Laboratory for the Technological Innovation of Structures and Materials LITEM

Colon, Spain

Laboratory for the Technological Innovation of Structures and Materials LITEM

Colon, Spain

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Perez M.A.,Laboratory for the Technological Innovation of Structures and Materials LITEM | Perez M.A.,Ramon Llull University | Oller S.,International Center for Numerical Methods in Engineering | Oller S.,Polytechnic University of Catalonia | And 3 more authors.
Composites Part B: Engineering | Year: 2015

This paper deals with modelling the effect of low-velocity impact damage upon the vibration response of CFRP laminates through a micro-mechanical description of the induced internal damage. The serial-parallel (SP) continuum approach is used to estimate the map of induced internal damage by considering the micro-structural interaction between the composite constituents and modifying their constitutive performance through a continuum damage formulation. An eigenvalue analysis is then done to determine the modal response of impacted laminates. The validity of the modelling approach to successfully reproduce the vibration response of impacted coupons is assessed through a comparison with an experimental test series conducted on a set of 48 CFRP laminated coupons. The results confirm the ability of the described approach in comparison to competing ones used to reproduce the experimentally observed behaviour. © 2015 Elsevier Ltd. All rights reserved.


Perez M.A.,Ramon Llull University | Manjon A.,Guitar Maker | Ray J.,Guitar Maker | Serra-Lopez R.,Polytechnic University of Catalonia | Serra-Lopez R.,Laboratory for the Technological Innovation of Structures and Materials LITEM
Journal of Cultural Heritage | Year: 2016

Guitar FE09 - MDMB 626 is one of the best-known Antonio de Torres instruments and is an excellent sounding example of a guitar with tornavoz. Although the instrument is in playable conditions, the back plate has a deformation and cracks which are undoubtedly the result of the pressure exerted by the tornavoz supports. Over the last hundred years experts have chosen not to have the cracks repaired as it might result in a change in the sound. Recently, professionals stated that the guitar sounded different with strips of masking tape covering the cracks. Although subjective evaluations and claims abound, no quantitative data is available to determine the effect of this modification. This paper provides the results of an experimental campaign aimed at assessing the effect upon the vibration response of this eventual non-invasive intervention. Vibration testing was performed on the top and back plates before and after adhering strips of masking tape along the cracks. The influence of tensioning the strings is also examined. Correlations were done in both modal and frequency domains. The results allow conclusions to be drawn regarding the influence of this simple non-invasive intervention that can lead to audible changes, proving the feasibility of using vibration-based NDT methods for damage or structural modification assessment of musical instruments. © 2016 Elsevier Masson SAS.


Neagoe C.A.,Polytechnic University of Catalonia | Neagoe C.A.,Laboratory for the Technological Innovation of Structures and Materials LITEM | Gil L.,Polytechnic University of Catalonia | Gil L.,Laboratory for the Technological Innovation of Structures and Materials LITEM | And 2 more authors.
Construction and Building Materials | Year: 2015

Recent developments in the design of advanced composite materials for construction have led researchers to create novel high-performance structural elements that combine fiber-reinforced polymer (FRP) shapes with traditional materials. The current study analyzes the experimental structural response of eight hybrid beams made of pultruded glass FRP (GFRP) profiles mechanically connected to reinforced concrete (RC) slabs, suitable for building floors as well as footbridge and marine pier superstructures. The influence of partial interaction is studied by considering a low degree of shear connection and an analytical assessment of the whole response is carried out using previous formulations, highlighting a good accuracy. The behavior of the hybrid beams is further evaluated against that of equivalent reinforced concrete beams and single GFRP profiles, thus proving the feasibility of the solution. © 2015 Elsevier Ltd. All rights reserved.


