Objective　Carbon　fiber　reinforced　plastics　(CFRP)　and　titanium　alloys　are　used　in　modern　equipment　owing　to　their　high　specific　strength,　corrosion　resistance,　and　fatigue　resistance.　Heterogeneous　joints　consisting　of　CFRP　and　metals　are　widely　used　in　the　aerospace　industry.　Laser　joining　of　CFRP　and　metals　has　recently　attracted　significant　interest　owing　to　its　high　joining　efficiency　and　superior　joining　quality　compared　to　mechanical　joining,　adhesive　bonding,　ultrasonic　welding,　etc.　Because　the　process　is　both　time-consuming　and　labor-intensive,　the　accurate　prediction　of　appropriate　process　parameters　is　highly　desired.　In　this　study,　a　realistic　three-dimensional　finite　element　model　is　developed　for　the　numerical　simulation　of　the　temperature　field　during　the　laser　joining　of　carbon-fiber　reinforced　polyetheretherketone　matrix　composites　(CFPEEK)　with　a　poly　ether　ether　ketone　(PEEK)　resin　matrix　and　TC4　titanium　alloy,　and　the　laser　joining　process　is　investigated.　Methods　A　fiber　laser　with　a　laser　wavelength　of　1070　nm　and　collimator　focal　length　of　200　mm　is　used　in　the　laser　joining　experiment　(Fig.　1).　A　rectangular　spot　is　obtained　by　beam　shaping　using　an　integrating　mirror,　with　a　focal　length　of　200　mm　and　a　spot　size　of　0.6　mm×5.8　mm.　The　laser　power　is　3500　W,　and　the　welding　speed　ranges　from　5　mm/s　to　40　mm/s.　The　dimensions　of　the　TC4　titanium　alloy　and　CFPEEK　are　60　mm×30　mm×2　mm　and　60　mm×25　mm×2　mm,　respectively.　The　CFPPEK　is　composed　of　a　PEEK　matrix　and　carbon　fibers.　The　carbon　fiber　layers　are　alternately　layered　with　PEEK　layers　and　have　a　0°/90°　cross-weave　(Fig.　2).　The　PEEK　layer　is　0.1　mm　thick　on　average,　and　the　carbon　fiber　layer　is　0.2　mm　thick　on　average.　Results　and　Discussions　A　three-dimensional　model　of　laser　joining　of　TC4/CFPEEK　is　established　based　on　the　fact　that　laser-induced　heat　input　is　transferred　to　the　bonding　interface　via　heat　conduction　and　actual　experimental　conditions.　The　grid　size　is　graded　to　improve　the　simulation　accuracy　while　maintaining　computational　efficiency　(Fig.　3).　Importantly,　in　the　CFPEEK　module,　the　PEEK　layer　thickness　(0.1　mm)　is　uniform　for　an　isotropic　homogeneous　material,　and　the　fiber　layer　thickness　is　uniform　(0.2　mm)　for　an　orthotropic　material　with　a　large　difference　in　the　thermophysical　characteristics　between　the　radial　and　axial　directions.　The　thermal　and　physical　parameters　of　the　TC4　and　CFPEEK　used　in　the　simulation　are　listed　in　Table　1.　It　is　worth　noting　that　the　thermal　conductivity　of　TC4　is　relatively　low,　and　it　is　therefore　difficult　to　obtain　the　maximum　melting　depth　in　both　TC4　and　CFPEEK　simultaneously　(Fig.　4);　thus,　the　experimental　and　simulation　results　of　TC4　and　CFPEEK　are　compared　separately.　The　results　reveal　that　the　temperature　field　distribution　obtained　by　the　numerical　simulation　agrees　well　with　the　experimental　results　(Figs.　5‒7).　Our　developed　model　is　then　used　to　estimate　the　temperature　field　distribution　as　a　function　of　laser　power　(Figs.　8　‒　10),　welding　speed　(Figs.　11　‒　14),　and　beam　size　(Figs.　15　and　16).　Finally,　a　simulation-predicting　laser　joining　process　window　is　provided　to　guide　the　parameter　selection　for　laser　joining　of　TC4　and　CFPEEK　(Fig.　17).　Conclusions　Considering　the　carbon　fiber　and　resin　distributions　in　CFPEEK,　a　more　realistic　finite　element　model　for　the　laser　joining　of　CFPEEK　and　TC4　is　developed.　In　this　model,　CFPEEK　is　composed　of　carbon　fiber　layers　and　resin　layers　that　vary　in　thickness.　The　resin　layer　is　isotropic,　whereas　the　carbon　fiber　layer　is　orthogonal.　This　model　is　used　to　investigate　the　effects　of　laser　parameters　on　the　temperature　field　of　the　joint.　The　accuracy　of　the　model　is　confirmed　by　the　experimental　results,　and　the　process　window　for　laser-joining　CFPEEK　and　TC4　is　predicted.　©　2023　Science　Press.　All　rights　reserved.