Design of a Blast Resistant Armour Plate Søren Barrett Rasmus V.L.R. Christiansen Ahmad Othman M.Sc. Thesis Aalborg University June 2017 Department of Materials and Production Department of Materials and Production Fibigerstræde 16 DK 9220 Aalborg Øst www.ses.aau.dk Synopsis: Title: This thesis treats blast effects on a generic Designofablastresistantarmour armour floor panel with prioritised focus on plate the military applications more specifically the Humvee. The purpose of this thesis is to deter- mine the blast load from an explosive placed Project period: below the vehicle, investigate the material pa- DMS4, Spring semester 2017 rameters of an aluminium foam for implemen- tation in an armour solution, and suggest a generic armour panel maximising energy ab- Project group: sorption for protection of the personnel in the 1.123c vehicle. Initially, the case of the thesis is pre- sented along with the thesis scope and outline. Group members: This is followed by general theory as a basis for the remainder of the thesis. The blast load, peak pressure and impulse, from a DM51 hand SørenBarrett grenade exploding beneath a floor panel of the vehicle is determined using two different meth- ods. Both methods are based on empirically RasmusV.L.R.Christiansen obtained data in grand test schemes, and are therefore validated for a large variety of cases. Theinvestigationoftheenergyabsorbingprop- erties of the aluminium foam shows that the AhmadOthman available foam is highly inhomogeneous and in- convenient for design tasks requiring great tol- Supervisors: erances. An alternative is therefore investi- Jørgen Asbøll Kepler gatedusingahighlymodifiablestructureoflat- tices for designs requiring great material con- ECTS: trol. However, the cost of the aluminium foam 30 makes it highly desirable for structures cover- ing a large area, and analytical as well as nu- Number of pages: merical models are developed for determining 106 + (46) effective designs utilising the foam. Different design concepts are investigated, morphed and Annex: rejected until a single design is optimised for ZIP-archive energy absorption and use in the armour floor panel of the vehicle. Finally, plans for experi- Submission date: mental validation of both the analytical meth- 2016-06-02 ods and the final design are described. Preface ThisthesishasbeensubmittedtotheDepartmentofMaterialsandProductionatAalborg University in partial fulfilment of the requirements for the M.Sc. degree on the study; Design of Mechanical Systems. The thesis period was from the 1st of February to the 2nd of June 2017. The work has been supervised by Associate Professor, Ph.D. Jørgen Asbøll Kepler to whom we would like to extent our thanks for guidance, discussions and feedback throughout the period. Furthermore, we would like to thank the cooperating partner Composhield A/S for the project, materials, guidance and discussions and espe- cially a thank you to the company representative Herluf Montes Schütte. The studies have made use of the commercial softwares MATLAB and ANSYS Autodyn and ANSYS explicit dynamics. The report is typeset in LATEX, and figures are made in MATLAB or Microsoft Visio. Furthermore, the terminal ballistics laboratory in the basement of Fibigerstræde 14, Aalborg University has been used for experiments. Appended to the thesis is an appendix in which additional information or explanations can be found. References to theses appendices exist throughout the report, when neces- sary. An electronic annex containing ANSYS simulation files, MATLAB files, material tests etc. are likewise appended, and can be found in the project database. References in the report are made using the Harvard method, meaning the authors of the reference along with the year the material is published are stated in the report as [Author, year]. Additional information on the material is listed in the bibliography sorted by the last name of the first author. The report is intended for supervisor, censor and Composhield. The content of the report and project is non-classified, but subjected to a Non-Disclosure Agreement between the authors and Composhield. Søren Barrett Rasmus V.L.R. Christiansen Ahmad Othman Aalborg, June 2017. iii Abstract The objective of the present M.Sc thesis is to propose a design for a blast resistant armour floor panel for vehicles in military applications. The project is conducted in cooperation with Composhield A/S, a military armour manufacturer, who aim to enhance their al- ready extensive product portfolio within lightweight protection panels supplying greater protection of their clients in theatres of operation around the world. The proposed design is an amour floor panel with specifications offering protection against a blast load from an explosiveplaceddirectlybeneaththevehicleofequivalent0,12kgTNTatadistanceof0,5 m, i.e. the case-load. The panel does resist greater blast loads with slight modifications. A three-way approach to the problem is taken consisting of an analytical, a numerical and an experimental approach. Only the analytical and numerical approach