Lightweight titanium/polymer/titanium sandwich sheet for technical and biomedical application

Abstract

The development of biocompatible implants is remarkably increased by designing new alloys; mainly on the basis of titanium (Ti) and magnesium (Mg) for permanent and biodegradable alloys, respectively. Polymer-based composite structures were also developed and tested to match the conditions of human bones. In this paper, a sandwich material (SM) approach is introduced to tailor the biomechanical properties, mainly the elastic modulus (E) and the biocompatible properties. The sandwich material is composed of Ti grade 1 (Ti Gr. 1) cover sheets and a polypropylene copolymer (PP-PE) core (PP-polypropylene, PE-polyethylene). An epoxy resin is used as an adhesive agent. This type of sandwich material has the potential to replace commercially used laminates in aerospace and automotive industry in cases of the need of a formable lightweight product, too.The mechanical properties were characterized for different core thicknesses via tensile testing. The mechanical properties exhibited a good matching with the estimated values according to the rule of mixtures. On this basis, sandwich material can be tailored to give the appropriate density, elastic modulus and strength as well by varying the ratio of thickness between the partners. The forming behavior was examined under deep drawing conditions, where the Ti-sandwiches exhibit a good drawing capability; cups can be drawn close to the limits of the mono-metal sheet. 3-[4,5-dimethylthiazol-2-y1]-2,5-diphenytetrazolium bromide (MTT) cell viability assay was used to examine the behavior of human osteosarcoma MG-63 cells on metal and polymer components of sandwich material. Cell viability was much higher for Ti/PP-PE/Ti sandwiches compared to 316L/PP-PE/316L ones.Keywords: Sandwich / composite / titanium / PP-PE polymer / deep drawing / mechanical properties / biocompatibility Die Entwicklung biokompatibler Implantate fokussiert sich derzeit mit der Zielsetzung der Anpassung an die mechanisch-biologischen Anforderungen neben dem Einsatz von Werkstoffen auf keramischer oder auch polymerer Basis weiterhin auf die funktionsgerechte Auslegung metallischer Werkstoffe wie Titan oder Magnesium und ihren Legierungen. In diesem Bericht wird ein Sandwichverbund (sandwich material) vorgestellt, der eine maßgeschneiderte Anpassung der biomechanischen Eigenschaften ermöglicht, hier besonders der mechanischen Eigenschaften -wie den Elastizitätsmodul E -und Berücksichtigung der Biokompatibilität.

Resin-free three-layered Ti/PMMA/Ti sandwich materials: Adhesion and formability study

“…As stat ed befor e 23 , depending on t he t hickness rat io of t he mono-mat er ial s, it is possibl e t o design t he mechanical propert ies of t he ent ir e sandwich syst em, according t o t he Ro M. Thus, as an exa mpl e, wit h a high rat io of pol ymer t he yield and ult imat e t ensil e stresses (YS and UTS) as well as t he Young's modulus (E) can be r educed, in order t o r each pr opert ies comparabl e t o t hat of t he cort ical bone 50,51 . Indeed, consider ing t hat the chosen Ti sheet and PMMA foil have a…”

“…The t oxicit y of t his adhesive layer 29 evidently pr event s t heir a ppl icat ion in t he biomedical fiel d and food pr oduct ion. In our pr evious work 23 , it was shown t hat , following t he rul e of mixt ur es, t he mechanical pr opert ies of t he whol e sandwich can be ta il or ed according t o t he skin and cor e t hicknesses (or rather t heir volume fract ions) achieving sandwich configurat ions wit h desir ed pr opert ies. In t his way, structures wit h t he necessary and designed st iffness and strength can be pr oduced.…”

“…Ther efor e, by combining t hese t wo mat er ial s, structur es possessing new pr opert ies, such as h igh-energy absor pt ion, high corrosion and mechanical r esistance coupl ed wit h a l ight weight , can be fabr icat ed 22 . In part icular , layered structur es, such as sandwich mat er ial s, composed of t wo metall ic skin sheets and a pol ymer cor e can be an int er est ing alt ernat ive t o design innovative part s 23 . Such sandwich structur es are used in t he a ircraft , automot ive and naval industry because of t heir high acoust ic and da mping ca pacit y [24][25] , h igh st iffness and strength, good for mabil it y and l ight weight 20,[26][27][28] .…”

“…Such sandwich structur es are used in t he a ircraft , automot ive and naval industry because of t heir high acoust ic and da mping ca pacit y [24][25] , h igh st iffness and strength, good for mabil it y and l ight weight 20,[26][27][28] . In t hese syst ems, an epoxy r esin is commonl y used as an adhesive agent t o st ick t he pol ymer cor e onto the metal skin sheet s ensur ing good bonding between t he t wo component s even under shear load 23 . The t oxicit y of t his adhesive layer 29 evidently pr event s t heir a ppl icat ion in t he biomedical fiel d and food pr oduct ion.…”

Impact behaviour of 3-layered metal-polymer-metal sandwich panels

“…Focusing on steel metal sheets as reinforcement layers, some studies were proposed on panels made of high-grade austenitic stainless steel (316L) cover sheets and a core of a polyolefin (PP/PE), which is a polypropylene (PP) and polyethylene (PE) blend [6][7][8], or even with titanium cover sheets for biomedical or aviation applications [9]. A number of combinations in thickness and steel material were investigated to understand the influence of these material and geometrical changes on the forming limits of these hybrids compared to the metallic mono-materials [9].…”