Perez M.A.,Laboratory for the Technological Innovation of Structures and Materials LITEM | Perez M.A.,Polytechnic University of Catalonia | Martinez X.,International Center for Numerical Methods in Engineering | Martinez X.,Polytechnic University of Catalonia | And 8 more authors.
Composite Structures | Year: 2013

The impact damage tolerance of fiber-reinforced laminated composite materials is a source of concern, mainly due to internal induced damage which causes large reductions on the strength and stability of the structure. This paper presents a procedure based on a finite element formulation that can be used to perform numerical predictions of the impact induced internal damage in composite laminates. The procedure is based on simulating the composite performance using a micro-mechanical approach named matrix-reinforced mixing theory, a simplified version of the serial/parallel mixing theory that does not require neither the iterative procedure nor the calculation of the tangent stiffness tensor. The numerical formulation uses continuum mechanics to simulate the phenomenon of initiation and propagation of interlaminar damage with no need to formulate interface elements, resulting in a computationally less demanding formulation. To demonstrate the capability of numerical procedure when applied to a low-velocity impact problem, numerical results are compared with the experimental ones obtained in a test campaign performed on 44 laminates specimens subjected to an out-of-plane and concentrated impact event, according to ASTM test method. Results are in good agreement with experimental data in terms of delamination onset and the internal spatial distribution of induced damage. © 2013 Elsevier Ltd.


Neagoe C.A.,Polytechnic University of Catalonia | Neagoe C.A.,Laboratory for the Technological Innovation of Structures and Materials LITEM | Gil L.,Polytechnic University of Catalonia | Gil L.,Laboratory for the Technological Innovation of Structures and Materials LITEM
Composite Structures | Year: 2015

Hybrid beams made of pultruded fiber-reinforced polymer (PFRP) shapes connected to reinforced concrete (RC) slabs are regarded as novel cost-effective and structurally-efficient elements. The current study addresses the need for a robust analytical procedure for the design of such members considering the structural implications of shear interaction effects. The discussed analytical procedure is based on the Timoshenko beam theory and on the elastic interlayer slip model extended from steel-concrete and timber-concrete composite beams, and presents the necessary mathematical tools for evaluating deflections, flexural capacities and stress distributions of hybrid beams. Partial interaction effects are quantified by using a proposed dimensionless parameter that depends mainly on the connection's stiffness. The analytical equations were validated successfully against available experimental data and conclusions indicate that the simplified model for partial interaction is viable and should be used even for specimens with full interlayer shear capacity. © 2015 Elsevier Ltd.


Perez M.A.,Laboratory for the Technological Innovation of Structures and Materials LITEM | Perez M.A.,Polytechnic University of Catalonia | Gil L.,Laboratory for the Technological Innovation of Structures and Materials LITEM | Gil L.,Polytechnic University of Catalonia | And 4 more authors.
Composite Structures | Year: 2014

This paper presents the results of an extensive experimental campaign aimed to examine the effect upon the vibration response and on the residual load-bearing capacity caused by both: isolated artificially induced interlaminar damage and low-velocity impact induced damage in composite laminates. The experimental programme included modal testing, drop-weight impact testing, ultrasonic inspection, transverse quasi-static loading testing and compression testing conducted on a set of 72 carbon fibre-reinforced composite laminated coupons. Both types of damage caused measurable changes in laminate performance, however marked divergent trends were observed. The results allowed for conclusions to be drawn regarding the adequacy of the artificial damage approach and highlighted the importance and role of other forms of degradation upon damage tolerance of laminated composites containing damage. © 2014 Elsevier Ltd.


Perez M.A.,Laboratory for the Technological Innovation of Structures and Materials LITEM | Perez M.A.,Polytechnic University of Catalonia | Gil L.,Laboratory for the Technological Innovation of Structures and Materials LITEM | Gil L.,Polytechnic University of Catalonia | And 2 more authors.
Composite Structures | Year: 2014

Due to the problems arising from impact damage in composite laminates, there is a need to develop fast, accurate, cost-effective and non-destructive testing methods to identify this type of damage at an early stage and thus enhance the service life of composite structures. This paper presents the results of an extensive experimental campaign conducted to investigate the feasibility of using vibration-based methods to identify damages sustained by composite laminates due to low-velocity impacts. The experimental programme included an evaluation of impact damage resistance and tolerance according to ASTM test methods, characterisation of induced damage by ultrasonic testing and quantification of the effects on the vibration response. The damage identification involved the detection, localisation, quantification and estimation of the remaining bearing capacity. Four damage indicators based on modal parameters were assessed by comparing pristine and damaged states. The results allowed for conclusions to be drawn regarding the capability and suitability of each damage indicator, including its ability to detect impact-induced damage, its precision in determining the location of damage, its sensitivity regarding damage extent and pertinent correlations with residual bearing capacity. © 2013 Elsevier Ltd.

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