are finished in the following report, while the experimental approach is planned for the near future. The analytical approach is utilised for obtaining a solid understanding of the governing blast parameters and an initial guess of different design parameters. This approach is mainly academical. The actual design of the armour panel is conducted purely numerically. One of the significant problems in the thesis is to determine or quantify the blast load actingonthefloorofthevehicleoriginatingfromanexplodingDM51handgrenadeof0,12 kgTNTatadistanceof0,5m. Anextensivestudyofblasteffectsisthereforeconductedin order to determine the design load on the structure acting as a load case for the remaining oftheproject. Thisisfollowedbyastudyofthematerialparametersoffoamedaluminium in order to determine the energy absorbing properties and ultimately the applicability in armour panels. Analytical studies in determining the deformation and the optimum distribution of front panel and foam mass for maximum energy absorption are conducted. However, the manufacturing methods of aluminium foams are very difficult to control while remaining cheap resulting in a, at times, highly inhomogeneous material which is unacceptable in some applications. An alternative using a lattice structure is therefore investigated, resulting in a highly modifiable structure which can be re-engineered for specific needs. A numerical design procedure using hydrocode is utilised in search of a capable design concept for blast loads which is the main focus of the thesis. The capable design is reached through a parametric study of multiple iterations minimising the residual load in the structure following the deformation of the armour panel. The experimental approach has not been conducted, but a plan for near future experimen- tal work is described in the report. This includes verification of discrepancies between the analytical and numerical approach, and a full-scale test of the armour panel for validation of the ability of the panel to withstand the specified blast threat. Abstract Formålet med det foreliggende speciale er at foreslå et design for en sprængningsresistent panser gulvplade for køretøjer i militære applikationer. Projektet er udført i samarbe- jde med Composhield A/S, en panserproducent for militære applikationer, som søger at udvide deres allerede omfattende produktkatalog indenfor letvægtsbeskyttelsespaneler til beskyttelse af deres klienter i verdensomspændende militære brændpunkter. Det fores- låede design er et panser gulvpanel med specifikationer, der tilbyder beskyttelse imod en sprængningslast fra en eksplosiv placeret direkte under køretøjet bestående af en ækvi- valent TNT-vægt på 0,12 kg i en afstand af 0,5 m, m.a.o. case-lasten. Panelet modstår større sprængningslaster med få modifikationer. En tredelt fremgangsmåde i forhold til problemet er taget, og består af en analytisk, en numerisk og en eksperimentel del. Kun den analytiske og numeriske del er færdig- gjort, men den eksperimentelle del er planlagt for den nære fremtid. Den analytiske del er udført for at opnå en solid forståelse af de bestemmende sprængningsparameter og et indledende gæt på designparametrene. Denne del er hovedsagelig medtaget grundet akademiske overvejelser. Den faktiske designproces er udført rent numerisk. Etafdesignifikanteproblemerispecialeteratbestemmeellerkvantificeresprængningslas- ten virkende på køretøjets gulvpanel fra en eksploderende DM51 håndgranat, hvilket pro- ducerer case-lasten. Et udførligt studie af sprængningseffekter er derfor udført for at bestemme designlasten virkende på køretøjet, som bruges igennem hele projektet. Dette er efterfulgt af et materialestudie i et tilgængeliggjort aluminiumsskum med det formål at bestemme de energiabsorberende egenskaber og ultimativt dettes anvendelighed i et panserpanel. Analytiske studier er anvendt for at bestemme deformationen i dette skum under last, og den optimale fordeling af masse i henholdsvis frontpladen og skummet for maksimal energioptag er ligeledes bestemt. Fremstillingsparametrene er dog meget krævende at kontrollere mens omkostningerne stadig holdes nede, og dette resulterer i et skum, der til tider er meget uhomogent, hvilket i en række designapplikationer er uacceptabelt. Et alternativ, der gør brug af en gitterkonstruktion, er derfor undersøgt resulterende i et design, der er yderst modificerbar til specifikke behov. En numerisk designproces, ved hydrocodes, er anvendt i forsøget på at finde et kompe- tent sprængningsresistent design, hvilket også er hovedfokusset for dette speciale. Det kompetente design er fundet igennem et parameterstudie over en række iterationer med optimeringskriteriet at minimere restlasten i strukturen efter deformation af panserpan- elet. Det eksperimentelle arbejde er ikke udført, men en plan for den nære fremtid er beskrevet i rapporten. Dette inkluderer en verifikation af de observerede afvigelser imellem de analytiske og numeriske modeller samt en fuldskala test af panserpanelet for validering af hvorvidt panelet er i stand til at modstå sprængningstruslen.