design review where haptic, sound and vision channels have been used to simulate the interaction with a household appliance

Use of Interactive Virtual Prototypes to define product design specifications: a pilot study on consumer products

Virtual Prototyping (VP) aims at substituting physical prototypes currently used in the industrial design practice with their virtual replica. The ultimate goal of VP is reducing the cost and time necessary to implement and test different design solutions. The paper describes a pilot study that aims at understanding how interactive Virtual Prototypes (iVPs) of consumer products (where interaction is based on the combination of haptic, sound and 3D visualization technologies) would allow us to design the interaction parameters that concur in creating the first impression of the products that customers have when interacting with them. We have selected two commercially available products and, once created the corresponding virtual replica, we have first checked the fidelity of the iVPs by comparing them with the corresponding real products, when used to perform the same activities. Then, differently from the traditional use of Virtual Prototypes for product design evaluation, we have used them for haptic interaction design, i.e. as a means to define some design variables used for the specification of new products: variations are applied to iVP haptic parameters so as to test with final users their preferences concerning the haptic interaction with a simulated product. The iVP configuration that users liked most has then been used for the definition of the specifications for the design of the new product

Virtualization of Industrial Consumer Products for Haptic Interaction Design

The haptic feedback perceived during the interaction with consumer products is an important aspect since it concurs in creating, together with the aesthetic features and sonic feedback, the emotional response during the first contacts with a product. And this may be decisive for the user’s decision of purchasing a product instead of another one. So the design of the haptic behavior of interaction elements of products can be both a suc- cessful strategy for capturing consumers’ attention but even a need for avoiding problems during the use. The paper describes the process of virtualization of the interaction with an industrial consumer product by means of haptic, sound and visualization technologies in order to obtain a prototype (interactive Virtual Prototypes) useful to design and test the haptic feedback of inter- action elements directly with end users

Application of functionally graded adhesives in aluminium-composite joints

Adhesive joints are characterized by non-uniform distribution of stresses and strains along the bond-lines, with maximum values near the ends of the overlaps. This phenomenon can cause the premature failure of the joints, being specially critical when brittle or semi-brittle structural adhesives are considered. This has motivated the research in the field of ‘functionally graded adhesive’ (FGA) or ‘multiple-adhesive’ joints, which reduce the phenomena described through a combination of rigid and brittle adhesives with more flexible and ductile ones. In this way, these strategies allow to notably increase the joints maximum load capacity. In this field, this article presents the work carried out by ITAINNOVA within the project SAFEJOINT. Specifically, the potential of the techniques based on ‘banded’ gradings as approximations of the continuum gradings is analysed. The study is focused in aluminium-composite single lap shear (SLS) joints with epoxy adhesives. The work done covers both the numerical optimisation of the joints and the fabrication and testing of samples in order to verify experimentally the potential for improvement of the technique comparing with mono-adhesive joints. Finally, an example of application of the technology is presented

Simulation strategy to compensate spring-in deformations in aeronautical panel made by liquid resin infusion

Spring-in in composite manufacturing is a relevant non desired effect that complicates the industrialization process of new composite parts. Geometrical deviations of the part with regard to the nominal dimensions  hinders posterior assembly operations or even can cause unconformities (part rejection). Although some correction operations may be introduced in the assembly method to absorb these deviations, a preferred approach is to compensate the tool geometry to produce the part within tolerances. This contribution presents a methodology that, in an iterative process, links a MEF simulation workflow for the prediction of process induced distortions, a routine to compute deviations and updating tool cavity surface, till the deviations are within a target tolerance. The spring-in calculation engine is implemented in Abaqus Standard with specific subroutines to model resin curing kinetics, heat generation, cure dependent mechanical constitutive model with consideration of thermal expansion and cure shrinkage, and specific strategies to simulate the tool/part interactions. The spring-in engine is incorporated in an external Python manager in charge of post-processing results, updating the mesh and launching the executions. This methodology aims at proposing a modified tool surface geometry that could be used to build a compensated tool at first, reducing industrialization time and cost

Analysis of mixed adhesive joints considering the compaction process

Incorporating a material properties variation along the bondlines has proved to be a useful method for improving adhesive joints performance. In this work, the potential of the technique is analysed for a single lap joint using the mixing adhesives approach. In order to include the compaction process effect in the structural analysis during the joint assembly, a computational fluid-dynamic model capable of integrating different resins along the bondline has been developed. Then, the results obtained from this model are mapped into a finite element model through an application developed for this purpose. Several parametric studies have been carried out comparing different configurations in terms of maximum load capacity of the joints. Finally, one of these joints configurations has been manufactured using a special device developed for assembling these mixed adhesive joints and tested. This banded configuration have shown both numerically and experimentally an ultimate load improvement of over 70%